Datasheet

Application Notes
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PTH03000W
Adjusting the Output Voltage of the PTH03000W
Wide-Output Adjust Power Modules
The V
o
Adjust control (pin 4) sets the output voltage of
the PTH03000Wproduct. The adjustment range is
from 0.9 V to 2.5 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 GND
pins
1
. Table 2-1 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 the following formula, or
simply selected from the range of values given in Table 2-2.
Figure 2-1 shows the placement of the required resistor.
R
set
= 10 kΩ ·
0.891 V
– 4.99 kΩ
V
out
– 0.9 V
Figure 2-1; V
o
Adjust Resistor Placement
Notes:
1. Use a 0.1 W resistor. 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 1
using dedicated PCB traces.
2. Never connect capacitors from V
o
Adjust to either GND or
V
out
. Any capacitance added to the V
o
Adjust pin will affect
the stability of the regulator.
0.900 Open
0.925 351 kΩ
0.950 173 kΩ
0.975 114 kΩ
1.000 84.1 kΩ
1.025 66.3 kΩ
1.050 54.4 kΩ
1.075 45.9 kΩ
1.100 39.6 kΩ
1.125 34.6 kΩ
1.150 30.7 kΩ
1.175 27.4 kΩ
1.200 24.7 kΩ
1.225 22.4 kΩ
1.250 20.5 kΩ
1.275 18.8 kΩ
1.300 17.3 kΩ
1.325 16.0 kΩ
1.350 14.8 kΩ
1.375 13.8 kΩ
1.400 12.8 kΩ
1.425 12.0 kΩ
1.450 11.2 kΩ
1.475 10.5 kΩ
V
out
(Standard) R
set
(Pref’d Value) V
out
(Actual)
2.5 V 576 Ω 2.501V
2 V 3.09 kΩ 2.003 V
1.8 V 4.87 kΩ 1.804 V
1.5 V 9.76 kΩ 1.504 V
1.2 V 24.3 kΩ 1.204 V
1 V 82.5 kΩ 1.002 V
0.9 V Open 0.9 V
Table 2-1; Preferred Values of R
set
for Standard Output Voltages
Table 2-2; Output Voltage Set-Point Resistor Values
V
a
Req’dR
set
V
a
Req’dR
set
1.50 9.86 kΩ
1.55 8.72 kΩ
1.60 7.74 kΩ
1.65 6.89 kΩ
1.70 6.15 kΩ
1.75 5.49 kΩ
1.80 4.91 kΩ
1.85 4.39 kΩ
1.90 3.92 kΩ
1.95 3.50 kΩ
2.00 3.11 kΩ
2.05 2.76 kΩ
2.10 2.44 kΩ
2.15 2.14 kΩ
2.20 1.86 kΩ
2.25 1.61 kΩ
2.30 1.37 kΩ
2.35 1.15 kΩ
2.40 950 Ω
2.45 758 Ω
2.50 579 Ω
PTH03000W
V
IN
1
4
5
2
3
C
IN
100µF
(Required)
+
C
OUT
100µF
(Optional)
+
Inhibit
GND
GND
V
OUT
R
SET
0.1 W, 1 %
V
O
Adj
GNDInhibit
V
IN
V
O