Digital & Analog Circuit Design Requirement is critical important in the process of PCB Design, The circuit board should be divided into four types of circuits (RF analog signals, interface circuits, common digital circuits, -48V, power supply and other high-power wiring areas) to reduce mutual interference between various types of circuits and improve resistance to interference outside the equipment and reduce external emissions.
Ordinary digital circuit area should also pay attention to high-speed digital circuits (ultra-high-speed differential, single-ended clock lines above 10MHz, edge-sensitive signals such as reset lines), should be as far away as possible from other areas.
Since the digital circuit has strong interference to the analog circuit through the plane, as a result of that, PCB partition will help to separate an independent analog part and a digital part. Appropriate component layout should consider the direction of signal flow, weak signal, strong signal, digital signal should be arranged in order.
Generally speaking, the layout of ultra-high-speed differential circuit should try to ensure the same data transmission direction of adjacent signals, and the data transmission direction is different. Isolation between channels should be considered one level higher than other in the same direction.
The source string resistance should be placed as close as possible to the driver device. The terminal device should be placed close to the receiver device as close as possible to the nearest limit of the process. When the layout resources are limited, the 10MHz single-ended clock must be Priority.
Decoupling capacitors should be placed as close as possible to the power pins of the chip.
Lightning surge protection devices should be placed as close as possible to the connector to which they are attached.
The protection circuit for the chip in the circuit board should be as close as possible to the position of the protected chip. The primary protection circuit such as the gas discharge tube and the varistor should be as close as possible to the source port of the surge voltage
