LV2862: Optimizing buck converting efficiency and audible ringing for low load application

Hi Yixing,

• The device will switch at a lower frequency during light load i.e. ECO mode (or PFM mode for other dc dc converters). In case it is within the audible band, it can cause audible hissing sound. Could you please measure the switching frequency by probing the SW pin? We can confirm this after you share the requested waveform. Also, please share the inductor DS. 
• You can try using a powdered iron inductor. Relative to a ferrite-cored inductor with discrete airgap, this can improve the issue.
• The noise could also be due to the piezoelectric effect of the ceramic input and output caps https://e2e.ti.com/blogs_/b/powerhouse/posts/how-to-reduce-acoustic-noise-of-mlccs-in-power-applications Could you please measure the voltage ripple at the input and output caps? In case the ripple is high, you may want to try adding some more caps.
• Note that it is recommended to use ceramic capacitor of 2.2 µF–10 µF value with X5R or X7R dielectric as input capacitance.
• You may want to look into LMR516xxSIMPLE SWITCHERPower Converter, 4-V to 65-V, 0.6-A/1-A Buck Converter in a SOT-23 Package datasheet (Rev. B) for your application.

Regards

Arpita

Hi Arpita,

Here are the waveforms of the SW pin.

Zoomed in Below:

Zoomed out below:

I checked the VIN and VOUT ripple. The VIN ripple is 130mV pkpk and the VOUT ripple is 72mV pkpk.

I'll take a look at the LMR51603.

Thanks!

Hi Yixing,

Looks like it can be due to inductor as the pulse skip frequency is ~15Khz. To confirm this, could you please run it for higher load (CCM) and check if the audible noise goes away. Also please try changing the inductor and check if the audible noise goea away.