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TPS562210A: Bad audible noise probably generated by inductor

Piocky
Intellectual 310 points
Part Number: TPS562210A
Other Parts Discussed in Thread: TPS562219A

Hi,

I'm using the TPS562210A in a project to generate 5V from 12V (also tried 15V, the result is the same), which is used to power a Raspberry Pi 3 model A+.

The system is working, but Ive got a very annoying noise coming from the power management stage, and I think that I found the source of this noise, which must probably be the inductor. This is the waveform on SW: 

The problem is that I don't know what is causing this issue, as I followed the guidances from the datasheet and the EVM User Guide. Any advice on this will be more than helpfull!

Attached are the schematic and the layout of the circuit.

Thanks for reading me,

Yoann

  • 0
    TI__Genius 9550 points

    hi Yoann,

    Checked the schematic and it is ok for me.

    Need more information to analysis:
    1. Loading is stable or dynamic? if it is a stable loading, what value?

    2. plot Vin, Vou(AC, check ripple)

    3. try to use TPS562219A, check if the issue disappear

     

  • 0 in reply to Jason Wang (BSR-MV)
    Intellectual 310 points

    Hi Jason,

    First of all, thanks a lot for your quick response!

    1. I'd say that the load is dynamic, as the 5V is used to power a Raspberry Pi, with a current consumption depending on the use of the processor, and the other modules. (NB: the Raspberry generates 3.3V from 5V, which is used by others modules)

    2. Here are the two plots you asked for (Vin first, and Vout)

    3. I asked the question to a friend of mine who is working as FAE at TI Paris, and he told me that the noise is more probably coming from the ceramic capacitor C25, and caused by the fact that the circuit is switching in light load. So according to the datasheet, I think that refers to the Eco mode. I will try to use the TPS562219A instead as you proposed, to stay in PWM mode all the time.

    I will let you know with my progress when I'll receive it. Thanks again for your help.

    Yoann

  • 0 in reply to Jason Wang (BSR-MV)
    Intellectual 310 points

    Hi Jason,

    I received the TPS562219A last week and soldered it on my PCB, and it did fix my issue, I don't have that bad noise anymore, so thanks a lot!

    You think the problem was that i wasn't seeking enough current from it? So it was constantly going to eco-mode?

    Best regards,

    Yoann

  • 0 in reply to Piocky
    TI__Genius 10070 points

    Hi,

    Because the load changes, so the switching frequency is lower when the converter enters Eco-mode, when the frequency is below 20KHz, or the difference frequency interference is caused by the audio IC working frequency and TPS562210A switching frequency.

    From the layout, we don't recommend put the SW trace under IC, the switching noise is easy to be introduced to FB pin, this may lead to the unstable.

    Shawn

  • 0 in reply to Shawn Nie
    Intellectual 310 points

    Ho Shawn,

    Thanks for the precision, I did change the position of the SW trace following the PCB layout recommendation, but didn't try the new layout with TPS562210A, just with TPS562219A, so can't say if it was the only problem. I'm just happy of not hearing this noise anymore!

    Have a good day,

    Yoann