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Original question:

TPS48111Q1EVM: Does TPS48111 charge-pump undervoltage flag reliably indicate MOSFET V_GS undervoltage, or should I add separate...

TPS48111Q1EVM: Is the source node always pulled to V_BATT by the driver?

Michelle Mathew
Prodigy 190 points
Part Number: TPS48111Q1EVM

Tool/software:

Hi TI team,

In a high-side configuration with TPS48111:

  • Does the gate driver always pull the MOSFET source up to V_BATT when turning on?

  • Or are there conditions where the source may not rise fully to V_BATT (eg. EN pin low, body diode conduction, etc)

Thank You,

Michelle Mathew

  • 0
    TI__Expert 8820 points

    Hi Michelle, 

    The TPS4811 has a very strong gate drive PU current coupled with the boot strap capacitor that will enhance the FET gate and make the VBAT = SRC. 

    The device pulls SRC to PD during turn off cases. 

    If you are experiencing a scenario where the SRC is not fully rising to VBAT then it is likely that the VGS is not enhanced properly and you may be experiencing insufficient boot strap capacitance or improper SRC connections. 

    Thanks, 

    Sarah

  • 0 in reply to Sarah Raines
    Prodigy 190 points

    Hi Sarah,

    Thank You for the reply.

    I believe gate voltage being pulled to PU during turn ON and PD during turn OFF indicates the voltage at the gate, and subsequently the V_GS. But would the source of the MOSFET be pulled to V_BATT in both cases. Is there any scenario where the source is pulled to ground.

    Regards,

    Michelle 

  • 0 in reply to Michelle Mathew
    TI__Expert 8820 points

    Hi Michelle, 

    Yes. The SRC pin is connected directly to the SRC of the FET. During PU the drain side connected to VBATT will conduct to SRC making SRC == VBATT. 

    During PD the SRC pin will get pulled down to an approximation of GND.

    Thanks, 

    Sarah