Datasheet
APPLICATION INFORMATION
ADJUSTING THE OUTPUT VOLTAGE
PTH12020x
14
5
6
+
GND
GND
10 9 8
7
GND
V
O
Sense
V
OUT
V
O
Adj
R
SET
, 1%
V
O
Sense
V
OUT
C
OUT
330 mF
Equation 1. Output Voltage Adjust
R
set
+ 10 kW
0.8 V
V
out
* V
min
* R
s
kW
(1)
PTH12020W/L
SLTS208I – MAY 2003 – REVISED MARCH 2009 .............................................................................................................................................................
www.ti.com
The V
O
Adjust control (pin 4) sets the output voltage of the PTH12020W/L. The adjustment range is from 1.2 V to
5.5V for the W-suffix modules, and 0.8V to 1.8V for L-suffix modules. The adjustment method requires the
addition of a single external resistor, R
SET
, that must be connected directly between the V
O
Adjust and GND
pins
(1)
. Table 1 gives the standard value of the external resistor for a number of standard voltages, along with the
actual output voltage that this resistance value provides. For other output voltages the value of the required
resistor can either be calculated using Equation 1 , or simply selected from the range of values given in Table 3 .
Figure 11 shows the placement of the required resistor.
Table 1. Standard Values of R
set
for Standard Output Voltages
PTH12020W PTH12020L
V
O
(V) V
O
(V) V
O
(V)
R
SET
(k Ω ) R
SET
(k Ω )
(Req'd) (Actual) (Actual)
5 V 0.280 5.009 N/A N/A
3.3 V 2.0 3.294 N/A N/A
2.5 V 4.32 2.503 N/A N/A
2 V 8.06 2.010 N/A N/A
1.8 V 11.5 1.801 0.130 1.800
1.5 V 24.3 1.506 3.57 1.499
1.2 V Open 1.200 12.1 1.201
1.1 V N/A N/A 18.7 1.101
1.0 V N/A N/A 32.4 0.999
0.9 V N/A N/A 71.5 0.901
0.8 V N/A N/A Open 0.800
(1) Use a 0.05-W, 1% tolerance with temperature stability of 100 ppm/ ° C (or better) for Rset. Place the resistor directly
between pins 4 and 7 using dedicated PCB traces.
(2) Never connect capacitors from V
O
Adjust to either GND or V
O
. Any capacitance added to the V
O
Adjust pin will affect
the stability of the regulator.
Figure 11. V
o
Adjust Resistor Placement
Use Equation 1 to calculate the adjust resistor value. See Table 2 for parameters, R
s
and V
min
.
Table 2. Adjust Equation Parameters
PARAMETER PTH12020W PTH12020L
V
(MIN)
1.2 V 0.8 V
R
S
1.82 k Ω 7.87 k Ω
8 Submit Documentation Feedback Copyright © 2003 – 2009, Texas Instruments Incorporated
Product Folder Link(s) :PTH12020W/L