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TPS53353: TPS53353 can't output Power

Max Chang1
Prodigy 10 points
Part Number: TPS53353

Hi Sir
We use TPS53353 5V 8A output design, system power up can't output 5V, we checked Enable, VREG, VDD, VIN voltage is OK,
but we remove C115, the TPS53353 can output 5V(please see the attachment)

Can you tell the us reason? 

Is Rr and Cr value effect?(R227,C112,C115)

If yes, please recommend value to us

BRs

Max

  • 0
    TI__Guru**** 191445 points

    Max,

    TPS53353 uses DCAP control mode with hysteretic off time.  This control type requires some ripple voltage component at the VFB pin.  Typically that ripple component is supplied by the inductor ac ripple current and the ESR of electrolytic output capacitors.  For all ceramic output capacitors, there is not enough ESR to supply the needed ripple voltage, so an external ripple injection circuit ( R227,C112,C115) is used.  In your case, you are mixing ceramic and electrolytic, however the ceramic portion is relatively small compared to the electrolytic capacitors.  an external ripple injection circuit may not be required. It would depend on the amount of ESR of C73 and C91.   Can you provide the waveform of the VFB voltage along with the  LL (switch node) voltage?

  • 0 in reply to JohnTucker
    TI__Guru**** 191445 points

    Max,

    Any update?  I will close this thread for now.  You can reopen it if you need further assistance.