0
\$\begingroup\$

At both the input and output (especially the output), I need to place several bypass capacitors (all MLCC). The datasheet for the voltage regulator seems to suggest that using a 10uF on both the input and output is usually adequate. However, I see some high frequency noise (switching regulator) that I'd like to supress as well. To address this, the app note suggests using additional smaller value capacitors targeting those frequencies (based on the resonant frequency of the MLCC capacitor).

I'm using multiple capacitors at varying values, such as 0.001uF, 0.1 uF, 10 uF. Where should I place these three capacitors in relation to the voltage regulator chip?

Should I place the biggest capacitor nearest to the IC or the smallest?

\$\endgroup\$
2
\$\begingroup\$

The smallest value capacitor is placed closest to the IC, within 1/4" (7mm) if possible. The larger value capacitors are next to them as space allows. The output of switching regulators can be smoothed out by combining capacitors with a series inductor of 10uH to 100uH, rated for twice the value of the maximum current flowing.

You will find that combining inductors and capacitors can really smooth out ripple and noise spikes to just a few millivolts. Large value capacitors over 100uF have poor ESR ratings, but they must be present on the power feeds to filter power surges and low frequency ripple. These can be located at power branches or distribution points, often the same place where grounds branch out to individual loads.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.