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TPS51200 malfunctioning

Basil Alias
Prodigy 90 points
Other Parts Discussed in Thread: TPS51200

We are using TPS51200 in a board for DDR2 termination power. We are expecting a voltage of 0.9V at the Vout (VTT) rail and REF_OUT rail. But we are getting 0.3V only. Also after enabling the LDO, It is getting heated up very much. Powergood is Low. We are stuck at this issue... What could be the reason for this? Any suggestions?. The figure below Indicates the schematic Portion which contains LDO

  • 0
    TI__Mastermind 49370 points

    Hi Basil,

    The schematic looks good. I am wondering if the issue is from the PCB layout. Here are my suggestions: 1. Check the PCB layout to see if three output caps(C272, C273 and C274) for Vo are close to pin3. These three caps should be placed close to pin3 with short and wide connection in order to avoid additional ESR/OR ESL trace inductance. Otherwise you may get oscillation and IC gets hot.  2. Check the bypass caps for VLDOIN(C495 and C348) if they are close to pin2.  3. Check the bypass cap for Vin(C347) if it is close to pin10. 4. If all above three items are close to their pins, you cam measure the voltage on pin1, it should be 0.9V. if it is not 0.9V, you should check VCC_1V8 if it is correct. Hope these will help.

    Thanks,

    Nancy

  • 0 in reply to Nancy Zhang
    Prodigy 90 points

    Thank you Nancy for the reply. I have changed the capacitor at Vo rail to Ceramic  10uF(which is having low ESR values), now we are getting correct output and oscillation also gone.