In the reverse battery condition, the switch will automatically be enabled regardless of the state of the output (set by the SW_STATE register) to prevent excess power dissipation inside the MOSFET body diode. In many applications (for example, resistive loads), the full load current may be present during reverse battery. In order to activate the automatic switch on feature, the DI pin (version A) or DI1 (version B) must have a path to ground from either from the MCU or it needs to be tied to ground through R_PROT if unused.

There are two options for handling reverse battery in the system. The first option is to place a blocking device (FET or diode) in series with the battery supply, blocking all current paths. The second option is to place a blocking diode in parallel with a resistor on the GND node of the high-side switch. This method will protect the controller portion of the switch (path 2) by limiting the current through the internal circuits. Additionally in the second option, the automatic switch on feature of the device will allow the device to be put into low R_ON state to allow current to flow through the switch efficiently and through the load (path 3). The diode used for the second option may be shared amongst multiple high-side switches.

Figure 8-32 Current Path During Reverse Battery

For more information on reverse battery protection, refer to TI's Reverse Battery Protection for High Side Switches application note.