Hello,
My customer encounted humming noise isse on the AM335x and TPS65218D0 board they designed.
They tried enabling forced PWM but the symptom was the same.
Please advise on the cause of the issue and how to fix it.
Here is the customer's schematic and layout.
Thank you.
JH
Hi JH,
Thank you for your patience and providing the layout and schematic. Audible noise is often generated by the inductors and capacitors of a BUCK output. Can you please have your customer provide the part number of the 10 uH inductor they are using for the inductors marked L8 and L9 in the schematic?
Enabling force PWM mode should cause the switching frequency to no longer be in the audible range. How is the customer enabling force PWM and are they able to confirm the register is actually being set correctly?
For example, the registers to enable force PWM are password protected, if the steps to write a password protected register are not followed the setting will not change. This could explain why symptoms are the same after attempting to enable force PWM.
I have also linked a blog post on noise generated from MLCC's (multilayer ceramic capacitors) for reference. https://e2e.ti.com/blogs_/b/powerhouse/posts/how-to-reduce-acoustic-noise-of-mlccs-in-power-applications
Regards,
Garrett
