Datasheet

EN1
PWRGD1
VOUT1
VOUT2
SS /TR
TPS54140A
EN
PWRGD
SS /TR
EN
PWRGD
TPS54140A
www.ti.com SLVSB55B –MAY 2012–REVISED JANUARY 2014
DETAILED DESCRIPTION (continued)
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 TPS54140A devices. The power good is
coupled to the EN pin on the TPS54140A which will enable the second power supply once the primary supply
reaches regulation. If needed, a 1nF 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.
Figure 32. Schematic for Sequential Start-Up Figure 33. Sequential Startup using EN and
Sequence PWRGD
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