Datasheet

V
EN
V
SS/TR
V
VSENSE
V
OUT
TPS5401
SLVSAB0 –DECEMBER 2010 www.ti.com
DETAILED DESCRIPTION (continued)
Figure 29. Operation of SS/TR Pin When Starting
Overload Recovery Circuit
The TPS5401 has an overload recovery (OLR) circuit. The OLR circuit slow-starts the output from the overload
voltage to the nominal regulation voltage once the fault condition is removed. The OLR circuit discharges the
SS/TR pin to a voltage slightly greater than the VSENSE pin voltage using an internal pulldown of 100 mA when
the error amplifier is changed to a high voltage from a fault condition. When the fault condition is removed, the
output slow-starts from the fault voltage to nominal output voltage.
Sequencing
Many of the common power-supply sequencing methods can be implemented using the SS/TR, EN and PWRGD
pins. The sequential method can be implemented using an open-drain output of a power-on-reset pin of another
device. The sequential method is illustrated in Figure 30 using two TPS5401 devices. The power good is coupled
to the EN pin on the TPS5401, which enables the second power supply once the primary supply reaches
regulation. If needed, a 1-nF ceramic capacitor on the EN pin of the second power supply provides a 1-ms
start-up delay. Figure 31 shows the results of Figure 30.
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