8.2.2.8 UVLO Set Point

The designer can adjust the UVLO using an external voltage divider on the EN pin of the TPS57140-EP. The UVLO has two thresholds, one for power up when the input voltage is rising and one for power down or brownouts when the input voltage is falling. For the example design, the supply should turn on and start switching when the input voltage increases above 7.25 V (enabled). After the regulator starts switching, it should continue to do so until the input voltage falls below 6.25 V (UVLO stop).

Set the programmable UVLO and enable voltages by using a resistor divider between Vin and ground to the EN pin. Use Equation 2 through Equation 3 to calculate the resistance values necessary. For the example application, 332 kΩ between Vin and EN and 61.9 kΩ between EN and ground are required to produce the 7.25- and 6.25-V start and stop voltages.