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APPLICATION INFORMATION

Adjusting the Output Voltage of the PTH04000W Wide-Output Adjust Power Modules

R

SET =10k

x

W

0.891 V

V -0.9V

O

-3.24kW

VI

GND

GND

1

5

6

3

4

2

Track

VI

VO

VO

GND

Inhibit

V Adj

O

C

47 F

(Required)

I

µ

PTH04000W

C

47 F

(Optional)

O

µ

R

0.05W

1%

SET

PTH04000W

SLTS247B – JUNE 2005 – REVISED OCTOBER 2007

The VO Adjust control (pin 5) sets the output voltage of the PTH04000W product. The adjustment range is from

0.9 V to 3.6 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

RSET

VO

(Required)

(Standard Value)

(Actual)

3.3 V (1)

475

Ω

3.298 V

2.5 V (1)

2.32 k

Ω

2.502 V

2 V

4.87 k

Ω

1.999 V

1.8 V

6.65 k

Ω

1.801 V

1.5 V

11.5 k

Ω

1.504 V

1.2 V

26.1 k

Ω

1.204 V

1 V

84.5 k

Ω

1.001 V

0.9 V

Open

0.9 V

(1)

The minimum input voltage is 3 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 © 2005–2007, Texas Instruments Incorporated

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