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TPS65150: VGH pin cannot reach 22V.

Kevin Lai
Intellectual 2916 points
Part Number: TPS65150

Hi,

My customer is in need of support. please read below:

"I'm currently working on a LCD Display power supply, using TI's TPS65150 chip to produce 4 voltages from a source voltage of +2.5V. I had a prototype PCB made and the circuit mostly functions, except the VGH voltage won't get up to +22V where I need it. I can only reach +16V. I tried adding another charge pump stage as suggested on pg17 of the spec sheet but that just resulted in an unstable output that eventually led to the chip going into shutdown mode. I attached the spec sheet I'm using and the specific design I've worked up. Think you can provide any clarity on this?"

Thanks,

Kevin

  • 0
    TI__Mastermind 18550 points

    Hello Kevin,

    Thank you for your post. we will look into this issue in more detail and get back to you by 10/22.

    Kind Regards,

    Liaqat

  • 0
    TI__Mastermind 18550 points

    Hi Kevin,

     

    From the schematics, Vvs=8.2V and customer wants 22V for VGH so a charge pump doubler is definitely not going to work.

    With charge pump trippler (8.2X3=24.6V), there would be barely enough headroom to regulate to VGH=22V assuming 2V for forward voltage drop of the four diodes and some more drop across Rdson of the internal FET. So I am thinking that perhaps there is not enough headroom even with the trippler.

    To find out if charge pump tripler is not providing correct 22V VGH due to not having enough headroom, can you please request customer to increase Vvs slightly to 8.6V and see if VGH regulates to 22V properly? I would expect it to regulate properly in this case.

    Other than this possible headroom issue, I don’t see anything else wrong with the schematics.

    Kind Regards,

    Liaqat