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TPS54202: Vibration noise on inductor

Part Number: TPS54202

Hello,

We are designing TPS54202DDCR from 24V to 5V application.

the schematic is as below, I found that there is a vibration noise in L1 inductor when the load current is over 400~500mA, but it is okay with less load current, about 100~150mA.

also I changed value of the passive components as below, the noise was same.

(i changed L1 to 22uH, it was same.)

in addition, I found some information in datasheet, about pulse skip mode (eco-mode) that activates under 300mA load current.

is there any relevance between vibration noise and pulse skip mode?

Or Should I change some values of my components to get rid of vibration noise?

Please review this schematics for solve this problem. Thanks.

Chase Jeong

  • Hi Chase,

    I can't see the schematic , could you help attach them again ? thanks .

    The devices are designed to operate in high-efficiency pulse-skipping mode under light load conditions. Pulse skipping initiates when the switch current falls to 0 A/ the peak inductor current is lower than 300 mA typically. During pulse skipping, the low-side FET turns off when the switch current falls to 0 A. The switching node (the SW pin) waveform takes on the characteristics of discontinuous conduction mode (DCM) operation and the apparent switching frequency decreases. As the output current decreases, the perceived time between switching pulses increases.

    The audible noise occurs from inductor or capacitor when frequency < 20KHz at light loading. And this is common . You can try the distributed airgap inductors.  Also you can RTV the coil or varnish.

    Could you confirm the frequency of SW when Vibration noise ?

    BRs,

    Young

  • Hi Young,

    here is the first schematic.

    and this is second schematic.

    i changed the value of L1 to 22uH from this values.

    please check it. Thanks.

  • Hi, Jeong 

    Most time, the audio noise is generated by MLCC, not by inductor, there is an application note for your reference. 

    In order to eliminate the audio noise completely, suggest changing the Cout(C15 and C17) to Ecap with small ESR, then test again. 

     

  • Hi Zhao,

    Thank you for your reply, i will try your solution, and tell you the result asap. Thanks.