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Application Notes
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Adjusting the Output Voltage of the PTH05000W
Wide-Output Adjust Power Modules
The Vo Adjust control (pin 4) sets the output voltage of
the PTH05000Wproduct. The adjustment range is
from 0.9 V to 3.6 V. The adjustment method requires
the addition of a single external resistor, Rset, that must
be connected directly between the Vo 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.
Rset
= 10 k
0.891 V
– 3.24 k
Vout – 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 Vo Adjust to either GND or
Vout. Any capacitance added to the Vo Adjust pin will affect
the stability of the regulator.
0.900
Open
0.925
353 k
0.950
175 k
0.975
116 k
1.000
85.9 k
1.025
68.0 k
1.050
56.2 k
1.075
47.7 k
1.100
41.3 k
1.125
36.4 k
1.150
32.4 k
1.175
29.2 k
1.200
26.5 k
1.225
24.2 k
1.250
22.2 k
1.275
20.5 k
1.300
19.0 k
1.325
17.7 k
1.350
16.6 k
1.375
15.5 k
1.400
14.6 k
1.425
13.7 k
1.450
13.0 k
1.475
12.3 k
1.50
11.6 k
1.55
10.5 k
1.60
9.49 k
1.65
8.64 k
1.70
7.90 k
1.75
7.24 k
1.80
6.66 k
1.85
6.14 k
1.90
5.67 k
1.95
5.25 k
Vout (Standard)
Rset (Pref’d Value)
Vout (Actual)
3.3 V
475
3.298V
2.5 V
2.32 k
2.502 V
2 V
4.87 k
1.999 V
1.8 V
6.65 k
1.801 V
1.5 V
11.5 k
1.504 V
1.2 V
26.1 k
1.204 V
1 V
84.5 k
1.001 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
Va Req’dRset
2.00
4.86 k
2.05
4.51 k
2.10
4.19 k
2.15
3.89 k
2.20
3.61 k
2.25
3.36 k
2.30
3.12 k
2.35
2.90 k
2.40
2.70 k
2.45
2.51 k
2.50
2.33 k
2.55
2.16 k
2.60
2.00 k
2.65
1.85 k
2.70
1.71 k
2.75
1.58 k
2.80
1.45 k
2.85
1.33 k
2.90
1.22 k
2.95
1.11 k
3.00
1.00 k
3.05
904
3.10
810
3.15
720
3.20
634
3.25
551
3.30
473
3.35
397
3.40
324
3.45
254
3.50
187
3.55
122
3.60
60
PTH05000W
V
IN
1
4
5
2
3
C
IN
330F
(Required)
+
C
OUT
100F
(Optional)
+
Inhibit
GND
V
OUT
R
SET
0.1 W, 1 %
V
O Adj
GND
Inhibit
V
IN
V
O
PTH05000W