Datasheet
EN
SS/TR
V
SENSE
VOUT
TPS54040A
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SLVSB58A –MARCH 2012–REVISED JANUARY 2014
DETAILED DESCRIPTION (continued)
Figure 31. Operation of SS/TR Pin when Starting
Overload Recovery Circuit
The TPS54040A has an overload recovery (OLR) circuit. The OLR circuit will slow start the output from the
overload voltage to the nominal regulation voltage once the fault condition is removed. The OLR circuit will
discharge the SS/TR pin to a voltage slightly greater than the VSENSE pin voltage using an internal pull down of
100μA when the error amplifier is changed to a high voltage from a fault condition. When the fault condition is
removed, the output will slow start 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 32 using two TPS54040A devices. The power good is
coupled to the EN pin on the TPS54040A which will enable 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 will provide a
1ms start up delay. Figure 33 shows the results of Figure 32.
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