The voltage applied at EN1 and EN2 is compared to a fixed threshold of 1.1 V for a rising voltage. This comparison allows the user to drive the pin by a slowly changing voltage and enables the use of an external RC network to achieve a power-up delay.

The precise enable input provides a user-programmable undervoltage lockout by adding a resistor divider to the input of EN1 and EN2.

The enable input threshold for a falling edge is typically 100 mV lower than the rising edge threshold. The TPS6244x starts operation when the rising threshold is exceeded. For proper operation, the enable (EN) pin must be terminated and must not be left floating. Pulling the enable pin low forces the device into shutdown, with a shutdown current of typically 1.5 μA. In this mode, the internal high-side and low-side MOSFETs are turned off and the entire internal control circuitry is switched off.

The enable delay time is defined from EN1 or EN2 going high to when the converter starts switching. The converter is enabled first, the internal bandgap is started, and bias currents and configuration bits are read, so its start-up delay time is longer than for the converter being enabled when this is already done.