Datasheet

VIN
4.5to18V
10
VOUT
1.05V,2A
U1
TPS542225PWP
11
9
12
6
3
8
SW1
SW2
PGND2
VBST
PG
VREG5
PGND1
14
15
13
5
1
2
4
7
VCC
VIN
GND
VO
VFB
SS
EN
PwPd
V =
OUT
0.765 •
(1+
R1
R2
−
)
V = V
OUT OUT
(0.763+0.0017 )• •
(1+
R1
R2
−
)
1
2
P
OUT OUT
F
L Cp
=
´
TPS54225
SLVSA15C –OCTOBER 2009– REVISED FEBRUARY 2011 www.ti.com
DESIGN GUIDE
Step By Step Design Procedure
To begin the design process, the following application parameters must be known:
• Input voltage range
• Output voltage
• Output current
• Output voltage ripple
• Input voltage ripple
Figure 13. Schematic Diagram
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 and Equation 3 to calculate V
OUT
.
To improve efficiency at light loads consider using larger value resistors, too high of resistance is more
susceptible to noise and voltage errors from the VFB input current is more noticeable.
For output voltage from 0.76 V to 2.5 V:
(2)
For output voltage over 2.5 V:
(3)
Where:
V
OUT_SET
= Target V
OUT
voltage
Output Filter Selection
The output filter used with the TPS54225 is an LC circuit. This LC filter has double pole at:
(4)
12 © 2009–2011, Texas Instruments Incorporated
Product Folder Link(s): TPS54225