This pin combines two independent functions.
Disable Mode: A rapid shutdown of the chip is accomplished by externally forcing SS/DISB below 0.5 V, externally forcing REF below 4 V, or if VDD drops below the undervoltage lockout threshold. In the case of REF being pulled below 4 V or an undervoltage condition, SS/DISB is actively pulled to ground via an internal MOSFET switch.
If an overcurrent fault is sensed (CS = 2.5 V), a soft stop is initiated. In this mode, SS/DISB sinks a constant current of (10 × IRT). The soft stop continues until SS/DISB falls below 0.5 V. When any of these faults are detected, all outputs are forced to ground immediately.
If SS/DISB is forced below 0.5 V, the pin starts to source current equal to IRT. The only time the part switches into low IDD current mode, though, is when the part is in undervoltage lockout.
Soft Start Mode: After a fault or disable condition has passed, VDD is above the start threshold, and, or, SS/DISB falls below 0.5 V during a soft stop, SS/DISB switches to a soft-start mode. The pin then sources current, equal to IRT. A user-selected resistor/capacitor combination on SS/DISB determines the soft-start time constant.
SS/DISB actively clamps the EAOUT pin voltage to approximately the SS/DISB pin voltage during soft-start, soft-stop, and disable conditions.