PT6680 Datasheet, PDF (3/6 Pages) Texas Instruments – 5 Amp 18-36V Input Integrated Switching Regulator

Application Notes
PT6680 Series
Adjusting the Output Voltage of the
PT6680 5Amp 18-36V Bus Converter Series
The output voltage of the Power Trends PT6680 Series
ISRs may be adjusted higher or lower than the factory
trimmed pre-set voltage with the addition of a single
external resistor ¹. Table 1 gives the respective 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 ad-
just) and pins 7-10 (GND).
Adjust Down:
Add a resistor (R1), between pin 14 (V_o
adjust) and pins 11-13 (V_out).
Figure 1
1
Vsense
Vin
4,5,6
Vin
PT6680
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
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 pin 14 (V_o adjust) and pin 1 (Remote
Sense) can benefit load regulation.
4. For output voltages above 10.0Vdc, the maximum output
current must be limited to 4Adc.
5. 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 18V,
whichever is higher.
V_in (max)
= (10 x V_out )V or 36V,
whichever is less.
Table 1
PT6680 ADJUSTMENT AND FORMULA PARAMETERS
Series Pt #
PT6682
PT6681
PT6683
Vo (nom)
2.5V
3.3V
5.0V
Va (min)
1.8V
2.2V
3.0V
Va (max)
4.3V
4.7V
6.5V
Ro (kΩ)
4.99
4.22
2.49
Rs (kΩ)
2.49
4.99
4.99
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 1
= The series resistance from Table 1
PT6684
9.0V
6.0V
10.2V
2.0
12.7
PT6686
12.0V
9.0V
13.6V
2.0
12.7
PT6685
15.0V
10.0V
17.0V
2.0
12.7
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