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TPS65132: Ripple of VNEG of TPS65132 is too big

Part Number: TPS65132

Dear all,

Here we use TPS65132A to supply LCD screen of a tablet, the AC ripple of VNEG seems to reach 700mV, too large. While I use pin2pin solution-NT50358. The ripple is much smaller. I don't think it's normal. Look forward to your reply.

(1)DC of AVEE of TPS65132A:

(2)AC of AVEE of TPS65132A:

(3)AC of AVEE of NT50358:

  • Hi Jiayu,

    Yes, 700mv of ripple for VNEG rail is excessive. Normally this ripple should be less than 50mv. What is the load on VNEG in this application? It is possible that  higher ripple is due to excessive current draw from this rail. This device is factory programmed for 40mA current on this rail by default which can be changed to 80mA by setting the APPS bit (bit 6 in register 0x03). Can you please also share the schematics so that I can ensure that there are no issues.

    Kind Regards,

    Liaqat

  • Hi Liaqat,

    Thanks a lot for your quick response.

    (1) The load is real LCD panel in this application.

    (2) Actually, we have set the APPS bit to "1" to increase the current capability of neg rail to 80mA. I am not sure whether it is enough.I want to apply for 65132S sample to do comparison test, but found they were not pin2pin(-A with -S)

    (3) Of course I can ask customer to send you schematic to double check. Update later.

  • Hi Jiayu,

    Thank you for the response. If the load is LCD panel, please do still measure the current on this rail. Once I get the schematics, I will review to see if I can spot anything that can cause higher ripple.

    Kind Regards,

    Liaqat

  • Hi Jiayu,

    Since you sent the schematics via private e-mail, I will respond to your e-mail and am closing this thread.

    Kind Regards,

    Liaqat

  • Hi Liaqat,

    Okay, thanks, wait for you.