Datasheet
P
OUT OUT
1
F =
2 L C´p
OUT
R1
V = 0.765 1+
R2
æ ö
´
ç ÷
è ø
C1
L1
R2
22.1k
R1 8.25k
C5
1uF
EN
VFB
VREG5
SS
VIN
4.5 to 18V
10uF
C2
C3
10uF
0.1uF
1
2
3
4
VIN
VBST
SW
GND
8
7
6
5
VOUT
C6
8200pF
PwPd
1.5uH
1
C4
2
U1
TPS54427DDA
9
1
R3 10.0k
C7 0.1uF
C8
22uF
VOUT
C9
22uF
VIN
1
Not Installed
EN
VOUT
1.05V 4A
TPS54427
www.ti.com
SLVSB43A –NOVEMBER 2011–REVISED JUNE 2013
DESIGN GUIDE
Step By Step Design Procedure
To begin the design process, you must know a few application parameters:
• Input voltage range
• Output voltage
• Output current
• Output voltage ripple
• Input voltage ripple
Figure 14. Shows the Schematic Diagram for this Design Example
Output Voltage Resistors Selection
The output voltage is set with a resistor divider from the output node to the VFB pin. It is recommended to use
1% tolerance or better divider resistors. Start by using Equation 2 to calculate V
OUT
.
To improve efficiency at very light loads consider using larger value resistors, too high of resistance will be more
susceptible to noise and voltage errors from the VFB input current will be more noticeable.
(2)
Output Filter Selection
The output filter used with the TPS54427 is an LC circuit. This LC filter has double pole at:
(3)
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