General rules for PCB design and wiring

When designing PCB, pay attention to the following points:
(1) From the perspective of reducing radiation disturbance, multi-layer boards shall be selected as far as possible, and the inner layer shall be used as power supply layer and ground wire layer respectively, so as to reduce the impedance of power supply line, suppress the public impedance noise, form a uniform ground plane for signal line, increase the distributed capacitance between signal line and ground plane, and restrain its ability to radiate into space.
(2) The power line, ground wire and PCB wiring shall maintain low impedance to high-frequency signals. When the frequency is very high, the power line, ground line or PCB wiring will become a small antenna for receiving and transmitting disturbance. In addition to adding filter capacitor, the method to reduce this disturbance is to reduce the high-frequency impedance of power line, ground wire and other PCB routing itself. Therefore, the routing of various PCBs should be short and thick, and the lines should be uniform.
(3) The power line, ground wire and printed wire shall be properly arranged on the PCB, and shall be short and straight as far as possible, so as to reduce the loop area formed between the signal line and the return line.
(4) The clock generator shall be as close as possible to the device using the clock.
(5) The shell of quartz crystal oscillator shall be grounded.
(6) Circle the clock area with ground wire, and the clock line shall be as short as possible.
(7) PCB shall use 45 ° broken line instead of 90 ° broken line wiring as far as possible to reduce the external transmission and coupling of high-frequency signals.
(8) Single point power supply and single point grounding for single panel and double-sided panel; The power line and ground wire shall be as thick as possible.
(9) The I / O drive circuit shall be as close as possible to the connector on the side of the PCB to leave the PCB as soon as possible.
(10) The key lines shall be as thick as possible, and protective areas shall be added on both sides. High speed lines should be short and straight.
(11) The component pin shall be as short as possible, and the decoupling capacitor pin shall be as short as possible. It is best to use the patch capacitor without lead.
(12) For a / D devices, the ground wires of digital part and analog part should be unified rather than crossed.
(13) Clock, bus and chip selection signals shall be far away from I / O lines and connectors.
(14) Analog voltage input line and reference voltage terminal shall be far away from digital circuit signal line as far as possible, especially clock.
15) The clock line perpendicular to the I / O line has less interference than the parallel I / O line, and the clock element pin should be far away from the I / O cable.
(16) Do not route wires under quartz crystals and noise sensitive devices.
(17) Do not form current loop around weak signal circuit and low-frequency circuit.
(18) Do not form a loop for any signal. If it is inevitable, keep the loop area as small as possible.

Commax-Tech Electronic Co., Ltd      Electronic component specialist

B23, second floor, ASEAN building, Longhua District, Shenzhen

sales@commax-tech.com

https://commax-tech.com

Keyword：PCB Design   General Wiring Rules   I/O Drive Circuit   A/D Device   Clock   Bus   Chip Select Signal   Analog Voltage Input Line   Reference Voltage Terminal   Clock Element   Quartz Crystal   Current Loop   Commax-Tech Electronic