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TPS62130: Will not go into power save mode with 20-100uA load

Tito Sanchez
Prodigy 10 points
Part Number: TPS62130

I am having an issue with the switching regulator not going power save mode.  My input is 12v and my load is normally around 20uA, but will go up to around 2.5-3.0 amps when my transmitter turns on.  When my load is drawing about 20uA my 12v power supply is at about 350uA.  I do have the evaluation board and measured 30uA on the input when my load is at about 20uA.  I am not sure what is causing my board to draw so much more current. 

I used the same value parts as the EVM board- L1=1uH,C6 =68uF,C1=10uF,C3=22uF, etc.  I tried to follow the same pcb layout but due to size restrictions I had to make the ground plane smaller on all the layers.  Also, I only have 1 internal ground plane.  Another difference is I used ground vias through all the ground planes.  Is it possible the layout could cause this, or do i have some component that is incorrect or bad?

The other thing I have noticed is the ripple frequency on the vout(3.3v) line on the EVM is about 156 Hz with a 20uA load.  On my pcb it is about 1.3kHz with a 20uA load.  In both cases the peak to peak voltage on the ripple is about 40mvpp.

Any suggestions how to troubleshoot this?  

Thanks,

Tj

  • +1
    TI__Expert 7860 points

    Hello Tj,

    Were the values of R1 and R2 (feedback resistors) the same as the EVM? Lower feedback resistor values can cause a higher current draw when talking about uA's. 

    It seems like there is something drawing more than 20uA on the output side to cause it to increase in frequency.

    Thanks,

    Joseph

  • 0 in reply to Joseph Conrad
    Prodigy 10 points

    Hello Conrad,

      Thank you, that was exactly my problem.  I had forgotten I used lower value resistors because I didn't have any large value resistors.  Now the current in PSM mode is really low.  Thanks again!