PT6620_14 Datasheet, PDF (3/19 Pages) Texas Instruments – Single Device: 6-A Output

Application Notes
PT6620 Series
Adjusting the Output Voltage of the
PT6620 6 A, 12-V Bus Converter Series
The output voltage of the Power Trends PT6620 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 V_o Adjust (pin 14) and
GND (pins 7-10).
Adjust Down: Add a resistor (R₁), between V_o Adjust (pin
14 ) and V_out (pins 11-13).
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% 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 V_o Adjust (pin 14) and Remote Sense
(pin 1) can benefit load regulation.
4. The minimum input voltage required by the part is
V_out + 3, or 9 V, whichever is higher.
Figure 1
1
Vsense
Vin
4,5,6
Vin
PT6620
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_a – 1.25)
(V_o – V_a)
– R_s
kΩ
R₂
=
1.25 R_o
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 1
= The series resistance from Table 1
Table 1
PT6620 ADJUSTMENT AND FORMULA PARAMETERS
Series Pt #
PT6622
PT6623
Vo (nom)
Va (min)
Va (max)
Ro (kΩ)
Rs (kΩ)
1.5 V
1.4 V
2.7 V
4.99
2.49
2.5 V
1.9 V
3.7 V
10.0
4.99
PT6621
3.3 V
2.3 V
4.5 V
12.1
12.1
PT6624
3.6 V
2.5 V
4.8 V
12.1
12.1
PT6625
5V
2.9 V
6.5 V
16.2
12.1
PT6626
9.0 V
5.2 V
10 V
12.1
12.1
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