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TPS65150 doesn't Start-up

Gaurav Agrawal
Intellectual 735 points
Other Parts Discussed in Thread: TPS65150

Hi,

I am using TPS65150 for powering an automotive LCD system design, please see schematic attached.4174.Schematic_TPS65150.pdf

Voltage at VDDLCD is 5V, but strangely I do not see any output on the AVDD net which should be 11V as per schematic. I just see 4.9V which is D1 output, meaning that Vs booster of TPS65150 is not in regulation. Also tried to check output voltage on REF pin but I just see 0V.

Is there anything basic that I am missing here? Please suggest.

Regards

Gaurav

  • 0
    Intellectual 735 points

    And just to add, there is no load currently on AVDD output.

  • 0 in reply to Gaurav Agrawal
    TI__Guru 65470 points

    Hello Gaurav,

    The AVDD is set to be 11.07V and the output of the positive charge pump is set to be 20V.

    I could imagine that the positive charge pump is not able to deliver the right output voltage and the fault protection turns the IC off again. The charge pump is able to deliver 2*AVDD minus all the losses in the system from the diodes and the DRVP circuit, so this could be marginal.

    Please check the output voltages with an oscilloscope when you apply VIN. Does the part try to start and turn off shortly after start or does it not start at all.

    Another test would be to increase AVDD to e.g. 13V and check if the system starts then.

    Best regards,
    Brigitte 

  • 0 in reply to Brigitte
    Intellectual 735 points

    Hi Brigitte,

    Thanks for your mail. We checked everything, and there was an issue with the thermal pad not properly soldered. The device started up as soon as this was fixed and all voltages were achieved as desired.

    Now, however, we are stuck with a strange issue. As soon as the 7" LCD was plugged in, the 5V input to TPS65150 (VDDLCD in the schematic diagram attached earlier) gets shorted to Ground and the board is shut off. This happened on two boards, and we are kind of stuck now and trying to debug before we power on another board.

    Any inputs would be highly appreciated. The 5V net is not going to any other component and solely being used for the TPS65150 operation.

    Regards

    Gaurav

  • 0 in reply to Gaurav Agrawal
    TI__Guru 65470 points

    Hello Gaurav,

    Are you plugging in the module while TPS65150 is already supplied or are you first plugging in and then turning on the device?

    What happens when you plug in the module with the IC not powered and measure the resistance from VIN to GND?

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Intellectual 735 points

    Hi Brigitte,

    Many thanks for the quick reply.

    We are first plugging in the LCD module, and then powering up the device.

    When module is plugged in, and no power is applied, the resistance from Vin to GND is in few KOhms.

    The module datasheet is cross checked again for all current values and they are well within the range of TPS65150.

    Regards

    Gaurav

  • 0 in reply to Gaurav Agrawal
    TI__Guru 65470 points

    Hello Gaurav,

    Please observe all output voltage during startup with an oscilloscope, otherwise it will be almost impossible to find the root cause for the issue.

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Intellectual 735 points

    Hi Brigitte,

    I will get back to you once we have some results on that.

    Regards

    Gaurav