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6

SS

S0204-01

Shutdown

TPS40077

6

6

4

4

SS

SS

ToSystemPowerGood

PGD

PGD

S0205-01

TPS40077

TPS40077

BOOST AND LVBP BYPASS CAPACITANCE

TPS40077

SLUS714 – JANUARY 2007

APPLICATION INFORMATION (continued)

Figure 26. TPS40077 Shutdown

In a similar manner, power supplies based on the TPS40077 can be sequenced by connecting the PGD pin of

the first supply to come up to the SS pin of the second supply as shown in Figure 27.

Figure 27. TPS40077 Sequencing

The BOOST capacitance provides a local, low-impedance flying source for the high-side driver. The BOOST

capacitor should be a good-quality, high-frequency capacitor. A capacitor with a minimum value of 100-nF is

suggested.

The LVBP pin must provide energy for both the synchronous MOSFET and the high-side MOSFET (via the

BOOST capacitor). The suggested value for this capacitor is 1-

µF ceramic, minimum.

20

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