Application Notes

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

PT6420 Series

Adjusting the Output Voltage of the PT6420 Series

3AMP 5V Bus Converters

The output voltage of the Power Trends PT6420 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 14 (V

o

adjust) and pins 11-13 (V

Adjust Down:

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

pin 14 (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 PT6420 series differs from many other Power Trends

products. These output voltage adjustment notes are

therefore specific only to the PT6420 models.

location. Place the resistor as close to the ISR as possible.

3. Never connect capacitors from V

V

the V

4. The PT6420 incorporates a Remote Sense (See Figure 1).

If this feature is being used, connecting the resistor R1

between pin 14 (V

benefit load regulation.

5. 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

whichever is higher. Do not exceed 5.5Vdc.

Table 1

PT6420 ADJUSTMENT RANGE

Series Pt #

PT6428

PT6424

PT6426

PT6427

PT6429

PT6425

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)

1.41.8

2.2

2.6

3.1

3.8

Figure 1

R1

Adjust

Up

C1

100

µF

C2

100

µF

Vo

COM

COM

Vin

+

+

(R2)

Adj Down

L

O

A

D

PT6420

11,12,13

14

7,8,9,10

4,5,6

Vin

V o

G N D

Vo(adj)

1

Vsense

also be calculated using the following formulae.

R1

=

– 49.9

k

Ω

(R2)

=

Where:

V

o

= Original output voltage

V

a

= Adjusted output voltage