C

= 0.01

F

SS1

m

R1 = 33 mW

C

= 0.022

F

SS1

m

R1 = 143 mW

C

= 0.022

F

SS1

m

C

= 0.01

F

SS1

m

5

OUT

F B

6

R

V

= V

+1

R

æ

ö

ç

÷

è

ø

TPS75003-EP

SGLS311A

– DECEMBER 2006 – REVISED MARCH 2011

www.ti.com

This soft-start current limit ramo can be used to provide inrush current control or output voltage ramp control.

While the current limit ramp can be easily understood by looking at Figure 25, the output voltage ramp is a

to get the desired startup profile. To stay above a minimum start-up time, set the nominal start-up time to

approximately five times the minimum. To stay below a maximum time, set the nominal start-up time at one-fifth

Slowest start-up times occur under opposite conditions.

See Figure 11 to Figure 14 for characterization curves showing how the start-up profile is affected by these

critical parameters.

Output Voltage Setting Selection (Buck Controllers)

Output voltage is set using two resistors as shown for Buck2 in Figure 2. Output voltage is then calculated using

Equation 13.

(13)

LDO OPERATION

The TPS75003 LDO uses a PMOS pass element and is offered in an adjustable version for ease of

other output voltages to power other circuitry. The LDO has integrated soft-start, independent enable, and

3.3-V JTAG signals are used as described in Application Note SLVA159 (available for download from

www.ti.com).

Input Capacitor Selection (LDO)

Although an input capacitor is not required, it is good analog design practice to connect a 0.1-

μF to 10-μF low

ESR capacitor across the input supply near the regulator. This capacitor counteracts reactive input sources and

improves transient response, stability, and ripple rejection. A higher value capacitor may be needed if large, fast

rise-time load transients are anticipated, or if the device is located far from its power source.

18

Copyright

© 2006–2011, Texas Instruments Incorporated

Product Folder Link(s): TPS75003-EP