PT6120_08 Datasheet, PDF (3/7 Pages) Texas Instruments – Adjustable Output Voltage

Application Notes
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PT6100/6120/6210/6220/6300/6320 Series
More Application Notes
Adjusting the Output Voltage of Power Trends’
Wide Input Range Bus ISRs
The output voltage of the Power Trends’ Wide Input Range
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 for either 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 12 (V_o adjust) and pins 5-8
(GND).
Adjust Down: Add a resistor (R1), between pin 12 (V_o adjust)
and pins 9-11(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% resistor in 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 or
V_out. Any capacitance added to the V_o adjust pin will affect
the stability of the ISR.
4. Adjustments to the output voltage may place additional
limits on the maximum and minimum input voltage for the
part. The revised maximum and minimum input voltage
limits must comply with the following requirements. Note
that the minimum input voltage limits are also model depen-
dant.
V_in (max) = (8 x V_a)V or ^*30/38V,
whichever is less.
*_{Limit is 30V when inhibit function is active.}
PT6x0x/PT6x1x series:
V_in (min) = (V_a + 4)V or 9V,
whichever is greater.
PT6x2x series:
V_o <10V; V_in (min) = (V_a + 2.0)V or 7.0V,
whichever is greater.
V_o ≥10V; V_in (min) = (V_a + 2.5)V
Figure 1
Vin
C1
1µF Ceramic
(Optional)
PT6100/6200/6300
2,3,4
Vin
9,10,11
Vo
GND
Vo(adj)
5,6,7,8
12
(R1)
Adj Down
R2
Adjust Up
C2
+
100 µF
(Req'd)
COM
Vo
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
kΩ
R2
=
1.25 R_o
V_a – V_o
kΩ
Where: V_o = Original output voltage
V_a = Adjusted output voltage
R_o = The resistance value fromTable 1
Table 1
ISR ADJUSTMENT RANGE AND FORMULA PARAMETERS
1Adc Rated
PT6102
PT6122
PT6101
PT6121
2Adc Rated
PT6213
PT6223
PT6212
PT6222
3Adc Rated
PT6303
PT6323
PT6302
PT6322
Vo (nom)
3.3
Va (min)
1.89
Va (max)
6.07
Ro (kΩ)
66.5
5.0
5.0
1.88
2.18
11.25
8.5
150.0
90.9
PT6103
PT6214
PT6304
12.0
2.43
22.12
243.0
Power Trends, Inc. 27715 Diehl Road, Warrenville, IL 60555 [phone] Fax: [phone] http://www.powertrends.com
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