SBVS311A November 2019 – March 2020 TPS7A54
Controlling when a single power supply turns on can be difficult in a power distribution network (PDN) because of the high power levels inherent in a PDN, and the variations between all of the supplies. As shown in Figure 42 and Table 2, the LDO turnon and turnoff time is set by the enable circuit (EN) and undervoltage lockout circuits (UVLO1,2(IN) and UVLOBIAS).
|INPUT VOLTAGE||BIAS VOLTAGE||ENABLE STATUS||LDO STATUS||ACTIVE DISCHARGE||POWER GOOD|
|VIN ≥ VUVLO_1,2(IN)||VBIAS ≥ VUVLO(BIAS)||EN = 1||On||Off||PG = 1 when VOUT ≥ VIT(PG)|
|EN = 0||Off||On||PG = 0|
|VBIAS < VUVLO(BIAS) + VHYS(BIAS)||EN = don't care||Off||On(1)|
|VIN < VUVLO_1,2(IN) – VHYS1,2(IN)||BIAS = don't care||Off|
|IN = don't care||VBIAS ≥ VUVLO(BIAS)||Off|
VBIAS is not intended to be used dynamically when the IN rail is being powered up. If the BIAS rail is powered down when the IN rail is greater than 1.4 V, the PG output can trip. If the BIAS rail is powered up after the IN rail for VIN ≥ 1.4 V, a non-monotonic startup can occur.