Decoupling capacitance design

In general, the design of printed circuit boards is usually in the key part of the board to set decoupling capacitors. Decoupling capacitance is determined by the speed and working frequency of the centralized circuit. In general, the faster the speed, the higher the frequency, the smaller the capacitance required. The following are the design requirements for decoupling capacitors.

1) an electrolytic capacitance of 10 ~ 100 μ F is required for the power supply to be transferred to the human end, and a 10 μ F electrolytic capacitor can also be used to supply a 10 μ F electrolysis.

2)Capacitance-only 0.1 μ F ceramic chip capacitor is connected in parallel to the input end of the power supply. A set of capacitors should be added when the length of the power cord in the printed circuit board is greater than 10 m.

A 1 ~ 10pF capacitor must be connected to the power supply of at least every 4 ~ 8 integrated chips on the board. If the PCB space allows, it is best to connect a 0. 01pf ceramic chip capacitor to the power supply of each integrated chip. The forward capacitance here is to be added between the power line and the ground wire.

3)Good for devices such as RAM ROM memory with less noise resistance when the power supply is disconnected "should be connected between the power supply of the chip and the ground to connect the decoupling capacitor RC circuit to prevent the discharge of the circuit."

4) if there are relays, buttons and other components in the board, the circuit must be populated

It is easy to be interfered by the outside world. When using, the input terminal should be 5) the input impedance of the COMS chip is relatively high, and the grounding or power connection processing is carried out correctly.