Datasheet

TPS65251
GND
VIN
LX3
VIN
LX3
GND
BST3
VIN3
EN3
FB1
SS1
SYNC CMP1
ROSC RLIM1 CMP3 RLIM3
FB3
SS3
LX2
BST2
LX1
VIN2
LX2
EN2
VIN1
EN1
LX1
BST1
CMP2
GND
FB2
LOW_P
SS2
V7V
AGND
PGOOD
V3V
C11
22uF
R10
40.2K
R11
80.6K
1.2V 3A
L1
4.7uH
C13
4.7nF
R13
100K
C15
100pF
R12
20K
C14
4700pF
V1
VIN1
C10
47nF
C17
4.7nF
VIN
R1
383K
FB2
LP
PG
C1
10uF
C2
3.3uF
VIN
C16
4.7nF
RLIM2
TPS65251
www.ti.com SLVSAA4D –JUNE 2010–REVISED DECEMBER 2012
APPLICATION INFORMATION
Design Guide - Step-By-Step Design Procedure
The following example illustrates the design procedure for selecting external components for the three buck
converters. The example focuses on Buck 1, but the procedure can be directly applied to Buck 2 and 3 as well.
The design goal parameters are given in Table 1.
Table 1. Design Parameters
Output voltage 1.2 V
Transient response 0.5-A to 2-A load step 120 mV
Maximum output current 3 A
Input voltage 12 V nom, 9.6 V to 14.4 V
Output voltage ripple < 30 mV p-p
Switching frequency 500 kHz
Typical Buck 1 Application Schematic
The application schematic of Buck 1 is shown in Figure 32. The design procedure is given below.
Figure 32. Typical Buck 1 Application Circuit
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