SLTS034A datasheet(5/10 Pages) TI

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Application Notes

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

PT6500 Series

Adjusting the Output Voltage of the

PT6500 5V/3.3V Bus Converters

The output voltage of the Power Trends PT6500 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

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

adjust) and pins 11-13 (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

location. Place the resistor as close to the ISR as

possible.

2. Never connect capacitors from Vo adjust to either

GND, Vout, or the Remote Sense pin. Any

capacitance added to the Vo 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 (Vo

adjust) and pin 1 (Remote Sense) can benefit load

regulation.

4. The minimum input voltage required by the part is

Vout + 1.2 or Vin(min) from Table 1, whichever is

higher.

Figure 1

(R1)

Adj Down

Adjust

COM

Vin

COM

PT6500

11,12,13

7,8,9,10

4,5,6

out

GND

o(adj)

STBY

o(sense)

The values of (R1) [adjust down], and R2 [adjust up], can

also be calculated using the following formulae.

Ro (Va – 1.0)

(R1)

(Vo – Va)

– Rs kΩ

– Rs

kΩ

Va - Vo

Where: V

= Original output voltage

= Adjusted output voltage

= The resistance value in Table 1

= The series resistance from Table 1

Table 1

PT6500 ADJUSTMENT AND FORMULA PARAMETERS

Series Pt #

PT6505

PT6507

PT6502

PT6508

PT6506

PT6503

PT6501

PT6504

Vo (nom)

1.2

1.3

1.5

1.7

1.8

2.5

3.3

3.6

Va (min)

1.14

1.19

1.27

1.36

1.4

1.8

2.25

2.5

Va (max)

2.35

2.45

2.65

2.85

2.95

3.5

4.2

4.3

Ro (kΩ

Ω

Ω)

2.49

4.99

12.1

10.0

Rs (k

Ω

Ω)

2.0

4.22

12.1

Vin(min)

3.1

4.5

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