PT6653E Datasheet, PDF (6/16 Pages) Texas Instruments – Single Device: 5-A Output Input Voltage Range: 9 V to 28 V 12 V / 24 V Input Compatible

Application Notes
PT6650 Series
Adjusting the Output Voltage of the
PT6650 5-A 24-V Bus Converter Series
The output voltage of the 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 3-1 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 adj) and pins
7-10 (GND).
Adjust Down: To decrease the output voltage, add a resis-
tor (R₁), between pin 14 (V_o adj) and pins 11-13 (V_out).
Refer to Figure 3-1 and Table 3-2 for both the placement and
value of the required resistor, either (R₁) or R₂ as appropriate.
Notes:
1. Use only a single 1 % 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 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 adj) and pin 1 (Remote
Sense) can benefit load regulation.
4. Adjustments to the output voltage may place additional
limits on the input voltage for the part. The revised limits
must comply with the following requirements.
V_in (min) = (V_out + 3) V or 9 V, whichever is higher.
V_in (max) = (10 x V_out ) V or 28 V, whichever is less.
5. For output voltages above 12.5 Vdc, the maximum output
current must be limited to 4 Adc.
Figure 3-1
1
Vsense
Vin
4,5,6
Vin
PT6650
11,12,13
Vo
+
C _in
STBY
3
GND
Vo(adj)
7,8,9,10
14 _(R1)
Adj Down
R2
Adjust
Up
COM
+
C _out
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
V_a
R_o
R_s
= Original output voltage
= Adjusted output voltage
= The resistance value in Table 3-1
= The series resistance from Table 3-1
Table 3-1
PT6650 ADJUSTMENT AND FORMULA PARAMETERS
Series Pt #
PT6652
PT6651
Vo (nom)
Va (min)
Va (max)
Ro (kΩ)
Rs (kΩ)
2.5 V
1.8 V
4.3 V
4.99
2.49
3.3 V
2.2 V
4.7 V
4.22
4.99
PT6653
5V
3V
6.5 V
2.49
4.99
PT6654
9V
6V
10.2 V
2
12.7
PT6656
12 V
9V
13.6 V
2
12.7
PT6655
15 V
10 V
17 V
2
12.7
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