Hi everyone, I'm Goat-kun.
When designing hardware PCB circuits, layout is the top priority, and a good layout can bring stable performance to the circuit board and greatly facilitate the wiring. There are some important points to follow when it comes to layout. The following 18 points need to be considered accordingly when layout, and you can refer to the layout when designing, and collect them.
(10) Analog, digital, power supply, and protection circuits should be separated
This is the basic of the basics, especially the analog signal circuit and the digital signal circuit, which definitely need to be laid out separately
(11) The interface protection device should be placed as close to the interface as possible
The interface protection device protects the interface, so it should be placed close to the interface, which should be well understood.
(12) Requirements for the placement sequence of interface protection devices
The placement of the protection devices is also particular in the layout.
For power lightning protection devices, the general order of placement is varistors, fuses, suppression diodes, EMI filters, inductors, etc., first one and then the next. If there is no device on the schematic, it can be laid out in the order above.
For the protection devices of interface signals, the order is ESD (TVS tube), isolation transformer, common mode inductance, capacitor, and resistor, which need to be laid out in strict order, if there is no device on the schematic, it can also be laid out in the above order. As shown in the figure below, it is a standard layout.
(13) Devices that are susceptible to ESD interference
For this type of device, electronic devices such as NMOS and CMOS are common, and the layout needs to be as far away as possible from areas that are prone to ESD interference, such as the edge part of the board.
(14) Clock device layout
Clock devices, that is, crystal oscillators, crystal and clock distributors, etc., need to be close to the IC devices when layout, so that the transmission distance will not be too long. It is also necessary to pay attention to the fact that the clock device should not be placed close to the high-power and heat-dissipating device to avoid interference, and the filter of the clock circuit also needs to be placed closer to the power input pin of the clock circuit.
At the same time, it is also necessary to consider whether a 22 ohm resistor needs to be connected in series to the output of the clock splitter according to the actual circuit design, and whether the output that is not used by the clock splitter should be connected to GND through the resistor.
(15) Circuit layout of switching power supply module
The layout of the switching power supply needs to be compact, not too scattered, the input \ output circuit should be separated, the corresponding layout should be carried out according to the requirements of the schematic diagram, and the placement of the capacitor should be reasonable to achieve the ideal filtering effect.
(16) The relative position of the switching power supply
It is necessary to pay attention to the placement of the switching power supply, and the switching power supply circuit part should be kept away from the AD\DA converter, sensitive devices, clock devices and analog devices during the layout, otherwise it will interfere with the situation.
(17) Capacitors and filter devices
The placement of capacitors is a common operation during layout, and it needs to be placed close to the pins during layout, and the smaller the capacitance, the closer the capacitor is to the power pins.
The EMI filter needs to be close to the input port of the chip power supply so that the chip input is a stable input.
(18) The arrangement of components is convenient for debugging and maintenance
This is combined with the actual scene, for the components that need to be debugged in the later stage, there needs to be enough space around to prevent accidental damage to the components next to them during debugging or maintenance.