JAJS381E September 2009 – September 2018 TPS54218
PRODUCTION DATA.
The undervoltage lockout (UVLO) can be adjusted using an external voltage divider on the EN pin of the TPS54218. The UVLO has two thresholds, one for power up when the input voltage is rising and one for power down or brown outs when the input voltage is falling. For the example design, the supply should turn on and start switching once the input voltage increases above 3.1 V (VSTART). Switching continues until the input voltage falls below 2.8 V (VSTOP).
The programmable UVLO and enable voltages are set using a resistor divider between the VIN pin and GND to the EN pin. Equation 32 and Equation 33 can be used to calculate the resistance values necessary. From Equation 32 and Equation 33, a 48.7 kΩ between the VIN pin and the EN pin and a 32.4-kΩ resistor between the EN pin and GND are required to produce the 3.1-V start voltage and the 2.8-V stop voltage.