Datasheet

( ) ( ) ( )
( )
22
OUTL
IN
RIPPLE IN IN
RIPPLE
1/2 L 0.3 I(1/2)L I
C , MIN =
V V V V
´ ´´ D
»
´ ´
OUT
C,IN(RMS )
IN
V
I
V ,MIN
æ ö
»
ç ÷
è ø
TPS75003-EP
www.ti.com SGLS311A –DECEMBER 2006– REVISED MARCH 2011
Figure 23. Soft-Start Circuitry
Figure 24. Soft-Start Timing Diagram
Input Capacitor C
IN1
, C
IN2
Selection (Buck Controllers)
It is good analog design practice to place input capacitors near the inputs of the device in order to ensure a low
impedance input supply. A capacitance of 10 μF to 22 μF for each buck converter is adequate for most
applications, and should be placed within 100 mils (0.001 in) of the IN1 and IN2 pins to minimize the effects of
pulsed current switching noise on the soft-start circuitry during the first ~1 V of output voltage ramp. Low ESR
capacitors also help to minimize noise on the supply line. The minimum value of capacitance can be estimated
using Equation 3.
(3)
Note that the capacitors must be able to handle the RMS current in continuous conduction mode, which can be
calculated using Equation 4.
(4)
Copyright © 2006–2011, Texas Instruments Incorporated 15
Product Folder Link(s): TPS75003-EP