SLVS875C January 2009 – November 2014 TPS54332
The EN pin has an internal pullup current source that provides the default condition of the TPS54332 operating when the EN pin floats.
The TPS54332 is disabled when the VIN pin voltage falls below internal VIN UVLO threshold. TI recommends using an external VIN UVLO to add Hysteresis unless VIN is greater than (VOUT + 2 V). To adjust the VIN UVLO with Hysteresis, use the external circuitry connected to the EN pin as shown in Figure 11. Once the EN pin voltage exceeds 1.25 V, an additional 3 μA of hysteresis is added. Use Equation 1 and Equation 2 to calculate the resistor values needed for the desired VIN UVLO threshold voltages. The VSTART is the input start threshold voltage, the VSTOP is the input stop threshold voltage and the VEN is the enable threshold voltage of 1.25 V. The VSTOP should always be greater than 3.5 V.