The EN pin provides precision ON and OFF control for the TPSM5601R5Hx. Once the EN pin voltage exceeds the threshold voltage, the device starts operation. The simplest way to enable the device is to connect EN directly to VIN. This allows the device to start up when V_IN is within its valid operating range. An external logic signal can also be used to drive the EN input to toggle the output on and off and for system sequencing or protection. This input must not be allowed to float.

The TPSM5601R5Hx implements internal undervoltage lockout (UVLO) circuitry on the VIN pin. The device is disabled when the VIN pin voltage is below the internal VIN UVLO threshold. The internal VIN UVLO rising threshold is 3.8 V (typical) with a typical hysteresis of 500 mV.

If an application requires a higher UVLO threshold, the EN input supports adjustable UVLO by connecting a resistor divider from VIN to the EN pin. Applying a voltage of ≥ 1.14 V causes the device to enter standby mode, powering the internal LDO, but not producing an output voltage. Increasing the EN voltage to 1.231 V (typ.) fully enables the device, allowing it to enter start-up mode and starting the soft-start period. When the EN input is brought below 1.121 V (110 mV hysteresis), the regulator stops running and enters standby mode. Further decrease in the EN voltage to below 0.3 V completely shuts down the device.

The TPSM5601R5Hx utilizes a reference-based soft start that prevents output voltage overshoots and large inrush currents as the regulator is starting up. The rise time of the output voltage is about 4 ms.