PT6470 Datasheet, PDF (7/14 Pages) Texas Instruments – 14-A 3.3-V Input Adjustable Integrated Switching Regulator

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 V_a (min)
and V_a (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.
Adjust Up: An increase in the output voltage is obtained
by adding a resistor R₂, between V_o Adjust (pin 12) and
GND (pin 5).
Adjust Down: Add a resistor (R₁), between V_o Adjust (pin 12)
and +Vsense (pin 11).
Figure 3-1
+V_IN
2–4 _Vin
11
+Vsense
PT6460/70 Vout ^9–10
C_IN
+
560 µF
(Req'd)
Inhibit*
1
GND
5–8
Vo(adj)
12
(R₁)
Adj Down
COM
R₂
Adjust Up
+V_O
C_OUT
+
330 µF
(Optional)
COM
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.
(R₁)
=
R_o (V_a – 0.8)
V_o – V_a
– R_s kΩ
R₂
=
0.8 R_o
V_a – V_o
– R_s kΩ
Where:
V_o = Original output voltage
V_a = Adjusted output voltage
R_o = The resistance value from Table 3-1
R_s = The series resistance from Table 3-1
Notes:
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.
2. Never connect capacitors from V_o adj to either GND or
V_out. Any capacitance added to the V_o adjust pin will affect
the stability of the ISR.
3. If the remote sense feature is not being used, the adjust
resistor (R₁) can also be connected to V_out, (pins 9–10)
instead of +V_sense.
4. The PT6472 may not be adjusted higher than the
nominal output voltage of 2.5 V. There is insufficient
input voltage to allow for any increase in output voltage.
Table 3-1
ISR OUTPUT VOLTAGE ADJUSTMENT RANGE AND FORMULA PARAMETERS
Series Pt. Nos.
5-V Bus:
PT6461
PT6462
PT6463
PT6464
3.3-V Bus:
N/A
PT6472
PT6473
PT6474
Vo (nom)
Va (min)
Va (max)
Ro (kΩ)
Rs (kΩ)
3.3 V
2.6 V
3.63 V
10.2
24.9
2.5 V
2.0 V
2.8 V *
10.7
24.9
2.0 V
1.66 V
2.32 V
10.0
24.9
1.8 V
1.52 V
2.1 V
10.2
24.9
PT6465
PT6475
1.5 V
1.31 V
1.82 V
9.76
24.9
* The PT6472 may not be adjusted higher than its nominal output voltage of 2.5 V. See note 4
PT6466
PT6476
1.2 V
1.1 V
1.52 V
10.0
24.9
PT6467
PT6477
1V
0.95 V
1.32 V
10.2
24.9
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