Application Notes
PT6460 & PT6470 Series
Adjusting the Output Voltage of the PT6460 &
PT6470 ISR Series
The output voltage of the PT6460 (5-V input) and the
PT6470 (3.3-V input) series of power modules may be
adjusted higher or lower than the pre-set voltage. The
adjustment method requires a single external resistor.
The value of the resistor can either be calculated using
the formulas given below, or simply selected from the
range of values given in Table 3-2. Table 3-1 gives the
allowable adjustment range for each model as Va (min)
and Va (max). Refer to Figure 3-1 for the placement of
the required resistor. Resistor R1 adjusts the output voltage
up, and the resistor (R2) adjusts it down.
The values of (R1) [adjust down], and R2 [adjust up],
can be calculated using the following formulas. Refer to
Figure 3-1 for the placement of the required resistor;
either (R1) or R2 as appropriate.
Ro (Va – 0.8)
(R1)
=
=
– Rs
– Rs
kΩ
kΩ
Vo – Va
0.8 Ro
Va – Vo
R2
Where:
V
V
a
= Original output voltage
= Adjusted output voltage
o
Adjust Up: An increase in the output voltage is obtained
by adding a resistor R2, between Vo Adjust (pin 12) and
GND (pin 5).
Ro = The resistance value from Table 3-1
Rs = The series resistance from Table 3-1
Notes:
Adjust Down: Add a resistor (R1), between Vo Adjust (pin 12)
and +Vsense (pin 11).
1. Use a 1 % (or better) tolerance resistor in either the (R1)
or R2 location. Place the resistor as close to the ISR as
possible.
Figure 3-1
2. Never connect capacitors from Vo adj to either GND or
Vout. Any capacitance added to the Vo adjust pin will affect
the stability of the ISR.
11
+Vsense
3. If the remote sense feature is not being used, the adjust
+VIN
+VO
2–4
9–10
Vin
Vout
PT6460/70
resistor (R1) can also be connected to Vout, (pins 9–10)
instead of +Vsense
.
Inhibit*
1
GND
Vo(adj)
12
5–8
4. The PT6472 may not be adjusted higher than the
nominal output voltage of 2.5 V. There is insuf ficient
input voltage to allow for any increase in output voltage.
(R1)
Adj Down
CIN
560 µF
(Req'd)
COUT
330 µF
(Optional)
+
+
R2
Adjust Up
COM
COM
Table 3-1
ISR OUTPUT VOLTAGE ADJUSTMENT RANGE AND FORMULA PARAMETERS
Series Pt. Nos.
5-V Bus:
PT6461
N/A
PT6462
PT6472
PT6463
PT6473
PT6464
PT6474
PT6465
PT6475
PT6466
PT6476
PT6467
PT6477
3.3-V Bus:
V
o
V
a
V
a
R
o
R
s
(nom)
(min)
(max)
(kΩ)
3.3 V
2.6 V
3.63 V
10.2
2.5 V
2.0 V
2.8 V *
10.7
2.0 V
1.66 V
2.32 V
10.0
1.8 V
1.52 V
2.1 V
10.2
1.5 V
1.31 V
1.82 V
9.76
1.2 V
1.1 V
1.52 V
10.0
1 V
0.95 V
1.32 V
10.2
(kΩ)
24.9
24.9
24.9
24.9
24.9
24.9
24.9
* The PT6472 may not be adjusted higher than its nominal output voltage of 2.5 V. See note 4
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