The enable (EN) pin is active high and compatible with standard digital signaling levels. V_EN lower than 0.4V turns the regulator off, whereas V_EN above 1.1V turns the regulator on. Unlike many regulators, the enable circuitry has hysteresis and deglitching for use with relatively slow-ramping analog signals. This configuration allows the TPS74401 to be enabled by connecting the output of another supply to the EN pin. The enable circuitry typically has 50mV of hysteresis and a deglitch circuit to help avoid on-off cycling resulting from small glitches in the V_EN signal.

The enable threshold is typically 0.8V and varies with temperature and process variations. Temperature variation is approximately –1mV/°C; therefore, process variation accounts for most of the variation in the enable threshold. If precise turn-on timing is required, use a fast rise-time signal to enable the TPS74401.

If not used, EN can be connected to either IN or BIAS. If EN is connected to IN, connect EN as close as possible to the largest capacitance on the input to prevent voltage droops on that line from triggering the enable circuit.