PT6650 Datasheet, PDF (3/5 Pages) Texas Instruments – 5 AMP 24V INPUT INTEGRATED SWITCHING REGULATOR

Application Notes
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PT6650 Series
More Application Notes
Adjusting the Output Voltage of the
PT6650 5Amp 24V Bus Converter Series
The output voltage of the Power Trends PT6650 Series ISRs
may be adjusted higher or lower than the factory trimmed pre-
set voltage with the addition of a single external resistor. Table 1
accordingly gives the allowable adjustment range for each model
in the series as V_a (min) and V_a (max).
Adjust Up: An increase in the output voltage is obtained by
adding a resistor R2, between pin 14 (V_o adjust) and pins 7-10
(GND).
Adjust Down: Add a resistor (R1), between pin 14 (V_o adjust)
and pins 11-13 (V_out).
Refer to Figure 1 and Table 2 for both the placement and value
of the required resistor, either (R1) or R2 as appropriate.
Notes:
1. Use only a single 1% resistorin either the (R1) or R2 loca-
tion. Place the resistor as close to the ISR as possible.
2. Never connect capacitors from V_o adjust to either GND,
V_out, or the Remote Sense pin. Any capacitance added to
the V_o adjust pin will affect the stability of the ISR.
3. If the Remote Sense feature is being used, connecting the
resistor (R1) between pin 14 (V_o adjust) and pin 1 (Remote
Sense) can benefit load regulation.
4. The minimum input voltage required by the part is V_out + 3,
or 9V, whichever is higher.
5. For output voltages above 12.5Vdc, the maximum output
current must be limited to 4Adc.
Figure 1
1
Vsense
Vin
4,5,6
Vin
PT6650
11,12,13
Vo
C _in
+
100 µF
STBY
3
GND
Vo(adj)
7,8,9,10
14 _(R1)
Adj Down
C _out
+
330 µF
R2
Adjust Up
COM
Vo
L
O
A
D
COM
The values of (R1) [adjust down], and R2 [adjust up], can
also be calculated using the following formulae.
(R1)
=
R_o (V_o – 1.25)(V_a – 1.25)
1.25 (V_o – V_a)
– R_s
kΩ
R2
=
R_o (V_o – 1.25)
V_a - V_o
– R_s
kΩ
Where: V_o = Original output voltage
V_a = Adjusted output voltage
R_o = The resistance value in Table 1
R_s = The series resistance from Table 1
Table 1
PT6650 ADJUSTMENT AND FORMULA PARAMETERS
Series Pt #
PT6652
PT6651
Vo (nom)
2.5V
3.3V
Va (min)
1.8V
2.2V
Va (max)
4.3V
4.7V
Ro (kΩ)
4.99
4.22
Rs (kΩ)
2.49
4.99
PT6653
5.0V
3.0V
6.5V
2.49
4.99
PT6654
9.0V
6.0V
10.2V
2.0
12.7
PT6656
12.0V
9.0V
13.6V
2.0
12.7
PT6655
15.0V
10.0V
17.0V
2.0
12.7
Power Trends, Inc. 27715 Diehl Road, Warrenville, IL 60555 [phone] Fax: [phone] http://www.powertrends.com
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