TPS65135 Datasheet, PDF (14/21 Pages) Texas Instruments – Single-Inductor, Multiple-Output (SIMO) Regulator

TPS65135
SLVS704A – NOVEMBER 2011 – REVISED NOVEMBER 2011
www.ti.com
Output Capacitor Selection
A 4.7-µF output capacitor is generally sufficient for most applications, but larger values can be used as well for
improved load- and line-transient response at higher load currents. The capacitors of Table 4 is recommended
for use with the TPS65135.
CAPACITOR
10 µF / 6.3V
4.7 µF / 10V
10 µF / 6.3 V
Table 4. Output Capacitor Selection
COMPONENT SUPPLIER
Murata GRM188R60J106ME84D
Taiyo Yuden LMK107BJ475
Taiyo Yuden JMK107BJ106
SIZE
0603
0603
0603
SPACER
Setting the Output Voltages OUTP and OUTN
The feedback divider R1, R2, R3 sets the positive and negative output voltage. The device regulates the feeback
voltage FB to typically 1.24 V and the feedback FBG to typically 0V. R2 is selected to have at least 10 µA
through the feedback divider.
1.24V
R2 =
» 120kW
10mA
(7)
The positive output voltage and R1 are calculated as:
V
POS
=
1.24V
×
R1+ R2
R2
(8)
R1 =
R2 ×
æV
çè
POS
1.24V
-
ö
1_÷ø
(9)
The negative output voltage is calculated as:
( ) ^R3
V
NEG
=
-
V
FB
+
V
FBG
×
R2
(10)
Since V_FBG is typically regulated to 0 V, the formula can be simplified and R3 is then calculated as:
V
R3
=
NEG
1.24V
× R2
(11)
PCB Layout Guidelines
PCB layout is an important task in the power supply design. Good PCB layout minimizes EMI and allows very
good output voltage regulation. For the TPS65135 the following PCB layout guidelines are recommended.
Place the power components first. The inductor and the input and output capacitors must be as close as possible
to the IC pins. Place the bypass capacitor for the reference output voltage VAUX as close as possible to pin 4.
Use bold and wide traces for power traces connecting the inductor and input and output capacitors. Use a
common ground plane or a start ground connection.
See the TPS65135EVM-063 user's guide (SLVU244) and evaluation module for a PCB layout example.
14
Copyright © 2011, Texas Instruments Incorporated
Product Folder Link(s): TPS65135