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UCC27212: VDD voltage not present

Ding Li
Prodigy 150 points
Part Number: UCC27212
Other Parts Discussed in Thread: UCC27712

For the UCC27212:

 

If the VDD is not present, will the top gate and bottom gate output be low or high-Z?

Do I need to add pull-down resistors on the MOSFET gates?

The datasheet does not have the pull-down but the EVM does. Please explain.

  • 0
    TI__Mastermind 20950 points

    Hello Ding,

    thank you for supporting the UCC27712 with your customer. The UCC27712 driver outputs do not have a high Z state. If VDD is at 0V there is a path from the driver output internal device which is a body diode from the driver output to the VDD pin and VCC capacitor. This will result in a clamping of the driver output to the VDD capacitor with 0V.

    Having resistors from gate to source is considered good design practice just to eliminate voltage on the Vgs from any possible leakage current in the MOSFET. The driver will function to limit the Vgs voltage from the above mentioned clamping thru the driver device body diode. Also when VDD has adequate voltage of ~1.5 to 2V the driver will set the pull down internal device in the on state as a power up default. This will also clamp the driver output low with low VDD.

    Please confirm if this addresses your questions, or you can post additional questions on this thread.

    Regards,

    Richard Herring