LP8556: Audible noise and unstable VLDO output

Part Number:LP8556

Hi,

We are having audible noise issue from a recently build. Previous builds do not have this issue and the design did not change.

Two differences we found when comparing the current (audible noise) and previous (no audible noise) builds are:

1. The VLDO output on the current build has frequency components in the audible range. See the scope capture below.

2. The VLDO ripple on the current build is much larger (~500mV) comparing to previous build (<20mV).

Any insights for debugging this?

Thanks,

Peter