07-13
2023
SNC27P020 is a single-channel speech synthesis IC with 12-bit PWM direct-drive circuit, which integrates one input port and 8 I/O ports into a 4-bit microcontroller. Through the programming of the microcontroller in the SNC27P020, various applications of the user, including the synthesis of voice parts, the setting of key triggers, output control and other logic functions, can be easily realized. Note: SNC27P020 has no LVD function.feature of productWorking voltage: 2.1V~5.1V·System Clock: 2.304 MHz-1.5%·Duration: 20 seconds @6KHz ·RAM size: 128*4 bitsmaximum value. 64K*12 bit program size ·I/O Ports: - Input Port P9.0 Shared Reset Pin
07-06
2023
DC boost technology is an engineering technology that converts non-adjustable DC voltage into adjustable or fixed DC voltage. One method is to use the energy storage function of the inductor and the filtering function of the capacitor to boost the voltage; the other method is to use high frequency Oscillation generates low-voltage pulses, which are then boosted to a predetermined voltage by a pulse transformer, and then pulse rectification technology is applied to obtain high-voltage direct current. The DC step-up process is realized by a conversion circuit that controls electric energy by means of switching regulation, that is, a DC-DC converter. The core component of the DC-DC converter is a switching converter composed of a crystal diode, an energy storage device (or transformer), a capacitor and an inductor. Its output circuit rectifies the current through a low-pass filter composed of capacitors. Realize the output of high voltage direct current.The continuous update and improvement of DC boost technology has greatly affected the evolution of DC-DC converter topology. High power density, high efficiency, high performance, high reliability, low cost, and small size are the development directions of DC-DC converters. At present, DC boost technology has been widely used in battery-powered portable devices, high-power DC transmission technology, photovoltaic power plants and other fields, and has a good application prospect.1. Principle and analysis of DC boost circuitAs a DC-DC converter that converts DC into another fixed voltage or adjustable voltage, the DC boost circuit is used in DC drive systems, charging and storage circuits, switching power supplies, power electronic conversion devices and various electrical equipment. common application. Subsequently, various conversion circuits such as step-down circuits, buck-boost circuits, and composite circuits have appeared. According to the topology of the circuit, it is mainly divided into isolated and non-isolated circuits.1. Non-isolated circuitThe non-isolated topology includes BUCK circuit, BOOST circuit, CUK circuit, SEPIC circuit, etc. Among them, the BUCK circuit is a DC step-down circuit, and the BOOST step-up circuit is the most widely used, and it is also the basis of the latter two circuits. Therefore, this section focuses on the principle and characteristics of the BOOST boost circuit.The basic topology of the BOOST boost circuit is shown in the figure below. The switch in the actual circuit is generally an IGBT element (insulated gate bipolar transistor, which is composed of a BIT (bipolar transistor) and a MOS (insulated gate field effect transistor). Composite fully-controlled voltage-driven power semiconductor devices, which have both the advantages of high input impedance of MOSFET and low conduction voltage drop of GTK) or thyristor components, and the corresponding control signals are pulses based on PWM technology generator to provide.According to the analysis of the closing and opening of the switch s according to the analog circuit, combined with the basic knowledge of circuit theory, the output voltage can be deduced.To sum up, the boosting process of the BOOST circuit is the energy transfer process of the inductor. When charging, the inductor absorbs energy; when discharging, the inductor releases energy. If the capacitance is large enough, a continuous current can be maintained during the discharge of the output. If this on-off process is repeated continuously. A voltage higher than the input voltage can be obtained across the capacitor.The diode in the circuit is mainly used for isolation, that is, when the switch is closed, the voltage of the anode of the diode is lower than the voltage of the cathode, and the diode is cut off at this time, so that the energy storage process of the inductor does not affect the normal power supply of the output capacitor to the load: because in When the switch is turned off, the two superimposed energies supply power to the load through the diode. At this time, the diode is forward-conducting. It is required that the forward voltage drop should be as small as possible, so that more energy can be supplied to the load terminal as much as possible.The non-isolated DC-DC topology is relatively simple, the number of components required for the circuit is small, and it is easy to design and control, but it is also limited by the input-to-output voltage ratio, which cannot be applied to occasions with a large voltage conversion ratio, nor can it achieve Electrical isolation requirements, these topologies are suitable for low power equipment.2. Isolated circuitThe isolated topology mainly includes "flyback circuit", "forward circuit", "push-pull circuit", "half bridge circuit", "full bridge circuit" and related circuits derived from these basic circuits .The basic working process of this circuit is as follows: high-frequency oscillation generates low-voltage pulses—pulse transformer step-up to a predetermined voltage value—pulse rectification to obtain high-voltage direct current.Among them, the push-pull DC boost circuit is more widely used. At the same time, after the push-pull circuit is bridge rectified or full-wave rectified, the voltage ripple and current ripple of the output voltage are very small, so only a small energy storage is required. filter capacitor or energy storage filter inductor, an output voltage with very small voltage ripple and current ripple can be obtained. Therefore, the push-pull circuit is a switching power supply with very good output voltage characteristics.The main disadvantage of the push-pull circuit is that when the system works for a long time or often runs at high power, the circuit is prone to unbalanced magnetic flux, that is, the phenomenon of magnetic bias, and it is easy to burn out the shutdown tube and related devices. Another disadvantage of the push-pull circuit is that the switch tube of the circuit has a large turn-off withstand voltage value. Compared with other circuits, its withstand voltage must be greater than twice the working voltage. Therefore, push-pull circuits are rarely used at high voltage input.2. Application of DC boost circuitDC boost technology meets the demand for higher DC voltage during operation of equipment using DC power sources such as batteries, and has been widely used in mobile phones, pagers and other wireless communication equipment, camera flashes, portable security detectors, electric mosquito swatters, etc. application. At the same time, the development of high-power DC transmission technology, photovoltaic power generation technology, and uninterruptible power supply (UPS) technology is also inseparable from the application of DC boost technology.1. Application in LED driverIn the application circuits of electronic products such as mobile phones and digital cameras, it is usually necessary to drive the LED of the flash module or the LED of the display backlight through a boost circuit to adjust the brightness of the LED. The circuit for driving LED can generally be divided into two types: parallel drive and series drive. Parallel drive adopts the principle of capacitive charge pump voltage multiplication, and all LED loads are connected in series; series drive adopts the principle of inductive DC boost conversion (Boost circuit) to increase the total voltage of the system to meet the requirements of a single LED in series. The rated voltage demand of the load. The series drive circuit booster device is small in size, high in efficiency, and takes up less space, so it is widely used in mobile phones, digital cameras, PDA handheld devices, MP3 players, GPS receivers and other devices.The inductive DC boost conversion of series LEDs applies the Boost circuit boost principle, and the boost device MP1518 chip of Monolithic Power Systems (MPS) is well applied to mobile phones and other equipment. In addition, under the condition of a certain input voltage, the voltage across the drive LED is related to the duty cycle of the signal. The greater the duty cycle of the signal, the greater the output voltage, and the greater the brightness of the LED. In practical applications, a PWM wave is often added to the enable pin EN, and the brightness of the LED is adjusted by changing the duty cycle of the PM W wave.2. Application in solar photovoltaic power generation systemThe power generation principle of a solar cell is to utilize the photoelectric effect caused when it is incident on a semiconductor. The basic characteristics of photovoltaic cells are similar to diodes, which are completely different from traditional power generation methods. There is no rotating part of the rotor and no electromagnetic interaction is used. Therefore, the current generated by it is direct current. The photovoltaic power generation system mainly includes solar panels, chargers, batteries, controllers, DC boost circuits, inverters, etc.A typical photovoltaic power generation system consists of four parts: photovoltaic cell array, energy storage system, inverter, and DC control system. Among them, the electric energy emitted by single photovoltaic cells is very small, which is direct current. In order to meet actual needs and obtain a large enough power generation, it is necessary to connect single photovoltaic cells to form a battery pack, and then form a solar photovoltaic array by the battery pack. During the transmission and exchange of electric energy from the photovoltaic array to the energy storage unit, and then to your transformer unit, to maintain the efficient and safe operation of the system, a DC control system is required to adjust, protect and control the entire process.When the light is strong, the low-voltage direct current of the solar cell is directly provided to the DC boost circuit, and the battery is charged and stored through the charger; when the light is weak, the output power of the solar cell cannot meet the requirements of photovoltaic power generation. At this time, as an energy storage device The storage battery provides low-voltage DC power for the DC boost circuit, ensuring the continuity and stability of the photovoltaic power generation system. The DC boost circuit raises the low-voltage DC to 330V high-voltage DC, and then can get 50Hz/220V AC through the inverter. The output AC voltage and current are fed back to the controller through the detection circuit, and the controller can realize closed-loop control.3. Application in photomultiplier tubePhotomultiplier tubes are widely used in various photoelectric detection instruments. Similarly, in the field of biomedical engineering, photomultiplier tubes play an irreplaceable role in photoelectric imaging detection and treatment instruments (such as PET). The power supply of the early photomultiplier tubes was boosted by a power frequency transformer and then rectified by voltage doubling. This kind of power supply has a large volume and poor effect. At present, the high-voltage power supply of the photomultiplier tube adopts the DC converter method, which is smaller in size and higher in efficiency than the rectification scheme after boosting the power frequency transformer, and has a good application prospect.The input DC voltage is +12 V, the output voltage is adjustable, and the typical output voltage is +1200 V. Its main components are low-voltage DC power supply, PWM control circuit, power switch tube, high-frequency transformer, voltage doubler rectifier circuit, filter circuit and sampling feedback circuit. The +12 V DC input voltage provides working power for the control circuit and the transformer; the output signal of the PWM control circuit drives the power transistor to provide a low-voltage high-frequency square wave for the high-frequency transformer; the AC output signal of the high-frequency transformer is further obtained by a voltage doubler rectifier circuit Boost and rectify, output DC high-voltage signal: the high-voltage output signal is further filtered after passing through the filter circuit, effectively reducing the output ripple coefficient; the output voltage feedback circuit provides a voltage feedback signal for the PWM control circuit, through the pulse modulator The reference voltage of the error amplifier is compared to control the output pulse duty cycle of the pulse modulator, so as to achieve the purpose of regulating the output voltage.Summary of boost circuit technologyThis article describes the principles and applications of two main DC boost circuits. The BOOST circuit achieves the purpose of boosting the voltage through the switch tube and inductor energy storage. It is relatively simple, has high power density, low current, and uses a non-isolated topology; and because of this, it is itself a source of electromagnetic interference that may cause dysfunction of surrounding electronic equipment. The circuit using transformer boosting, represented by the push-pull DC boost circuit, adopts an isolated topology, and can further boost the voltage through the turns ratio and the subsequent voltage doubler rectifier circuit, which is more suitable for the input voltage. Low voltage, high voltage ratio, and isolation is required. The two have a wide range of applications based on their own characteristics. In the application circuits of electronic products such as mobile phones and digital cameras, it is usually necessary to drive the LED of the flash module or the LED of the display backlight through a boost circuit to adjust the brightness of the LED. In the photovoltaic cell, the low-voltage direct current converted from light by the direct current step-up circuit is charged and stored in the battery through the charger. Another example is that in the photomultiplier tubes widely used in various photoelectric detection instruments, the high-voltage power supply for the high-voltage electric field between the plates adopts the DC converter method, which is smaller than the rectification scheme after boosting the power frequency transformer. ,efficient.The above is the principle and application of the DC boost circuit introduced by Shenzhen Zuchuang Microelectronics Co., Ltd. If you have software and hardware function development needs for smart electronic products, you can rest assured to entrust them to us. We have rich experience in customized development of electronic products, and can evaluate the development cycle and IC price as soon as possible, and can also calculate PCBA quotations. We are a number of chip agents at home and abroad, including MCU, voice IC, Bluetooth IC and modules, wifi modules. We have hardware design and software development capabilities. Covering circuit design, PCB design, single-chip microcomputer development, software custom development, APP custom development, WeChat official account development, voice recognition technology, Bluetooth wifi development, etc. It can also undertake the research and development of smart electronic products, the design of household appliances, the development of beauty equipment, the development of Internet of Things applications, the design of smart home solutions, the development of TWS solutions, the development of Bluetooth audio, the development of children's toys, and the development of electronic education products.
07-19
2023
Inkjet printing is also called inkjet printing. As a printing process, it can be used for graphic transfer like lithography and screen printing. Inkjet printing is a non-contact physical printing process. It does not need to use chemical potions, and it does not use printing plates or films to print like movable type printing and exposure photography. It only needs to output the printed graphics directly from the computer and control them through the controller. The nozzle of the inkjet system ejects ink particles from the nozzle to form a pattern. The manufacturing process of the traditional PCB circuit is very complicated. It needs to go through the image transfer process, make the metal adhere to the substrate, form the etching manufacturing process of the circuit, and finally appear the desired circuit on the substrate. The current image transfer technology has reached the limit of the line width, and can no longer increase the packaging density. In contrast, using inkjet technology, there is no need to change the production line and prepare components, and only need to directly input the CAD data into the inkjet printing device to achieve the purpose of changing the line. However, the current inkjet technology for printed circuit boards is only limited to a certain step in the numerous manufacturing processes of printed circuit boards, and cannot fundamentally solve the many serious chemical problems of printed circuit board products due to the lengthy process. Pollution, waste gas pollution, high energy consumption and other environmental issues.1. Technical scheme of full inkjet manufacturing of circuit boardsThe full inkjet manufacturing method of the circuit board is to first print the conductive layer, insulating layer, interlayer via hole, solder mask and protective layer on the carrier board according to the computer output graphics, and then print the character layer, components, etc., through layer by layer printing technology, and finally realize the full inkjet manufacturing of the entire circuit board. This technical method can greatly shorten the manufacturing and processing process of printed circuit boards, shorten the original dozens of technological processes to only a few technological processes, and reduce the cost of resources such as production plants, personnel and supporting facilities. Invest in waste. The product processing of this technology does not involve any chemical potion and gas, no waste liquid and waste gas are produced, and meets the national environmental protection requirements. Carbon saving concept. This technical method is also applicable to the processing of metal-based circuit boards, thick copper printed circuit boards, embedded capacitance embedded resistance circuit boards, semiconductor IC substrates and other products, including integrated circuits of various organic and inorganic electronic components, such as electrodes, transistors, etc. , inductors, capacitors, resistors, batteries and other functional components.2.The technical steps of the full inkjet manufacturing method of the circuit board(1) According to the layout design requirements of the circuit board, prepare a carrier board with the same size and place it in the inkjet printer;(2) Input the inner circuit pattern into the inkjet printer through the computer, print the circuit pattern with conductive ink, and print out the non-circuit pattern area with insulating resin ink to manufacture a single-layer inner circuit board;(3) After the inner circuit board is heat-pressed and leveled, heat-cured or light-cured, repeat steps 1 and 2 to form a multi-layer inner circuit with a conductive layer, a via hole and an insulating layer whose thickness meets the design requirements plate;(4) Separate the multi-layer inner layer circuit board and the carrier board, and the special function carrier board may not be separated;(5) Use conductive ink to inkjet print the outer conductive layer pattern of the circuit board on the upper and lower surfaces of the multilayer inner layer circuit board, and perform hot pressing leveling and heat curing or light curing treatment;(6) Use solder resist ink and protective ink to inkjet print the solder resist pattern and protective pattern on the surface of the outer circuit board, and perform hot pressing leveling and heat curing or light curing treatment;(7) Use character ink to inkjet print character marking patterns on the surface of the finished circuit board, and perform heat curing or light curing treatment;(8) Carry out appearance processing on the printed circuit board to form the final multi-layer printed circuit board;(9) Various other inorganic and organic electronic functional structural materials can also be integrated into circuit boards by this method.The carrier board in the scheme can be made of paper, metal, glass, ceramic or resin materials, and flexible or rigid materials can be selected according to functional requirements. The inkjet printer can be a common household printer, such as an improved Epson printer. Different types of inks are output according to the colors designed by the computer, and are placed in the corresponding printer cartridges to ensure good printing efficiency. Among them, the conductive ink can use nano-silver or nano-copper and its oxide conductive ink; the insulating ink can use epoxy resin, polyphenylene ether, polyimide, etc. and its modified resin ink; solder resist ink and character ink are both Ordinary epoxy resin-based solder resist and character inks; protective inks are solder paste-based soldering inks. For the hot pressing leveling, a temperature-controlled electric iron can be used for hot pressing leveling of the semi-finished circuit board to ensure a flat and good printing interface. The appearance processing adopts methods such as laser cutting or mechanical cutting. The thickness of the conductive layer is 2-20 μm, the height of the via hole is 5-50 μm, the thickness of the insulating layer is 5-75 μm; the heat curing temperature is 80-200 ° C, and the time is 2-60 min; the light curing type is UV light curing , the curing time is ~30 min; the hot-press leveling temperature is 50~100°C, and the pressure is 1~50 kg.3. Implementation effect of full inkjet manufacturing of circuit boardsProvide a technical method for full inkjet manufacturing of circuit boards (as shown in Figure 1). This method can not only accurately control graphics, is easy to operate, greatly shortens the circuit board processing process, and does not involve any chemical liquid or gas process, so It is a low-carbon, energy-saving, and environmentally friendly printed circuit board manufacturing process that produces waste liquid and exhaust gas, while greatly reducing the waste of raw materials. It can make printed electronic circuits develop into a brand-new electronic processing process, a brand-new craft technology.With the continuous research and development of inkjet printing technology, inkjet printing technology has made great breakthroughs and progress. Especially in recent years, major breakthroughs and progresses have been made in inkjet printing machines, inkjet print heads, and inks, such as the super inkjet printing technology developed by the Japan Industrial Technology Research Institute, which can eject ink droplets as small as 1~2 pL device of. There are also UV curable jet printing inks suitable for large-scale production, especially the developed silver-containing nanoscale inks, which provide conditions for the production of PCB products with a line width/spacing as fine as 10-20 μm. In recent years, a more advanced super inkjet printing technology has been developed, the size of the jetted ink droplet can be as small as 1 μm or less, so that a line with a line width of less than 3 μm can be formed.SummarizeThe full inkjet manufacturing technology of circuit boards can easily achieve the purpose of energy saving and emission reduction without using expensive production equipment and environmental protection facilities. This method does not require a mask, and there is almost no "three wastes" in the production process, which improves environmental pollution and realizes green production. This technology can be applied to substrates such as rigid boards and flexible substrates, and can realize highly automated production methods, and multiple nozzles can operate in parallel, thereby increasing production capacity. It can be used in three-dimensional packaging and 3D circuit board manufacturing, and can realize the integration of active and passive functional parts. At the same time, due to the low melting point of metal nanomaterials, the curing temperature of metal lines is as low as 200~300°C. Because of these advantages, inkjet printing technology will be rapidly promoted and applied in the PCB industry, becoming the mainstream of PCB product production, and bringing revolutionary changes and progress to the PCB industry.The above is the full inkjet manufacturing method of the circuit board introduced by Shenzhen Zuchuang Microelectronics Co., Ltd. for you. If you have software and hardware function development needs for smart electronic products, you can rest assured to entrust them to us. We have rich experience in customized development of electronic products, and can evaluate the development cycle and IC price as soon as possible, and can also calculate PCBA quotations. We are a number of chip agents at home and abroad, including MCU, voice IC, Bluetooth IC and modules, wifi modules. We have hardware design and software development capabilities. Covering circuit design, PCB design, single-chip microcomputer development, software custom development, APP custom development, WeChat official account development, voice recognition technology, Bluetooth wifi development, etc. It can also undertake the research and development of smart electronic products, the design of household appliances, the development of beauty equipment, the development of Internet of Things applications, the design of smart home solutions, the development of TWS solutions, the development of Bluetooth audio, the development of children's toys, and the development of electronic education products.
07-13
2023
SNC27P332 is a single-channel speech synthesis IC with 12-bit PWM direct-drive circuit, which integrates one input port and 24 I/O ports into a 4-bit microcontroller. Through the programming of the microcontroller in the SNC27P332, various applications of the user, including the synthesis of voice parts, the setting of key triggers, output control and other logic functions, can be easily realized.FeaturesWorking voltage: 2.1V~5.1VSystem clock: 2.304MHz +-1.5%Voice duration: 332sec@6KHzRAM size: 192*4 bitMaximum program space 64K*12 bitI/O ports: - Input port P9.0, shared with reset pin - 24 I/O ports : P1, P2, P3, P4, P5, P6 - High drive/reverse current : P2, P3, P6 - Normal drive/reverse current : P1, P4, P5timer:- Timer 1: 2ms/4ms- Watchdog Timer (WDT): 110msIR output: P2.3 or P1.38 groups of hardware PWMIO: P2,P3,P6 - P3/P6 share the same PWMIOLow Voltage Reset (LVR)- Typical 1.9V Enable Disable Option- Low LVR current when low voltage reset (LVR) occursLow Voltage Detection (LVD)- 2 levels: 2.2V , 3.2V
07-12
2023
SNC27P040 is a single-channel speech synthesis IC with 12-bit PWM direct-drive circuit, which integrates one input port and 8 I/O ports into a 4-bit microcontroller. Through the programming of the microcontroller in the SNC27P040, various applications of the user, including the synthesis of voice parts, the setting of key triggers, output control and other logic functions, can be easily realized.feature of productWorking voltage: 2.1V~5.1VSystem clock: 2.304MHz +-1.5%Voice duration: 40sec@6KHzRAM size: 128*4 bitMaximum program space 64K*12 bitI/O ports:- Input port P9.0, shared with reset pin- 8 I/O ports : P2, P3- High drive/reverse current : P2, P3timer:- Timer 1: 2ms/4ms- Watchdog Timer (WDT): 110msIR output: P2.38 groups of hardware PWMIO: P2,P3Low Voltage Reset (LVR)- Typical 1.9V Enable Disable Option- Low LVR current when low voltage reset (LVR) occursLow Voltage Detection (LVD)- 2 levels: 2.2V , 3.2V
07-11
2023
feature of productWorking voltage: 2.1V~5.1V,System clock: 2.304MHz+-1.5%Voice duration: 85sec@6KHzRAM size: 128*4bitMaximum program space 64K*12 bitsI/O ports: - Input port P9.0 and reset pin -12I shared /O ports: P1, P2, P3 - High drive/receiver current: P2, P3 - Normal drive/receiver current: P1·Timer:-Timer 1: 2ms/4ms- Watchdog Timer (WDT): 110 ms·IR output: P2.3 or P1.38 sets of hardware PWMIO: P2, P3· Low Voltage Reset (LVR)-Typical 1.9V with enable/disable option- Low LVR current when LVR occurs. Low Voltage Detector (LVD)- 2 levels: 2.2V, 3.2V
07-10
2023
SNC27P168 is a single-channel speech synthesis IC with 12-bit PWM direct-drive circuit, which integrates one input port and 16 I/O ports into a 4-bit microcontroller. Through the programming of the microcontroller in the SNC27P168, various applications of the user, including the synthesis of voice parts, the setting of key triggers, output control and other logic functions, can be easily realized.Working voltage: 2.1V~5.1VSystem clock: 2.304MHz +-1.5%Voice duration: 168sec@6KHzRAM size: 128*4 bitMaximum program space 64K*12 bitI/O ports:- Input port P9.0, shared with reset pin- 16 I/O ports : P1, P2, P3, P6- High drive/reverse current : P2, P3, P6- Normal drive/reverse current : P1timer:- Timer 1: 2ms/4ms- Watchdog Timer (WDT): 110msIR output: P2.3 or P1.38 groups of hardware PWMIO: P2,P3,P6 - P3/P6 share the same PWMIOLow Voltage Reset (LVR)- Typical 1.9V Enable Disable Option- Low LVR current when low voltage reset (LVR) occursLow Voltage Detection (LVD)- 2 levels: 2.2V , 3.2V
07-07
2023
DDR high-speed line PCB design refers to the use of specific PCB (Printed Circuit Board, printed circuit board) design technology to achieve high-speed signal transmission when designing computer memory modules (such as DDR, DDR2, DDR3, DDR4, etc.). DDR (Double Data Rate) memory is a high-speed random access memory that can transmit two data points per clock cycle. In order to ensure the normal operation of DDR memory, special PCB design techniques must be adopted to deal with issues such as high-frequency signals, signal integrity, and electromagnetic interference.In the design of DDR high-speed line PCB, the following aspects are the key points to be considered:Length matching and delay control: The signal transmission speed on the DDR memory bus is very fast, so it is necessary to ensure that the lengths of the data and control lines match to prevent timing problems caused by different arrival times of the signals. In addition, by controlling the delay of the signal, the signal can reach the target device within the same clock cycle, so as to improve the performance of the system.Power supply and ground lead planning: In DDR high-speed line PCB design, good power supply and ground lead planning is very important. By properly planning the positions of the power supply and ground leads, electromagnetic interference and signal crosstalk can be reduced, and signal integrity can be improved.Signal integrity: The high-speed signal transmission of DDR memory requires high signal integrity. Therefore, in the PCB design process, technologies such as impedance matching, signal echo reduction, reasonable layout and wiring, and separation of signal and power layers are required to ensure signal stability and reliability.Interlayer interconnection and signal layer allocation: DDR high-speed lines usually adopt multi-layer PCB design to realize interlayer interconnection and signal layer allocation. Through reasonable layer stacking and signal layer allocation, signal crosstalk, electromagnetic interference, and transmission delay can be reduced, and system performance can be improved.Differential signal design: DDR memory uses differential signals to transmit data, so the layout, matching and routing of differential pairs need to be properly handled in PCB design. Differential signal design can improve anti-interference ability and transmission speed.In short, DDR high-speed line PCB design is a complex task, and factors such as signal integrity, timing requirements, electromagnetic compatibility, and anti-interference ability need to be considered comprehensively to ensure the stability and reliability of the DDR memory system.
07-05
2023
The development process of a product is a complicated and highly technical job, and a stable and reliable hardware platform with excellent performance is the foundation and guarantee of the company's product quality. Therefore, the process of hardware design work should follow certain standards and norms in order to meet the requirements of quality assurance. This paper focuses on the specification process of hardware design. It mainly includes the following contents: confirmation of hardware requirements, hardware system design, schematic diagram design, PCB design, prototype joint debugging and testing, project review and case closing.1. Confirmation of hardware requirementsBefore developing a product, first confirm the hardware requirements of the product. This information is usually provided by the customer in a very detailed document, and the business department of the company conveys the requirements to the development department. It is very important to understand user needs, because subsequent product solution selection, development plans, product inspection standards and other information come from this. This information includes: the target market for product application; all functions and performance standards that need to be met; the appearance size, mold and accessories of the product; the time of product demand.2. Hardware system designHardware system design, including selection of overall solution; confirmation of product mold appearance; formulation of project plan. According to customer needs, such as CPU processing power, storage capacity and speed, function and interface requirements, etc., select the appropriate overall solution. And to complete the selection of design schemes for key functional modules, the selection of key components, technical data, technical channels and technical support, fully consider technical feasibility, reliability and cost control. The selection of key components should follow the following principles:Unity: key function module devices, in the case of meeting the functional and performance requirements, try to choose module devices that have been used in other solutions within the company, and try to ensure the unity of peripheral circuits.Versatility: Try to choose pin to pin compatible components with a wide variety of components, as well as chips that have been widely used and verified in the market, and try to avoid choosing unpopular chips to reduce design risks.High cost performance: In the case of meeting the demand, try to choose low-cost components.Convenient procurement: Try to choose components that are convenient to purchase, have a short delivery period, and have no plans to stop production. The selection and design of molds should be as far as possible from the user's point of view, aesthetics, durability, safety, heat dissipation, cost, etc. are all issues that need to be considered. This work needs to be completed jointly by hardware engineers, structural engineers and art engineers. A realistic and rigorous project plan is a guarantee for product development in terms of time and efficiency. The project plan should not only take into account various uncertain factors that may arise, reasonably arrange the time schedule of each stage, but also ensure the work efficiency of the project personnel during the development process, so as to ensure that the product development is within the time required by the customer, and the quality and quantity are guaranteed in advance the completion.3. Schematic designThe design of the schematic diagram is fundamental to ensure the logical correctness of a product hardware. If there is a problem with the schematic design, it will cause the performance of some functional modules of the product to deteriorate or fail, and the system will be unstable or even unable to work if it is serious. The things to pay attention to in schematic design are roughly summarized as follows:When drawing the schematic diagram, try to use the company's standard component library package, and try to use the company's unified plan for the general function module design. The standardized schematic diagram design is easier to manage and review, and facilitates procurement and production control.General rules for schematic diagram design: According to the target market, determine the protection level of the schematic diagram for the part of the circuit that needs to be protected.Power supply system: At the beginning of the design, it is necessary to analyze in detail the current size required by each power supply in the board, accuracy requirements, ripple control, power-on sequence, etc. The design of the power supply must have sufficient margin, otherwise it will easily cause problems such as excessive heat generation of the power chip, insufficient output capacity of the power module, and malfunction of the system. Attention should also be paid to the separation of digital power and analog power.Cost control: Generally speaking, the greater the redundancy in the design, the more reliable the system will be, but the higher the cost will be; conversely, the smaller the redundancy will be, the lower the cost will be but the lower the reliability will be. The first version of the schematic diagram can reserve high design redundancy to ensure the stability of the system. At the same time, some compatible designs can be made to facilitate the cost reduction test in the subsequent debugging process, and finally achieve the most appropriate redundancy to make the product more cost-effective. optimize.Review: After the schematic design is completed, it needs to be sent to the chip provider for review, and the key modules are sent to the chip manufacturer for technical support review. The company should also organize strict review, especially for newly added functional modules, carefully review and demonstrate, in order to Ensure the correctness of the schematic diagram.Write design documents: 10-port connection methods related to software debugging, control status requirements, device addresses connected to the bus, etc., to facilitate subsequent software debugging.BOM production: Export the list of components, and make a BOM list according to the company's BOM standard format, indicating the code, type, detailed description, accuracy level, package size, assembly method, single-machine consumption, and bit number of each device. After completion, submit the sample plan quantity to the relevant personnel to check the inventory, and submit the purchase requisition if there is a shortage of materials. This part of the work should be done in advance, so as not to affect the development cycle due to the arrival time of materials.4. PCB designAfter the schematic diagram is completed, export the netlist and synchronize it to the PCB file. The packaging of PCB B should adopt the company's standard packaging as much as possible, and the new device packaging should read the chip manual carefully. Before starting PCB drawing, first ensure the correctness of all component packages.1. General steps and precautions of PCB designAccording to the selected mold, confirm the size of the motherboard, the position of all connectors related to mold assembly, height restrictions, areas where devices are prohibited, etc.Layout: The first principle of layout is to ensure the routing rate of the wiring, and place the devices of certain functional modules together as much as possible, but the interconnection between chips should pay attention to which devices should be placed close to which chip; digital devices and analog devices should be Separate and keep as far away as possible; heat-sensitive devices should be placed away from heat-generating devices; devices and wiring should not be placed near the positioning holes; decoupling capacitors should be as close as possible to the V c C of the device; when placing devices, consider subsequent debugging and soldering, not too dense; Consider the aesthetics of the entire board.2. General rules for wiringClock line and high-speed signal line: clock line and high-speed signal line are generally easy to be the interference source of electromagnetic radiation, so special attention should be paid to wiring. Generally divided into single-ended and differential. Generally, the single-ended line should be as short as possible, the formation or reference layer should be as complete as possible to reduce the loop, the ground cover should be complete and more ground holes should be drilled; the differential line should be complete in formation or reference layer, with equal length and equal distance. If there is an impedance requirement, the line width and line spacing should be calculated to reduce radiation.Important signal lines: pay attention to the treatment of ground cover, formation integrity and impedance control.Power line: According to the evaluation of the current of each power supply, the thickness of each power line can be set. Generally, the power line should be as thick as possible. The greater the current, the thicker the power line.Ground wire: To ensure the integrity of the ground plane as much as possible, the ground wire should be as thick as possible.Design inspection and review: After the P4 design is completed, use the inspection function that comes with the tool to check the spacing and connectivity to ensure that the spacing and connectivity are correct. Finally, after self-checking and optimization, send it to the chip provider to check the design, and send important modules to Corresponding technical support checks must also be carefully reviewed item by item within the company in accordance with standard procedures.Template file output and production: After the PCB design is completed, a board-making instruction file must be produced, including board thickness, board material, surface treatment method, characters, solder mask, board size and whether to assemble boards, quantity, impedance, etc. There will be a company's standard format for printed board factory production. At the same time, provide BOM files, coordinate files and silk screen drawings to the chip factory for sample mounting and welding.5. Sample joint debugging and testing1. Model joint debuggingAfter the hardware schematic diagram is designed, provide the schematic design document to the software personnel, so that they can start modifying the software according to their own hardware design in advance. After the sample mounting is completed, the software personnel will be handed over to the final software development work. During this period, the necessary hardware debugging will be carried out in cooperation with the software work. After all the functions required by the customer are completed, the hardware engineer will complete the remaining testing and confirmation. Work.2. Sample testTesting work can generally be divided into functional testing, performance testing and debugging, on-site testing and customer confirmation, and third-party certification testing.Taking the hardware requirements confirmation document as a guiding document, according to the requirements put forward by customers, hardware engineers conduct detailed tests and confirmations on all required functions and performance requirements, and perform software and hardware debugging for projects that do not meet the standards. The performance indicators not proposed by the customer are based on the relevant national standards and company testing standards.After the hardware engineer's testing and debugging is completed, it is submitted to the company's internal testing, and the group does a confirmation test to confirm whether the product meets all standard requirements in the laboratory. Due to the possible complexity and particularity of the target market environment, after the product self-test is completed, testers need to go to the target market site to conduct on-site multi-site testing. At the same time, communicate with customers to allow customers to make final confirmation of the product. According to customer requirements, if a third-party certification body is required to test, a prototype needs to be provided to the third-party certification body for certification testing and a certification report.6. Project review and closingOrganized by the project manager, the participants include the company's technical director, business personnel, software chief designer, hardware chief designer, testers and related senior technical personnel. Taking the technical requirements provided by customers as the guiding evaluation standard, and based on various internal design standards, testing standards, and auditing standards of the company, we conduct rigorous and detailed audits on various design documents, test reports and customer feedback of the project. Under the premise of ensuring that the product fully meets the customer's needs, evaluate and review the correctness, rationality, standardization, reliability and cost-effectiveness of the product design, and confirm whether the project meets the requirements and the case can be closed, and the relevant personnel participating in the project review Personnel sign and confirm one by one.Judging whether a project is successful is not only based on whether a design meets the requirements technically, but also whether the design is reasonable, whether the quality of the product passes the test, whether the cost of the product is properly controlled, and whether the completion time meets the needs. This requires efficient teamwork, detailed demand analysis, accurate solution selection, reasonable project planning, standardized design documents and rigorous project review, and a perfect hardware design process can precisely make these well connected, and it is also The guarantee of a good product design.The above is the hardware design and development process introduced by Shenzhen Zuchuang Microelectronics Co., Ltd. for you. If you have software and hardware function development needs for smart electronic products, you can rest assured to entrust them to us. We have rich experience in customized development of electronic products, and can evaluate the development cycle and IC price as soon as possible, and can also calculate PCBA quotations. We are a number of chip agents at home and abroad, including MCU, voice IC, Bluetooth IC and modules, wifi modules. We have hardware design and software development capabilities. Covering circuit design, PCB design, single-chip microcomputer development, software custom development, APP custom development, WeChat official account development, voice recognition technology, Bluetooth wifi development, etc. It can also undertake the research and development of smart electronic products, the design of household appliances, the development of beauty equipment, the development of Internet of Things applications, the design of smart home solutions, the development of TWS solutions, the development of Bluetooth audio, the development of children's toys, and the development of electronic education products.
07-04
2023
With the rapid development of electronic technology, electronic products are constantly updated. Since there are always various reasons for the failure of electronic products during the production process, there is electronic testing, and testing must be inseparable from testing systems.The test system is composed of multiple circuit boards. Once the circuit board fails, the system cannot work normally. Since each circuit board is expensive, it must be repaired if a fault occurs. The key to repair is analysis, and the process of analysis is the process of finding faults. Each circuit board is composed of one or more functional modules, and each functional module is composed of many components, and there are close connections between these components, so it is an important task to find faulty components. Very difficult thing.If you want to repair the circuit board, you must conduct in-depth research on the circuit board, fully understand the structure of the circuit board and the functions of each module; then there are maintenance methods, and good maintenance methods can make maintenance more effective.1. Maintenance method of circuit boardThe principle of circuit board maintenance method is to look first and then test, first easy and then difficult. The faulty circuit board must first be visually inspected to understand the fault phenomenon through visual inspection. Understanding the fault phenomenon will help to analyze the fault in the next step. The analysis process includes asking, watching, smelling, and measuring. The question is to ask the user about the failure, whether it is caused by improper use or a sudden failure during normal operation, and whether the circuit board has been repaired by others before and which components have been moved. The second thing to look at is to carefully observe the electronic components to see if there are obvious signs of discoloration and burnt, whether there are virtual soldering, reverse soldering, etc., and if necessary, you can use a magnifying glass to observe. Then smell, smell if there is any peculiar smell, once the integrated circuit (especially the high-power device) is burned out, it will smell like rotten eggs. The last thing is to measure is to measure, to analyze and find out the faulty device through measurement, and the measurement is divided into static measurement (that is, measuring the circuit board without power) and power-on measurement. The simplest measurement is to use a multimeter to measure the resistance between the power supply and the ground of the circuit board. Usually, the resistance of the circuit board should not be less than 70Ω. If the resistance is too small (only a few ohms or a dozen ohms), it means that there is Components are broken down or partially broken down.2. Classification of circuit board faultsThe scope of failure includes: local failure and global failure. Partial failure refers to the abnormal operation of one or several functional modules of the system; global failure refers to the operation status of the entire system.Faults are divided into stable faults and unstable faults. Stable refers to failures caused by functional failure of components, short circuits, etc.; unstable refers to: poor contact and poor function of components.3. The working principle of the circuit boardThis paper takes the DPS (measurement device voltage source) board as an example, its main functions are: (1) During the test process, it provides two device power supplies for the device under test according to the applied conditions, one of which has a voltage range of 0~50V, and the other The voltage application range is -50V~0V. (2) Measure the operating current of the device power supply, and the measured value is up to 5A.The device power supply board is composed of DPS1 and DPS2 two-way device power supply. Its main components are: logic control unit, decoding control unit, data converter, voltage and power amplifier, current clamp control unit, current sampling unit, differential amplifier , Relay control unit.The working methods of the DPS board are: pressurization (FV), pressurization flow measurement (FVMI). In the FVMI mode, the driving voltage value is provided to the input driver through the digital-to-analog converter, the output current is sampled by the sampling resistor, converted into a voltage value through the differential amplifier, and then the current value is read back by the analog-to-digital converter. The clamp value can be adjusted according to the load Setting, the clamping current plays the role of current limiting protection.The logical block diagram of the DPS board can be drawn by understanding the structure of the real diagram, as shown in Figure 3. Drawing a logic block diagram can make us understand its working process more clearly, which can provide great help for maintenance.Combined with the working principle and composition of the DPS board introduced earlier (the DPS board is composed of two circuits, one for positive voltage and one for negative voltage), we can see that these components provide positive and negative power supplies. Knowing this kind of information is very helpful for analyzing the circuit board. For example, if the positive voltage cannot be added on the DPS board, but the negative voltage can be added, the positive voltage can be repaired by referring to the negative voltage.When the DPS board fails, it is firstly detected statically. Since the integrated circuit uses direct coupling, there is a certain DC resistance between the other pins of the integrated circuit and the ground. This determined DC resistance is called the internal equivalent resistance of the pin, referred to as R, You can use a multimeter to measure the internal equivalent DC resistance of each pin to judge its quality. If the internal equivalent resistance R of each pin is in line with the standard (we can take a good integrated circuit and measure the internal resistance of each pin with a multimeter If the equivalent resistance R is used as the standard), it means that the integrated circuit is good; otherwise, if the difference from the standard value is too large, it means that there is a fault inside the integrated circuit. One point must be paid attention to when measuring, because there are a large number of non-linear components such as triodes and diodes inside the integrated circuit, it is not possible to judge whether a resistance value is measured in one direction during measurement, so the test leads must be exchanged and measured again to obtain positive and negative values. To the two resistance values, only when the forward and reverse resistance values in R meet the standard can it be concluded that the integrated circuit is intact.In the case where the fault source cannot be found in the static detection, only the DPS board is powered on for on-the-road maintenance. If you want to power on the DPS board, you must extend the DPS board, as long as you extend the DPS board, you can power on and analyze it.In actual maintenance, first measure the voltage of the pin when the power is on. If the voltage is abnormal, you can disconnect the pin connection and measure the voltage of the terminal to judge whether the voltage change is caused by the external components or inside the integrated block circuit; The DC equivalent resistance R between the external circuit and the ground is judged externally. Usually, the DC equivalent resistance (in-circuit resistance) between a pin of an integrated circuit and the grounding pin is measured in the circuit, which is actually the total DC equivalent resistance connected in parallel between R and R. In maintenance, the measurement method of on-circuit voltage and on-circuit resistance is often used in combination. Sometimes the on-circuit voltage and on-circuit resistance deviate from the standard value. It is not necessarily the damage of the integrated circuit, but the damage of the peripheral components that makes the R outside abnormal. , resulting in anomalous on-circuit voltage and on-circuit resistance. At this time, only by measuring the DC equivalent resistance inside the integrated circuit can we judge whether the integrated circuit is good or bad. According to actual maintenance experience, it is not necessary to solder the integrated circuit from the circuit board when measuring the internal DC equivalent resistance of the integrated circuit on the road, as long as the abnormal pin of the voltage or on-circuit resistance is disconnected from the circuit, and the grounding pin is connected to the circuit at the same time. The circuit board is disconnected, and the other pins remain as they are, and the positive and negative resistance values in R between the test pin and the ground pin can be measured to judge whether it is good or bad.4.Draw the circuit diagramNow many manufacturers do not provide the circuit diagram of the circuit board, but if you want to conduct power-on analysis on the circuit board, there is no way to conduct power-on analysis without the circuit diagram, so you have to draw the circuit diagram yourself. To draw a circuit diagram, you need to know the following points:(1) To understand the working conditions of related integrated circuits, first find out the signal input pins and signal output pins of the integrated circuits and the corresponding power pins and ground pins. The power supply pin of the integrated circuit is used to add the DC working voltage output by the rectification and filtering circuit to the internal circuit of the integrated circuit to provide DC power for the internal circuit of the integrated circuit; and the ground pin is used to connect the internal circuit of the integrated circuit The ground wire of the integrated circuit is connected with the ground wire in the circuit of the whole machine, so that the current of the circuit in the integrated circuit forms a loop. Therefore, the power pin and the ground pin are the two most basic and important pins for the normal operation of the integrated circuit.The signal input pin is connected to the circuit output pin of the previous stage, or connected to the signal source of the whole machine circuit, so that if you understand the signal input pin of the integrated circuit, you can move from the subsequent stage to the previous stage. for analysis. In many troubleshooting of circuit boards, for example: no voltage can be applied, no current can be applied, etc., only after the signal output pin of the integrated circuit is determined can the next step of maintenance be carried out, so find out the signal in the integrated circuit. Input and output pins are very important.(2) According to the manual of electronic components, write down the working characteristics of the IC (truth table, working characteristic curve, working voltage, input and output pins), and then simply arrange the positions of the relevant ICs according to the context of the structure diagram . Finally, use a multimeter to measure the relationship between the front and back stages of the IC, so that the connection between them can be simply drawn.5. Circuit board module unit1. Logic control unitThe logic control unit is the main control unit of the circuit board, which is equivalent to the "CPU" of the circuit board and is a programmable logic device. The main function is to control the relay unit, current clamp control unit and measurement unit by logic level.Failure analysis:(1) Since the level from the "logic control unit" is not enough to drive the relay, it must be driven by the drive circuit, so this should be taken into account when the relay does not work properly (logic control failure, drive circuit failure, failure of the relay itself).(2) When the system is powered on, if the "circuit board cannot be found" phenomenon occurs, it can basically be concluded that the logic control unit on the circuit board is faulty.2. Digital-to-analog converter (D/A)The digital-to-analog converter converts the digital signal given by the controller into an actual analog quantity to control external devices. When the DAC is working normally, the output analog voltage is proportional to the input digital quantity, so when the input and output are not proportional, it can be determined that the DAC is invalid.3. Current clampThe main function of the current clamp is to protect the subsequent circuit and the device under test. The current clamp on the DPS board is to protect the voltage and power amplifier of the subsequent stage. Because there are positive and negative power supplies on the DPS board, the clamping current should also have symmetrical positive and negative circuits.It can be seen from Figure 5 that the front stage connected to these two diodes is the clamping part, and the lower-stage operational amplifier circuit connected to this can be found. Use the diode characteristics of the multimeter to measure the relationship between the input and output of the lower-level op-amp circuit, and it can be known that the function of the op-amp circuit is to form a voltage follower. The voltage follower has the function of impedance transformation. The so-called impedance transformation function means that after being amplified by the voltage follower, its output voltage is approximately equal to the electromotive force of the signal source, but its output resistance is very small. This circuit is often used as an input stage, an intermediate stage, and an output stage. class.Fault analysis: When the DPS board is powered on, 5V is added and 5V comes out, but when it is added to more than 5V, it cannot be added (it is always 5V). At this time, the diode used for clamping the input stage of the follower can be removed. , power on again, if the detection returns to normal at this time, it means that the operational amplifier circuit used for clamping is faulty; if the fault persists, conduct reverse analysis to check the previous level, here it should be noted: as long as the current does not enter the closed loop, it can be Open the output pin of the op amp circuit for measurement.4. Current sampling unitCurrent sampling is composed of sampling resistors and relays with corresponding gears. Current measurement (MI) is the output current is sampled by sampling resistors. After sampling, it is converted into voltage through a differential amplifier, and then the current value is read back by an analog-to-digital converter.Fault analysis: The current is divided into many gears by the sampling resistor. If there is an error in a certain gear, first use a multimeter to statically measure the resistance of the sampling resistor. If the measurement is normal, then measure the relay of the corresponding gear. If the measurement is also normal, Then we have to look at the differential amplifier of the subsequent stage. If the measurement is normal, it can be concluded that the logic controller is faulty.6. Precautions for circuit board maintenanceBefore maintenance, anti-static work must be done first, such as wearing anti-static overalls and shoes, and wearing an anti-static wrist strap. The workbench for maintenance should also be treated with anti-static treatment, such as adding an anti-static table.Pay attention to the safety of electricity use, including the maximum bearing capacity of the circuit board when powering on and maintaining the circuit board; when you need to contact strong electricity, you must pay attention to personal safety and take measures to prevent strong electricity.With the continuous development of electronic products, the types and frequency of various equipment failures have also been greatly increased, so the requirements for maintenance personnel are also increasing, especially for those who are new to circuit board maintenance, many people are very confused at the beginning. I don't know where to start, and I don't know what to learn. In fact, if you want to learn circuit board maintenance well, you must have a certain foundation in digital electricity and analog electricity. Theory + method + practice + summary, so that we can deal with all kinds of faults that occur on the circuit board.The above is the maintenance method of the test system circuit board introduced by Shenzhen Zuchuang Microelectronics Co., Ltd. for you. If you have software and hardware function development needs for smart electronic products, you can rest assured to entrust them to us. We have rich experience in customized development of electronic products, and can evaluate the development cycle and IC price as soon as possible, and can also calculate PCBA quotations. We are a number of chip agents at home and abroad, including MCU, voice IC, Bluetooth IC and modules, wifi modules. We have hardware design and software development capabilities. Covering circuit design, PCB design, single-chip microcomputer development, software custom development, APP custom development, WeChat official account development, voice recognition technology, Bluetooth wifi development, etc. It can also undertake the research and development of smart electronic products, the design of household appliances, the development of beauty equipment, the development of Internet of Things applications, the design of smart home solutions, the development of TWS solutions, the development of Bluetooth audio, the development of children's toys, and the development of electronic education products.
07-03
2023
For a long time, designers often spend their energy on the verification of programs, electrical principles, parameter redundancy, etc., but seldom spend their energy on the review of PCB design, and it is often because of PCB design defects that lead to a large number of product performance issues. PCB design principles involve many aspects, including various basic principles, anti-interference, electromagnetic compatibility, safety protection, and so on. For these aspects, especially in high-frequency circuits (especially microwave-level high-frequency circuits), the lack of relevant ideas often leads to the failure of the entire R&D project. Many people still stay on the basis of "connecting electrical principles with conductors to play a predetermined role", and even think that "PCB design belongs to the consideration of structure, process and production efficiency". Many engineers also do not fully realize that this link should be the special focus of the entire design work in product design, and mistakenly spend their energy on selecting high-performance components, resulting in a significant increase in cost and little improvement in performance.1. High-speed PCB designIn product engineering, PCB design occupies a very important position, especially in high-frequency electrical design. There are some general rules and these are to be treated as general guidelines. Applying the design principles and skills of high-frequency circuit PCB to the design can greatly improve the success rate of the design.(1) Wiring design principles of high-speed circuit PCB1. Minimize logic fanout, preferably with only one load.2. Avoid using through-holes as much as possible between the output and receiving ends of high-speed signal lines, and avoid crossing pin patterns. Especially the clock signal line needs special attention.3. The signal lines of the upper and lower adjacent layers should be perpendicular to each other to avoid right-angle turns.4. The parallel terminated load resistor should be placed as close as possible to the receiving end.5. In order to ensure the minimum reflection, the length of all open lines (or lines without termination matching) must satisfy the following formula: Lopen——open line length (inches); trise——signal rise time (ns); tpd——line propagation Latency (0.188ns/in - per stripline characteristic).6. When the length of the open line exceeds the value required by the above formula, a series damping resistor should be used, and the series termination resistor should be connected to the pin of the output terminal as much as possible.7. To ensure that the analog and digital circuits are separated, AGND and DGND must be connected together through an inductor or ferrite beads, as close as possible to the A/D converter. 8. Ensure adequate decoupling of the power supply. 9. It is best to use surface mount resistors and capacitors.(2) Bypass and decoupling1. Before selecting a decoupling capacitor, calculate the resonant frequency requirement required to filter high-frequency currents.2. Above the self-resonant frequency, the capacitor will become inductive, thus losing the role of decoupling capacitor. It should be noted that some logic circuits have spectral energy higher than the self-resonant frequency of common decoupling capacitors.3. The resonant frequency of the container itself is called self-resonant frequency. If you want to filter out high frequencies.4. Calculate the required capacitance value based on the RF energy contained in the circuit, the rise time of the switching circuit, and the frequency range of particular interest, rather than guesswork or conventional usage.5. Calculate the resonant frequency of the ground and power planes. The decoupling capacitor constructed on such two planes can achieve maximum benefit.6. For high-speed components and areas with rich RF bandwidth energy, multiple capacitors should be connected in parallel to remove RF energy with a large bandwidth. Also note: when the large capacitor becomes inductive at high frequencies, the small capacitor remains capacitive, and an LC resonant circuit will be formed at a special frequency, resulting in infinite impedance, thus completely losing the bypass function. When this happens, it is more efficient to use a single capacitor.7. Set parallel capacitors on all power input connectors of the circuit board and on the power pins of components whose rise time is faster than 3ns.8. At the diagonal direction of the PCB power input terminal and the wrench, a capacitor with a large enough capacity should be used to ensure the current change when the circuit switches states. The same consideration should be given to the decoupling capacitors of other circuits, the greater the operating current, the greater the required capacitance. To reduce voltage and current pulsation and improve system stability. Therefore, the decoupling capacitor shoulders the dual functions of decoupling and freewheeling.9. If you use too many decoupling capacitors, it will draw a lot of current from the power supply when it is turned on, so a group of large capacitors should be placed at the output of the power supply to provide a large amount of current.(3) Impedance transformation and matching1. In low-frequency circuits, the concept of matching is very important (making the load impedance equal to the conjugate of the excitation source internal resistance). In high-frequency circuits, the matching of signal line terminals is more important:On the one hand, ZL=Zc is required to ensure that there is no standing wave along the line; on the other hand, in order to obtain the maximum power, it is required that the input end of the signal line should be conjugate matched when connected to the excitation source. Therefore, matching has a direct impact on the performance of microwave circuits. It can be seen that if the terminals do not match, reflections and standing waves will occur on the signal line, resulting in a drop in load power (high-power standing waves will also cause ignition at the antinode).Due to the existence of reflected waves, it will have adverse effects on the excitation source, resulting in a decrease in the stability of the operating frequency and output power. However, in practice, the given load impedance is not necessarily the same as the characteristic impedance of the signal line, and the impedance of the signal line and the excitation source is not necessarily conjugate, so it is necessary to understand and apply impedance matching technology.(4) PCB layeringHigh-frequency circuits often have high integration and high wiring density. The use of multi-layer boards is not only necessary for wiring, but also an effective means to reduce interference. Reasonable selection of the number of layers can greatly reduce the size of the printed board. It can make full use of the middle layer to set up shielding, which can be better realized. Nearby grounding can effectively reduce parasitic inductance, can effectively shorten the transmission length of signals, can greatly reduce cross-interference between signals, etc. All of these are beneficial to the reliable operation of high-frequency circuits. There are data showing that four-layer boards of the same material are more expensive than The noise of double-sided panels is 20dB lower, but the higher the number of layers, the more complex the manufacturing process and the higher the cost.(5) Power isolation and ground splitCircuit wiring with different functions or different requirements often requires power isolation and ground wire splitting. For example, analog circuits and digital circuits, weak signal circuits and strong signal circuits, sensitive circuits (PLL, low jitter trigger, etc.)Basic requirements: 1. The power layer or ground layer in different areas should be connected together at the power inlet, usually in a tree structure or finger structure. The ground wire division method of different functional circuits, the division gap and the edge of the board should not be less than 2mm. 2. Power zones and ground zones of different types cannot cross each other. 3. Trench and bridge. Due to the division of the ground plane, the signal transmission return loop between the various functional circuits is often discontinuous. In order to ensure the connection of the signal, power supply and ground, in addition to using transformer isolation (can not transmit DC signals), optocoupler isolation ( Difficult to transmit high frequency), the commonly used bridging method. The "bridge" is actually a gap in the trench, and there is only one. When using this method, it is best to connect both sides of the bridge to chassis ground if it is a multi-point grounding system (as all high-speed designs are).SummarizeIn product engineering, PCB design occupies a very important position, especially in high-frequency electrical design. The same principle design, the same components, PCBs made by different people have different results. There are many things that are feasible in principle but difficult to achieve in engineering, or things that others can achieve but others cannot. Therefore, it is not difficult to make a PCB board, but it is not easy to make a good PCB board. things.The above is the high-frequency circuit PCB design technology introduced by Shenzhen Zuchuang Microelectronics Co., Ltd. for you. If you have software and hardware function development needs for smart electronic products, you can rest assured to entrust them to us. We have rich experience in customized development of electronic products, and can evaluate the development cycle and IC price as soon as possible, and can also calculate PCBA quotations. We are a number of chip agents at home and abroad: Songhan, Yingguang, Jieli, Ankai, Quanzhi, realtek, with MCU, voice IC, Bluetooth IC and module, wifi module. We have hardware design and software development capabilities. Covering circuit design, PCB design, single-chip microcomputer development, software custom development, APP custom development, WeChat official account development, voice recognition technology, Bluetooth wifi development, etc. It can also undertake the research and development of smart electronic products, the design of household appliances, the development of beauty equipment, the development of Internet of Things applications, the design of smart home solutions, the development of TWS earphones, the development of Bluetooth earphone speakers, the development of children's toys, and the research and development of electronic education products.
07-02
2023
DFM design for manufacturability of through-hole PCBThis article introduces some DFM methods related to through-hole packaging. These principles are universal in nature, but not necessarily applicable in every situation. However, for PCB designers and engineers dealing with through-hole technology Believe it or not, it helps.1. PCB typesetting and layoutProper layout at the design stage can avoid many troubles in the manufacturing process.(1) Using a large board can save materials, but due to warpage and weight, it will be difficult to transport during production. It needs to be fixed with special fixtures, so try to avoid using boards larger than 23cm×30cm. It is best to control the size of all the boards within two or three types, which helps to shorten the downtime caused by adjusting the guide rails, repositioning the barcode reader, etc. when the product is replaced, and the number of board sizes is ok Reduce the number of wave soldering profiles.(2) It is a good design method to include different kinds of panels in one board, but only those boards that are finally made into one product and have the same production process requirements can be designed in this way.(3) Some borders should be provided around the board, especially when there are components on the edge of the board, most automatic assembly equipment requires at least 5mm of board edge area.(4) Try to wire on the top surface (component surface) of the board, and the bottom surface (soldering surface) of the circuit board is easily damaged. Do not route wiring close to the edge of the board, because the production process is held by the edge of the board, and the wiring on the edge will be damaged by the claws of the wave soldering equipment or the frame conveyor.(5) For devices with higher pin counts (such as terminal blocks or flat cables), oval pads should be used instead of round. To prevent tin bridges during wave soldering.(6) Make the spacing between the positioning holes and the distance between them and the components as large as possible, and standardize and optimize their size according to the insertion equipment: do not electroplate the positioning holes, because the diameter of the plating holes is difficult to control.(7) Try to make the positioning holes also be used as the mounting holes of the PCB in the final product, which can reduce the drilling process during production.(8) The test circuit pattern can be arranged on the waste edge of the board for process control, and the pattern can be used to monitor the surface insulation resistance, cleanliness, solderability, etc. during the manufacturing process.(9) For larger boards, a path should be left in the center to support the circuit board at the center during wave soldering, to prevent the board from sagging and solder sputtering, and to help the board surface to be welded consistently.(10) The testability of the bed of needles should be considered in the typesetting design. Plane pads (without leads) can be used for better connection with pins during online testing, so that all circuit nodes can be tested.2.The positioning and placement of circuit board components(1) Arrange components in rows and columns according to a grid pattern position, and all axial components should be parallel to each other, so that the axial insertion machine does not need to rotate the PCB during insertion. Unnecessary turning and movement can significantly slow down the inserter.(2) Similar components should be arranged in the same way on the board. For example, make the negative poles of all radial capacitors face the right side of the board, make the missing El marks of all dual in-line packages (DIP) face the same direction, etc., which can speed up the insertion speed and make it easier to find errors.(3) The arrangement direction of dual-in-line packaged devices, connectors and other multi-pin components is perpendicular to the direction of wave soldering, which can reduce the tin bridge between component pins.(4) Make full use of silk screen to mark the board surface, for example, draw a frame for barcode, print an arrow to indicate the direction of the board through wave soldering, and use a dotted line to trace the outline of the bottom surface components (so that the board only needs to be silk screened once) )etc.(5) Draw the component reference designation (CRD) and polarity indication, and it is still visible after the component is inserted, which is very helpful in inspection and troubleshooting, and is also a good maintenance job.(6) The distance between the components and the edge of the board should be at least 15mm (preferably 3mm), which will make the circuit board easier to transfer and wave solder, and will cause less damage to peripheral components.(7) When the distance between the component and the board needs to exceed 2mm (such as light-emitting diodes, high-power resistors, etc.), gaskets should be added below it. Without spacers, these elements would be "squashed" during transport and would be susceptible to vibration and shock in use.(8) Avoid placing components on both sides of the PCB, because this will greatly increase the labor and time of assembly. If the component must be placed on the bottom surface. It should be physically close as possible so that the masking and stripping of the solder mask tape can be completed at one time.(9) Try to distribute the components evenly on the PCB to reduce warpage and help to distribute heat evenly during wave soldering.3. Circuit board machine insertion(1) The pads of all board components should be standard and industry standard spacing should be used.(2) The selected components should be suitable for machine insertion. Keep in mind the conditions and specifications of the equipment in your own factory, and consider the packaging form of the components in advance so that they can better cooperate with the machine. Packaging can be a bigger issue for odd-shaped components.(3) If possible, the axial type of the radial element should be used as much as possible, because the insertion cost of the axial element is relatively low. If the space is very precious, the radial element can also be preferred.(4) If there are only a small number of axial elements on the board, all of them should be converted to radial type, and vice versa, so that an insertion process can be completely saved.(5) When laying out the board surface, the direction of pin bending and the reach of the components of the automatic insertion machine should be considered from the perspective of the minimum electrical spacing, and at the same time, it should be ensured that the direction of pin bending will not cause tin bridges.4. Wires and connectors(1) Do not connect wires or cables directly to the PCB, but use connectors. If the wire must be soldered directly to the board, the end of the wire should be terminated with a wire to a terminal on the board. The wires coming out of the circuit board should be concentrated in a certain area of the board so that they can be nested together to avoid affecting other components.(2) Use wires of different colors to prevent errors during assembly. Each company can adopt its own set of color schemes, for example, the high position of all product data lines is represented by blue, while the low position is represented by yellow, etc.(3) The connector should have larger pads to provide a better mechanical connection, and the leads of high-pin-count connectors should have chamfers for easier insertion.(4) Avoid using dual in-line package sockets. In addition to prolonging assembly time, this additional mechanical connection reduces long-term reliability, and sockets should only be used when DIP field replacement is required for maintenance reasons. The quality of DlP has made great progress nowadays, and it does not need to be replaced frequently.(5) Marks to identify the direction should be engraved on the board to prevent mistakes when installing the connector. The solder joints of the connectors are places where mechanical stress is more concentrated, so it is recommended to use some gripping tools, such as keys and snaps.5.The whole system(1) Components should be selected before designing the printed circuit board, which can achieve the best layout and help implement the DFM principles described in this article.(2) Avoid using parts that require machine pressure, such as wire pins, rivets, etc. In addition to being slow to install, these parts may also damage the circuit board, and they are also poor in maintainability. (3) Use the following method to minimize the types of components used on the board: replace a single resistor with a row resistor: replace two three-pin connectors with a six-pin connector. The values of the two components are very similar, but If the tolerances are different, use the one with the lower tolerance for both locations: use the same screws to hold the various heatsinks on the board. (4) It is best designed as a universal board that can be configured on site. Such as installing a switch to change a board for domestic use to an export model, or using a jumper to change one model to another.6. Conventional requirements for PCB board design(1) When conformal coating is applied to circuit boards, the parts that do not require coating should be marked on the drawing during engineering design. The influence of the coating on the line-to-line capacitance should be considered in the design.(2) For through holes, in order to ensure the best welding effect, the gap between the pin and the aperture should be between 0.25mm and 0.7Omm. A larger aperture is beneficial for machine insertion, but a smaller aperture is required to obtain a good capillary effect, so a balance needs to be struck between the two.(3) Components that have been pretreated according to industry standards should be selected. Component preparation is one of the least efficient parts of the production process, and in addition to adding an extra step (with a corresponding risk of electrostatic damage and longer lead times), it also increases the chance for error.(4) Specifications should be determined for most of the manual plug-in components purchased, so that the length of the lead wires on the soldering surface of the circuit board does not exceed 1.5mm. This reduces component preparation and lead trimming effort, and the board passes wave soldering equipment better. (5) Avoid using snap fits for smaller mounts and radiators, as this is slow and requires tools. Sleeves, plastic quick-connect rivets, double-sided tape, or mechanical connections using solder joints should be used whenever possible.SummarizeFor manufacturers of board assemblies using through-hole technology, the DFM is an extremely useful tool that saves a lot of money and hassle. The benefits of using DFM methods to reduce engineering changes and make future design compromises are very immediate.The above are the details of DFM design for manufacturability of through-hole PCB introduced by Shenzhen Zuchuang Microelectronics Co., Ltd. If you have software and hardware function development needs for smart electronic products, you can rest assured to entrust them to us. We have rich experience in customized development of electronic products, and can evaluate the development cycle and IC price as soon as possible, and can also calculate PCBA quotations. 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