The TPS2521xx device is internally protected
against steady state negative voltages applied at the input supply pin. The device
blocks the negative voltage from appearing at the output, thereby protecting the load
circuits. There’s no reverse current flowing from output to the input in this condition.
The lowest negative voltage the device can handle at the input is limited to –15 V or
VOUT –21 V, whichever is higher. TI also recommends that all signal pins (for example,
EN/UVLO, PGTH) which are connected to input supply should have a sufficiently large
pullup resistor to limit the current flowing out of these pins during reverse polarity
conditions.