Application Notes

For technical support and further information visit http://power.ti.com

PTH03000W

Adjusting the Output Voltage of the PTH03000W

Wide-Output Adjust Power Modules

The Vo Adjust control (pin 4) sets the output voltage of

the PTH03000Wproduct. The adjustment range is

from 0.9 V to 2.5 V. The adjustment method requires

the addition of a single external resistor, Rset, that must

be connected directly between the Vo Adjust and GND

pins 1. Table 2-1 gives the preferred value of the external

resistor for a number of standard voltages, along with the

actual output voltage that this resistance value provides.

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 2-2.

Figure 2-1 shows the placement of the required resistor.

Rset

= 10 k

Ω ·

0.891 V

– 4.99 k

Ω

Vout – 0.9 V

Figure 2-1; V

o

Adjust Resistor Placement

Notes:

1. Use a 0.1 W resistor. 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 4 and 1

using dedicated PCB traces.

2. Never connect capacitors from Vo Adjust to either GND or

Vout. Any capacitance added to the Vo Adjust pin will affect

the stability of the regulator.

0.900

Open

0.92535

1 k

Ω

0.950

173 k

Ω

0.975114 k

Ω

1.000

84.1 k

Ω

1.02566.3 k

Ω

1.050

54.4 k

Ω

1.07545

.9 k

Ω

1.100

39.6 k

Ω

1.12534.6 k

Ω

1.150

30.7 k

Ω

1.17527.4 k

Ω

1.200

24.7 k

Ω

1.22522.4 k

Ω

1.250

20.5 k

Ω

1.27518.8 k

Ω

1.300

17.3 k

Ω

1.32516.0 k

Ω

1.350

14.8 k

Ω

1.37513.8 k

Ω

1.400

12.8 k

Ω

1.42512.0 k

Ω

1.450

11.2 k

Ω

1.47510.5

k

Ω

Vout (Standard)

Rset (Pref’d Value)

Vout (Actual)

2.5 V

576

Ω

2.501V

2 V

3.09 k

Ω

2.003 V

1.8 V

4.87 k

Ω

1.804 V

1.5 V

9.76 k

Ω

1.504 V

1.2 V

24.3 k

Ω

1.204 V

1 V

82.5 k

Ω

1.002 V

0.9 V

Open

0.9 V

Table 2-1; Preferred Values of R

set

for Standard Output Voltages

Table 2-2; Output Voltage Set-Point Resistor Values

Va Req’dRset

Va Req’dRset

1.50

9.86 k

Ω

1.55

8.72 k

Ω

1.60

7.74 k

Ω

1.656.89 k

Ω

1.70

6.15 k

Ω

1.755

.49 k

Ω

1.80

4.91 k

Ω

1.854.39 k

Ω

1.90

3.92 k

Ω

1.953.5

0 k

Ω

2.00

3.11 k

Ω

2.052.76 k

Ω

2.10

2.44 k

Ω

2.152.14 k

Ω

2.20

1.86 k

Ω

2.251.61 k

Ω

2.30

1.37 k

Ω

2.351.15

k

Ω

2.40

950

Ω

2.4575

8

Ω

2.50

579

Ω

PTH03000W

V

IN

1

4

5

2

3

C

IN

100µF

(Required)

C

OUT

100µF

(Optional)

Inhibit

GND

GND

V

OUT

R

SET

0.1 W, 1 %

V

O Adj

GND

Inhibit

V

IN

V

O