Datasheet

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ADJUSTING THE OUTPUT VOLTAGE OF THE PTV08040W WIDE-OUTPUT ADJUST POWER
)
V -0.8
O
0.8
-7.135kW
(
R =30.1
SET
x
(1)
PTV08040W
R
1%
0.05W
SET
10
17
3
12 18 19 4 5 11
1
2
V
O
V
O
C 2
O
C 1
O
GND GND
V
O
Adj
8
+Sense
+Sense
-Sense
-Sense
GND
PTV08040W
SLTS257B – SEPTEMBER 2005 – REVISED JANUARY 2008
MODULE
The V
O
Adjust control (pin 8) sets the output voltage of the PTV08040W product. The adjustment range is from
0.8 V to 3.6 V. 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. 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.
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 9 shows the placement of the required resistor.
Table 2. Standard Values of R
SET
for Common Output
Voltages
PTV08040W
V
O
(Required) R
SET
V
O
(Actual)
3.3 V 2.49 k Ω 3.303 V
2.5 V 6.98 k Ω 2.5 V
2.0 V 13.0 k Ω 1.997 V
1.8 V 16.9 k Ω 1.796 V
1.5 V 27.4 k Ω 1.498 V
1.2 V 53.6 k Ω 1.202 V
1.0 V 113 k Ω 1 V
0.8 V Open 0.8 V
Figure 9. V
O
Adjust Resistor Placement
• 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 8
and nearest GND pin (pin 11) using dedicated PCB traces.
• Never connect capacitors 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.
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