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TPS65186: chip does not come up when PWRUP pin is pulled high.

Part Number: TPS65186

I have created a PCB with the reference design from the data sheet.  Although the chip wakes up and can communicate through the I2C, I cannot get it to power up the supplies.  When PWRUP is pulled high, the oscillator begins running for the negative supply, and I see about -2 volts on VN  with a meter.  The chip then shuts down and asserts either VCOMF or VN_UL.  The VCOM pin is tied low to disable it.

  • Hi,

    I have assigned your request to responsible Applications Engineer and we will get back to you as soon as possible.

    Regards,

    Murthy
  • Hi Donald,

    If VN cannot regulate, the device will not continue to boot.Can you scope VIN to ensure the input supply is stable during startup?

    Please ensure the power-pad is not connected to GND, and that the diode and inductor for VN have adequate current ratings.

    Best Regards,

    Rick S.

  • Thanks Rick.  I will scope VN next.  I reviewed my schematic against the data sheet and found I accidentally used a 100nF instead of a 10nF on the VEE_DRV pin.  Would this cause my issue?  I have not yet had a chance to replace the cap and scope the line.

    I did verify that the power-pad is not connected to GND.  It is connected to VN.  For the inductor I used  VLS252012CX-4R7M-1  which is 4.7UH 1.24A 210 MOHM.  For the diode I used TSSA3U45 R3G which is a SCHOTTKY 45V 3A DO214AC diode.  Do these parts seem suitable?  I thought they were overkill.  I was looking for larger parts since we are building the prototypes by hand.

    I will post the waveforms when I get them. Thanks for your help.

    Don