Datasheet
R
SET
=10k xW
0.69
V -0.69
O
-1.43k W
+Sense
PTH08T260W
5
4
3
−Sense
GND
+Sense
−Sense
GND
9
6
V
O
Adj
R
SET
1%
0.05 W
V
O
V
O
UDG−06080
PTH08T260W, PTH08T261W
SLTS272G –DECEMBER 2006– REVISED AUGUST 2011
www.ti.com
APPLICATION INFORMATION
ADJUSTING THE OUTPUT VOLTAGE
The V
O
Adjust control (pin 7) sets the output voltage of the PTH08T260/261W. The adjustment range is 0.69 V to
5.5 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 the –Sense pins. 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 required resistor value can either be calculated using the following formula, or
simply selected from the values given in Table 2. Figure 9 shows the placement of the required resistor.
(1)
Table 1. Preferred Values of R
SET
for Standard Output Voltages
V
O
(Standard) (V) R
SET
(Standard Value) (kΩ) V
O
(Actual) (V)
5.0
(1)
0.169 5.01
3.3 1.2 3.30
2.5 2.37 2.51
1.8 4.7 1.81
1.5 6.98 1.51
1.2
(2)
12.1 1.20
1.0
(2)
20.5 1.01
0.7
(2)
681 0.70
(1) For V
O
> 3.6 V, the minimum input voltage is (V
O
+ 2) V.
(2) For output voltages ≤ 1.2V, at nominal operating frequency, the output ripple may increase (typically
2×) when operating at input voltages greater than (V
O
× 11). When using the SmartSync feature,
review the SmartSync application section for further guidance.
(1) R
SET
: Use a 0.05 W resistor with a tolerance of 1% and temperature stability of 100 ppm/°C (or better). Connect the
resistor directly between pins 7 and 6, as close to the regulator as possible, using dedicated PCB traces.
(2) Never connect capacitors from V
O
Adjust to either GND, V
O
, or +Sense. Any capacitance added to the V
O
Adjust pin
affects the stability of the regulator.
Figure 9. V
O
Adjust Resistor Placement
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