Application Notes

For technical support and more information, see inside back cover or visit www.ti.com/powertrends

PT6670 Series

Adjusting the Output Voltage of the PT6670

Series Boost Voltage ISR

The Power Trends PT6670 ISRs are a series of convert-

ers that operate from a 3.3V or 5V input bus voltage. In

each case, the output voltage can be adjusted higher or

lower than the factory trimmed pre-set voltage. Adjust-

ment requires the addition of a single external resistor.

Table 1 gives the permissible adjustment range for each

model in the series as V

Adjust Up:

To increase the output, add a resistor

R2 between pin 14 (V

Adjust Down:

Add a resistor (R1), between pin 14

(V

Refer to Figure 1 and Table 2 for both the placement and value

of the required resistor.

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. Do not exceed the maximum advised adjustment voltage.

Doing so could over stress the part.

3. Never connect capacitors to the V

capacitance added to this pin will affect the stability of the

ISR.

4. In the case of the PT6671, when the output is adjusted

lower than the pre-trimmed output, the maximum input

voltage to the ISR should not exceed (V

The adjust up and adjust down resistor values can also be

calculated using the following formulas. Be sure to select

the correct formula parameters from Table 1 for the model

being adjusted.

(R1)

=

R2

=

Where:

Table 1

PT6670 ADJUSTMENT RANGE AND FORMULA PARAMETERS

Series Pt #

3.3V Bus

PT6671

PT6672

PT6673

5.0V Bus

PT6675

PT6674

Vo(nom)

5.0V

9.0V

12.0V

Va(min)

3.8V

8.2V

9.6V

Va(max)

5.5V

9.2V

12.8V

Ko (V·k

Ω

Ω

Ω

Ω

Ω)

25.0

48.75

47.41

Rs (k

Ω

Ω

Ω

Ω

Ω)

4.99

80.6

54.9

Figure 1

PT6670

11,12,13

14

7,8,9,10

4,5,6

Vin

V o

G N D

Vo(adj)

Vsense

1

C

out

+

C

in

+

L

O

A

D

(R1)

Adj Down

R2

Adjust

Up

Vin

COM

COM

Vo

R2 = Black

Table 2

PT6670 ADJUSTMENT RESISTOR VALUES

Series Pt #

3.3V Bus

PT6671

PT6672

PT6673

5.0V Bus

PT6675

PT6674

Vo(nom)

5.0V

9.0V

12.0V

Va(req’d)

Va(req’d)

3.8

(5.8)k

Ω

8.2

(58.3)k

Ω

3.9

(7.7)k

Ω

8.4

(111.0)k

Ω

4.0

(10.0k

Ω

8.6

(217.0)k

Ω

4.1

(12.8)k

Ω

8.8

(534.0)k

Ω

4.2

(16.3)k

Ω

9.0

4.3

(20.7)k

Ω

9.2

163.0k

Ω

4.4

(26.7)k

Ω

9.4

4.5

(35.0)k

Ω

9.6

(1.2)k

Ω

4.6

(47.5)k

Ω

9.8

(8.0)k

Ω

4.7

(68.3)k

Ω

10.0

(16.2)k

Ω

4.8

(110.0)k

Ω

10.2

(26.2)k

Ω

4.9

(235.0)k

Ω

10.4

(38.7)k

Ω

5.0

10.6

(54.8)k

Ω

5.1

245.0k

Ω

10.8

(76.3)k

Ω

5.2

120.0k

Ω

11.0

(106.0)k

Ω

5.3

78.3k

Ω

11.2

(151.0)k

Ω

5.4

57.5k

Ω

11.4

(226.0)k

Ω

5.5

45.0k

Ω

11.6

(376.0)k

Ω

11.8

(827.0)k

Ω

12.0

12.2

182.0k

Ω

12.4

63.3k

Ω

12.6

24.1k

Ω

12.8

4.4k

Ω