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TPS61253A: Reverse voltage/current protection?

Shawn Swift
Prodigy 165 points
Part Number: TPS61253A
Other Parts Discussed in Thread: TPS61253

Hello,

I'd like to use this boost converter to provide a 5V supply from a Li-ion battery to a circuit that may also be powered by USB, but I can't tell from the the block diagram if there are any conditions under which applying a little over 5V to VOUT may result in reverse current flow through the device back to VIN damaging the battery.

I'm guessing that if the battery voltage drops enough that the device is no longer able to boost it to 5V that the UVLO will kick in and the battery will be protected. And it seems like unlike the TPS61253, the gate driver on the TPS61253A is connected to VOUT as well as VIN, so presumably that would still be pulling the PMOS gate high to turn it off even if the battery is disconnected, and the body diodes of the mosfet would prevent reverse current flow, but I'm not certain because the datasheet doesn't show how the gate driver functions.

  • 0
    TI__Mastermind 40080 points
    for the TPS61253A, if the input battery is not connected, this IC is disbaled, which means the PMOSFET is turned off. if the battery connected and it is enabled, when there's a higher than Vo volatge added at the output side, the high side PFET will also turned off.
  • 0 in reply to Helen chen
    Prodigy 165 points

    Am I correct in assuming this protection does not apply in forced PWM mode?

    8.4.2 Forced PWM Mode

    In the forced PWM mode, the TPS6125xA keeps the switching frequency being constant for the whole load

    range. When the load current decreases, the output of the internal error amplifier decreases as well to lower the

    inductor peak current and delivers less power from input to output. The high-side FET is not turned off even if the

    current through the FET goes negative to keep the switching frequency being the same as that of the heavy load.

  • 0 in reply to Helen chen
    Prodigy 165 points

    Also, does the FET still turn off with negative current in Ultrasonic mode during light loads where the PWM frequency is always kept above 25KHz?

    8.4.3 Ultrasonic Mode

    The ultrasonic mode is an unique control feature that keeps the switching frequency above the acoustic audible

    frequency toward no load condition. The ultrasonic mode control circuit monitors the switching frequency and

    keeps the switching frequency above 25 kHz to avoid the acoustic band. The output voltage becomes typically

    1.6% higher than PWM operation. Figure 21 illustrates the details of ultrasonic mode operation.

  • 0 in reply to Shawn Swift
    TI__Mastermind 40080 points

    If you want to add a higher voltage at the TPS61253A's output when it is  working. then please set it at the PFM mode. Both the PWM mode and the Ultrasonic mode will have big reverse current.