Datasheet

V
OUT
+ V
REF
ǒ
1 )
R
11
R
12
Ǔ
with an internal reference voltage V
REF
typical 0.6V
V
OUT
+ V
REF
ǒ
1 )
R
21
R
22
Ǔ
with an internal reference voltage V
REF
typical 0.6V
SW1
FB1
SW2
ADJ2
DEF_1
VIN3.3V – 6V
VIN
EN_1
EN_2
MODE/
DATA
TPS62420
GND
L1
C
10 F
IN
m
2.2 Hm
R11
270kW
R12
180kW
V =1.5V
upto600mA
OUT1
C =22 F
OUT1
m
V =2.85V
upto1000mA
OUT2
L2
C
ff2
33pF
3.3 Hm
R21
825kW
R22
220kW
C =22 F
OUT2
m
TPS62420, TPS62421
www.ti.com SLVS676C –JUNE 2006–REVISED JUNE 2010
APPLICATION INFORMATION
OUTPUT VOLTAGE SETTING
Converter1 Adjustable Default Output Voltage Setting
The output voltage can be calculated to:
(4)
To keep the operating current to a minimum, it is recommended to select R
12
within a range of 180kΩ to 360kΩ.
The sum of R
12
and R
11
should not exceed ~1MΩ. For higher output voltages than 3.3V, it is recommended to
choose lower values than 180kΩ for R12. Route the DEF_1 line away from noise sources, such as the inductor
or the SW1 line. The FB1 line needs to be directly connected to the output capacitor. An internal feed forward
capacitor is connected to this pin, therefore there is no need for an external feed forward capacitor for converter
1.
Converter 2
The default output voltage of converter 2 can be set by an external resistor network. For converter 2 the same
recommendations apply as for converter 1. In addition to that, a 33pF external feed forward capacitor C
ff2
for
good load transient response must be used.
The output voltage can be calculated to:
(5)
Route the ADJ2 line away from noise sources, such as the inductor or the SW2 line. In case the interface is used
for converter2, connect ADJ2 pin directly to V
OUT2
Figure 34. Typical Application Circuit 1.5V/2.85V Adjustable Outputs
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