Datasheet
Adjusting the Output Voltage of the PTH12040W Wide-Output Adjust Power Module
R
set
+ 10 kW
0.8 V
V
O
* 0.8 V
* 1.696 kW
(1)
PTH12040W
12
15
9
1
3
5
10 13 16
11
14
+Sense
-Sense
-Sense
GND GND
17
+Sense
GND
R
1%
0.05W
SET
V
O
V
O
C
330 F
O
m
C
330 F
O
m
V Adj
O
PTH12040W
www.ti.com
............................................................................................................................................... SLTS237G – DECEMBER 2004 – REVISED MARCH 2009
The V
O
Adjust control (pin 17) sets the output voltage of the PTH12040W product. The adjustment range is from
0.8 V to 5.5 V. The adjustment method requires the addition of a single external resistor, RSET, that must be
connected directly between the V
O
Adjust and GND pins 1. Table 2 gives the preferred value of the external
resistor for a number of standard voltages, along with the actual output voltage that this resistance value
provides. Figure 8 shows the placement of the required resistor.
For other output voltages, the value of the required resistor can either be calculated, or simply selected from the
range of values given in Table 3 . The following formula can be used to calculate the adjust resistor value.
Table 2. Standard Values of R
SET
for Common Output
Voltages
PTH12040W
V
O
(Required) (V) R
SET
(k Ω ) V
O
(Actual) (V)
5.0 0.210 5.002
3.3 1.50 3.303
2.5 3.01 2.50
2.0 4.99 1.997
1.8 6.34 1.796
1.5 9.76 1.498
1.2 18.2 1.202
1.0 38.3 1.0
0.8 Open 0.8
(1) A 0.05-W rated resistor may be used. The tolerance should be 1%, and the temperature stability, 100 ppm/ ° C (or
better). Place the resistor as close to the regulator as possible. Connect the resistor directly between pin 17 and the
nearest GND pin (pin 16) using dedicated PCB traces.
(2) Never connect capacitors directly from V
o
Adjust to either GND or V
O
. Any capacitance added to the V
o
Adjust pin
affects the stability of the regulator.
Figure 8. V
O
Adjust Resistor Placement
Copyright © 2004 – 2009, Texas Instruments Incorporated Submit Documentation Feedback 11
Product Folder Link(s): PTH12040W