LMR14030: lmr14030 low frequency noise issue

Mason Liu

Part Number: LMR14030

Hi,

Recently I built a BUCK(from 24v to 12v) using LMR14030 with the schematic as below, but it doesn’t work well. We observe some very low freq noise in Vin, could you give us some suggestions?

Thanks.

Mason

over 4 years ago

0 iAlejandro over 4 years ago

TI__Expert 8130 points

Hello Mason,

Input ripple can be reduced by either boosting the capacitance or reducing the ESR of Cin. I noticed a ceramic cap is used at Cin, which typically has a very low ESR and add little to the input voltage ripple.

I would recommend to increase Cin. Have you tried increasing the input capacitance?

Also, let's make sure we are measuring it properly. Improper measurement techniques can result in exaggerated noise. How are you probing the scope-probes? Clip-on method? Please take a look at the following:

How to measure ripple for better design outcomes

Testing switching power supplies includes many different tests, one of them being the output-voltage peak-to-peak ripple. Output-voltage ripple is the alternating current (AC) component of the direct current…

By George Lakkas over 9 years ago in Technical articles > Power management