Views:13 Author:Site Editor Publish Time: 2020-07-27 Origin:Site
Precautions for PCBA control board component layout
1. In the PCB layout of components, related components should be placed as close as possible. For example, clock generators, crystal oscillators and CPU clock input terminals are prone to noise. When placed, they should be placed close to each other. For those devices that are prone to noise, low-current circuits, high-current circuit switching circuits, etc., keep them away from the microcontroller logic control circuit and storage circuit (ROM, RAM) as much as possible. If possible, these circuits can be made into circuit boards, which is beneficial Anti-interference, improve the reliability of circuit work.
2. Try to install decoupling capacitors next to key components such as ROM and RAM chips. In fact, PCB routing, pin routing and routing may contain large inductive effects. Large inductance may cause severe switching noise spikes in the Vcc wiring. The only way to prevent switching noise spikes in the Vcc wiring is to place a 0.1uF electronic decoupling capacitor between Vcc and the source. If a surface mount component is used on the circuit board, the chip capacitor can be placed directly against the component and connected to the Vcc pin. It is best to use ceramic tile capacitors because of their low ESL electrostatic loss, high frequency impedance, and good dielectric stability over temperature and time. Since tantalum capacitors have high impedance at high frequencies, tantalum capacitors should not be used as much as possible.
Pay attention to the following points when placing decoupling capacitors on PCBA control board PCB design:
1. The power input terminal of the printed circuit board is connected to an electrolytic capacitor of about 100uF. If the volume allows, larger capacity will be better.
2. In principle, a 0.01uF ceramic capacitor should be placed next to each IC chip. If the gap of the circuit board replica is too small to be placed, 1-10 tantalum capacitors can be placed for every 10 chips.
3. A decoupling capacitor should be connected between the power line (Vcc) and the ground line to deal with components with weak anti-interference ability and large current changes during shutdown, as well as storage elements such as RAM and ROM.
4. The capacitor lead should not be too long, especially for high-frequency bypass capacitors.