Application Notes

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

PT6400 Series

Adjusting the Output Voltage of the PT6400 Series

3AMP 5V Bus Converters

The output voltage of the Power Trends PT6400 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

and V

Adjust Up:

(See note 1) An increase in the output voltage

is obtained by adding a resistor R1, between pin 12 (V

o

adjust) and pins 9-11 (V

Adjust Down:

(See note 1) Add a resistor (R2), between

pin 12 (V

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

Notes:

1. The direction in which each resistor adjusts the

output of the PT6400 series differs from many other

Power Trends products. These output voltage

adjustment notes are therefore specific only to the

PT6400 models.

location. Place the resistor as close to the ISR as

possible.

3. Never connect capacitors from V

GND or V

Any capacitance added to the V

pin will affect the stability of the ISR.

4. An increase in the output voltage may place

additional limits on the input voltage range of the

part. The revised minimum input voltage will be

(V

Do not

exceed 5.5Vdc.

Figure 1

also be calculated using the following formulae.

R1

=

– 49.9

k

Ω

(R2)

=

Where:

V

o

= Original output voltage

V

a

= Adjusted output voltage

Table 1

PT6400 ADJUSTMENT RANGE

Series Pt #

PT6408

PT6404

PT6406

PT6407

PT6409

PT6405

Vo (nom)

1.2

1.5

1.8

2.1

2.5

3.3

Va (min)

1.1

1.3

1.5

1.8

2.1

2.8

Va (max)

1.4

1.8

2.2

2.6

3.1

3.8

R1

Adjust

Up

C1

100

µF

C2

100

µF

Vo

COM

COM

Vin

++

(R2)

Adj Down

PT6400

9,10,11

12

5,6,7,8

2,3,4

Vin

Vo

G N D

Vo(adj)