The supply terminals have under voltage detection which puts the device in protected mode if one of the supply rails drop below the threshold voltage. This protects the bus and system during an under voltage event on either V_SUP, V_CC or V_IO supply terminals. These faults are internal fault flags and are not indicated via the nFAULT terminal.

During an undervoltage event on V_CC or V_IO the device goes into protected mode and the driver is disabled. After the UV timer expires, the device transitions into sleep mode and the INH pin goes into a high impedance state. In the event of a UV on V_IO where the mode pins are no longer driven, the device transitions into standby mode (due to internal fail safe biasing on the NSTB and EN pins) until the UV timer expires and the device transitions into sleep mode.

The V_CC and V_IO undervoltage detection circuits share the same timer. Therefore, if an undervoltage on one supply occurs and the timers starts, and then during the undervoltage the other supply has an undervoltage event before the first supply recovers the timer does not reset.

Once an under voltage condition is cleared and the supplies have returned to valid levels the device typically needs 200 µs to transition to normal operation.