ZHCSMS4B November 2020 – September 2021 TPS25864-Q1 , TPS25865-Q1
PRODUCTION DATA
The system undervoltage Lockout (UVLO) is adjusted using the external voltage divider network of RENT and RENB. 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. Equation 12 can be used to determine the VIN UVLO level.
The EN rising threshold (VENH) for the TPS2586x-Q1 is set to be 1.3 V (typical). Choose 10 kΩ for RENB to minimize input current from the supply. If the desired VIN UVLO level is at 6 V, then the value of RENT can be calculated using Equation 13:
Equation 13 yields a value of 36.1 kΩ. The resulting falling UVLO threshold equals 5.5 V and can be calculated by Equation 14, where EN hysteresis (VEN_HYS) is 0.1 V (typical).
Note that it cannot connect EN to IN pin directly for self-startup. Because the voltage rating of EN pin is 11 V, tying it to VIN directly damages the device. The simplest way to enable the operation of the TPS2586x-Q1 is to connect the EN to VSENSE. This connection allows the automatic startup when VIN is within the operation range.