5V

1.8V

1.8V

5V

1.8V

LM2744

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SNVS292E – SEPTEMBER 2004 – REVISED JANUARY 2012

Figure 4. Tracking with Equal Soft-Start Time

TRACKING A VOLTAGE SLEW RATE

The tracking feature can alternatively be used not to make both rails reach regulation at the same time but rather

to have similar rise rates (in terms of output dV/dt). This method ensures that the output voltage of the LM2744

always reaches regulation before the output voltage of the master supply. In this case, the tracking resistors can

be determined based on the following equation:

(5)

above equation to be 267

Ω. A timing diagram for the case of equal slew rates is shown in Figure 5.

Figure 5. Tracking with Equal Slew Rates

SEQUENCING

The start up/soft-start of the LM2744 can be delayed for the purpose of sequencing by connecting a resistor

divider from the output of a master power supply to the SD pin, as shown in Figure 6.

Copyright © 2004–2012, Texas Instruments Incorporated

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