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TPS65131: Problem for Vout ripple variation

Satoshi
Guru 19485 points
Part Number: TPS65131
Other Parts Discussed in Thread: TPS65130, TPS54531

One customer was develop TPS65131+α board.

When these board evaluated, TPS65131 Vout ripple were large variated.

Please see test results below, Vout ripple become 72.9mV to 887mV depend on the board.

(The same circuit, layout, and condition)

・Example Vout ripple waveform on large Vout ripple board (200mV/div and 500μs/div scale)

・Example Vout ripple waveform on normal Vout ripple board (20mV/div and 50μs/div scale)

【Question】

Please let me know about four points below;

・I think that the reason is variation of TPS65131's control circuit and external components, correct?

・If correct, is there improve point of reduce variation on external components?

・I found below E2E thread for TPS65130, is TPS65131 also possibility for depend on marking?

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/952655/tps65130-tps65130-vpos-ripple-issue-in-power-save-mode/3522644

・If there the other reason, please let me know.

【Additional Information】

・TPS65131's spec: 5Vin to ±15V, less than 100mA

　External components is, L: 4.7μH, Cout: 10μF ×3, the other parts are based on datasheet recommendation. 

・When increase Iout, Vout ripple was decreased. but deference between board ripple are staying.

・5Vin side is supplied from TPS54531's 5Vout, and these ripple are depend on board, too.

　But TPS54531 have not reason because when TPS54531 and TPS65131 cutoff and evaluate separately, TPS54531 was not occur large Vout ripple.

If need more detailed information, please communicate on direct e-mail.　

Best regards,

Satoshi

  • +1
    TI__Mastermind 18550 points

    Hello Satoshi,

    Unfortunately, ripple can vary quite a bit from device to device in PFM (power save) mode where switching occurs in bursts as opposed to continuous switching in PWM mode (PSP/PSN pins tied to GND). I am not sure if it is feasible in your application but, if output voltage ripple is an important consideration in target application, I would suggest to tie PSP/PSN pins to GND so that device always operates in PWM mode and provide a consistently lower level of output voltage ripple.

    Kind Regards,

    Liaqat

  • +1 in reply to Liaqat Khan
    TI__Mastermind 18550 points

    Hello Satoshi,

    Since you sent me schematics using private message and discussing this on private thread, I will close this thread.

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    Guru 19485 points

    Hi Liaqat

    Thank you for your advice on private massage.

    I will close and resolved this thread.

    Best regards,

    Satoshi