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TPS65130: Noise on negative output

Darren Jenkins
Genius 12801 points
Part Number: TPS65130


TPS65130 team,

We have an audio customer seeing noise in the audio band on the negative output of the TPS65130.  They a slight increase in the noise at around 2 to 3 kHz before the noise drops off at higher frequencies.

Adding a capacitance on the negative output increases the hump at 2 to 3 kHz.  Reducing capacitance will increase the noise broadly at lower frequencies.

They have a 4.7nF cap on CN, as recommended. Can this cap be adjusted to help with this?  Does it make sense to add a series resistor here to change the compensation network?

I think a series resistor is being recommended here:

https://e2e.ti.com/support/power-management/f/power-management-forum/66338/tps65130-design-spreadsheet/240038

Any advice on what to try?

Thanks,

Darren

  • 0
    TI__Mastermind 18550 points

    Hello Darren,

    Network on CN pin mostly impacts transient response and I would not expect it impact low frequency noise much. Is the device operating in PWM or PFM mode? It is possible that noise is because of device operating in bursty PFM mode and for audio applications, I would suggest to tie PSP/PSN pins to GND to have constantly high frequency PWM operation. If PSP/PSN are not tied to GND, please try this first. Another thing to try is to remove the feedforward capacitor in the feedback resistor divider path as noise can couple into FBN pin through this path. Hopefully, these suggestions can reduce the noise enough for this application.

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    TI__Genius 12801 points

    Hi Liaqat,

    The customer already has PSP and PSN tied to ground. 

    Regarding the feedforward caps, the negative side has 13pF in series with a 10kOhm.  The positive side has 15pF in series with a 10kOhm.  I'll recommend removing them.

    Thanks,

    Darren

  • 0 in reply to Darren Jenkins
    TI__Mastermind 18550 points

    Yes, if PSP/PSN are GND, I would try breaking feedforward path next.

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    TI__Genius 12801 points

    Hi Liaqat,

    Removing the feedforward path did not help.

    The noise goes away when the load current is increased from about 35 mA to about 52 mA.  Can this be fixed through the compensation network?  Is there something else that can be done?

    Adding more capacitance on the load increases the noise at 3kHz.

    Thanks,
    Darren

  • 0 in reply to Darren Jenkins
    TI__Mastermind 18550 points

    Hi Darren,

    Since you sent me more information via e-mail and we are discussing this topic on that e-mail thread, I will close this thread here.

    Kind Regards,

    Liaqat