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APPLICATION INFORMATION

Adjusting the Output Voltage of the PTH08000W Wide-Output Adjust Power Modules

R

=10k

x

SET

W

0.891 V

V -0.9V

O

-1.82kW

VI

GND

GND

VO

RSET

0.05W

1%

PTH08000W

1

5

6

2

3

4

V Adj

O

GND

Inhibit

VI

VO

C

100 F

(Required)

I

m

C

100 F

(Optional)

O

m

Track

PTH08000W

SLTS248B – JUNE 2005 – REVISED FEBRUARY 2008

The VO Adjust control (pin 5) sets the output voltage of the PTH08000W product. The adjustment range is from

0.9 V to 5.5 V. The adjustment method requires the addition of a single external resistor, RSET, that must be

connected directly between the VO Adjust and GND (pin 1). Table 1 gives the standard external resistor for a

number of common bus voltages, along with the actual voltage the resistance produces.

For other output voltages, the value of the required resistor can either be calculated using the following formula,

or simply selected from the range of values given in Table 2. Figure 9 shows the placement of the required

resistor.

Table 1. Standard Values of RSET for Common Output

Voltages

VO (V)

RSET (kΩ)

VO (V)

(Required)

(Standard Value)

(Actual)

5 (1)

0.348

5.010

3.3

1.87

3.315

2.5

3.74

2.503

2

6.19

2.012

1.8

8.06

1.802

1.5

13.0

1.501

1.2

27.4

1.205

1

86.6

1.001

0.9

Open

0.9

(1)

The minimum input voltage is 4.5 V or (VO + 1.1) V, whichever is

greater.

(1)

A 0.05-W rated resistor may be used. The tolerance should be 1%, with a temperature stability of 100 ppm/

°C (or

better). Place the resistor as close to the regulator as possible. Connect the resistor directly between pins 5 and 1

using dedicated PCB traces.

(2)

Never connect capacitors from VO Adjust to either GND or VO. Any capacitance added to the VO Adjust pin affects the

stability of the regulator.

Figure 9. VO Adjust Resistor Placement

Copyright © 2005–2008, Texas Instruments Incorporated

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