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TPS7H1101A-SP: Output voltage question of "TPS7H1101A-SP"

Kim JoonHyun
Prodigy 60 points
Part Number: TPS7H1101A-SP

I designed a schematic diagram as shown in the picture below, but the output voltage is not working.

What's wrong?

  • +1
    TI__Guru 62930 points

    Kim, I can help.   However, it is difficult to read your schematic fully, as it is low resolution.

    I can see one issue, and that is you have tied PCL to Vin through a resistor.  This will make the device think it is in overcurrent condition regardless of load.

    RPCL needs to be connected through resistor to ground.   Additionally, with Vcs greater than 0.9 of Vref, the overcurrent trip will put the device in foldback mode.  

    Since the current limit trip point is not valid (as Vpcl is greater then Vref regardless of load), it is uncertain of device behavior under this condition.

    If you post higher resolution schematic, I can review further if desired.

    If this answers your question, please click "This Resolved My Issue"
    Regards,
    Wade

  • 0 in reply to Wade Vonbergen
    TI__Guru 62930 points

    Kim,

    For some reason I was not able to see the higher resolution capture of your schematic the first time.

    Now that I can see it better, I have some additional comments.

    The prior comments are still valid, and RPCL needs to be connected through resistor to ground to allow the device to operate out of current limiting.

    If you are planning on sensing the current through Vcs, then you may want to increase Rcs to allow a larger drop through it. 

    For example, with your 9.53K resistor, at 3A, the minimum Vcs voltage will be 4.81V (dropping from 5V)

    If you are not sensing Vcs, then this is not an issue.

    Once Rpcl is connected to ground, your 8.25K resistor will set a foldback mode current limit of min (3.34 A, nom 3.85 A, max 4.8 A)

    To set the min current limit to 3A, this would imply an Rpcl of 9.2K.    Larger values would reduce the limit further.

    If you desire brick mode current limiting (vs foldback), then you will need to adjust Vcs so it will be less than 0.544 V.  With your current RCS, it will stay in foldback mode.

    Hopefully this helps.

    Regards,

    Wade