Datasheet

Output Voltage Selection
VDCDC1
EN_DCDC1
DEFDCDC1
AGND PGND
L1
R1
R2
V
OUT
L
C
OUT
V
CC
VINDCDC1
C
IN
1 Fm
10R
V
bat
V
OUT
+ V
DEFDCDCx
R1 ) R2
R2
R1 + R2
ǒ
V
OUT
V
DEFDCDCx
Ǔ
* R2
Voltage Change on VDCDC3
TPS650250
SLVS843 – DECEMBER 2008 ........................................................................................................................................................................................... www.ti.com
Table 3. Possible Capacitors
CAPACITOR
CASE SIZE COMPONENT SUPPLIER COMMENTS
VALUE
22 µ F 1206 TDK C3216X5R0J226M Ceramic
22 µ F 1206 Taiyo Yuden JMK316BJ226ML Ceramic
22 µ F 0805 TDK C2012X5R0J226MT Ceramic
22 µ F 0805 Taiyo Yuden JMK212BJ226MG Ceramic
10 µ F 0805 Taiyo Yuden JMK212BJ106M Ceramic
10 µ F 0805 TDK C2012X5R0J106M Ceramic
The DEFDCDC1, DEFDCDC2, and DEFDCDC3 pins are used to set the output voltage for each step-down
converter. See Table 4 for the default voltages if the pins are pulled to GND or to Vcc.
Table 4. Voltage Options
PIN LEVEL DEFAULT OUTPUT VOLTAGE
DEFDCDC1 VCC 3.3V
GND 2.80V
DEFDCDC2 VCC 2.5V
GND 1.8V
DEFDCDC3 external voltage divider 0.6V to VinDCDC3
If a different voltage is needed, an external resistor divider can be added to the DEFDCDC1 or DEFDCDC2 pin
as shown below:
When a resistor divider is connected to DEFDCDC1 or DEFDCDC2, the output voltage can be set from 0.6V up
to the input voltage V
bat
. The total resistance (R1+R2) of the voltage divider should be kept in the 1M Ω range in
order to maintain a high efficiency at light load. V
DEFDCDCx
= 0.6V
The output voltage of VDCDC3 is set with an external resistor divider at DEFDCDC3. This pin must not be
connected to GND or VINDCDC3. The value of the resistor divider can be changed during operation to allow
dynamic voltage scaling.
22 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS650250