Datasheet

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APPLICATION INFORMATION
Adjusting the Output Voltage of the PTH04070W Wide-Output Adjust Power Modules
R
set
+ 10 kW
0.891 V
V
out
* 0.9 V
* 3.24 kW
Inhibit
GND GND
R
SET
0.05 W
1%
C1
Ceramic
C2
Ceramic
PTH04070W
2
4
31
5
V
O
AdjGND
V
O
V
IN
47-µF 47-µF
V
I
V
O
Inhibit
PTH04070W
SLTS227B – SEPTEMBER 2004 – REVISED OCTOBER 2007
The V
O
Adjust control (pin 4) sets the output voltage of the PTH04070W product. The adjustment range is from
0.9 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 pin 2. Table 1 gives the standard external resistor for a
number of common bus voltages, along with the actual voltage the resistance produces.
For other output voltages, the value of the required resistor can either be calculated using the following formula,
or simply selected from the range of values given in Table 2 . Figure 9 shows the placement of the required
resistor.
Table 1. Standard Values of R
set
for Common Output
Voltages
V
O
(V) R
SET
(k Ω ) V
O
(V)
(Required) (Standard Value) (Actual)
3.3
(1)
0.475 3.298
2.5
(1)
2.32 2.502
2 4.87 1.999
1.8 6.65 1.801
1.5 11.5 1.504
1.2 26.1 1.204
1 84.5 1.001
0.9 Open 0.9
(1) The minimum input voltage is 3 V or (V
O
+ 1.1) V, whichever is
greater.
(1) A 0.05-W rated resistor may be used. The tolerance should be 1%, with a temperature stability of 100 ppm/ ° C (or
better). Place the resistor as close to the regulator as possible. Connect the resistor directly between pins 4 and 2
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 9. V
O
Adjust Resistor Placement
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