Choosing the right bypass capacitor for high-speed circuit design

nathanzhang

Choosing the right bypass capacitor for high-speed circuit design [Copy link]

Attached is Micron's technical document "Selecting the Right Bypass Capacitor for High-Speed Circuit Designs".

Highlights:

1. Two methods for calculating the capacitance of bypass capacitors are introduced;

Method 1:

-The size of the load that a single IC output needs to drive and the voltage slew rate can be used to determine the required drive current.

- Consider the worst case, where all IC outputs drive the same load at the same time. The total driving current required is the current calculated in the previous step multiplied by the number of output ports.

- Given the IC power supply voltage ripple spec and total drive current, the required total bypass capacitor capacity can be calculated;

Method 2:

- Calculate the maximum permissible impedance;

- Use the inflection point frequency (this point has not been seen in previous papers) to calculate the maximum allowable inductance;

- Using the ESL of the selected capacitor and the maximum allowable inductance calculated above, find the number of capacitors required;

2. It is pointed out that the smaller the ESR, the better. In a special case, a small ESR may cause a bigger problem (please look for the details in the document).

freebsder

Thanks for sharing!

nathanzhang

No thanks