APPLICATION INFORMATION

ADJUSTING THE OUTPUT VOLTAGE

NOTES

Equation 1. Output Voltage Adjust

R

=10k

x

SET

W

0.8V

-R

k

S

W

V

-V

O

min

(1)

PTH12030W/L

SLTS211H – MAY 2003 – REVISED DECEMBER 2008 .................................................................................................................................................... www.ti.com

The VOAdjust control (pin 5) sets the output voltage of the PTH12030W/L. The adjustment range is 1.2V to 5.5V

for the W-suffix modules, and 0.8V to 1.8V for L-suffix modules. The adjustment method requires the addition of

a single external resistor, RSET, that must be connected directly between the VOAdjust and GND pins

(1). Table 1

gives the standard 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 required resistor can either be

calculated using Equation 1, or simply selected from the range of values given in Table 3. Figure 10 shows the

placement of the required resistor.

Table 1. Standard Values of RSET for Standard Output Voltages

PTH12030W

PTH12030L

VO (Required) (V)

RSET (kΩ)

VO (Actual) (V)

RSET(kΩ)

VO (Actual) (V)

5

0.280

5.009

N/A

N/A

3.3

2

3.294

N/A

N/A

2.5

4.32

2.503

N/A

N/A

2

8.06

2.01

N/A

N/A

1.8

11.5

1.801

0.130

1.8

1.5

24.3

1.506

3.57

1.499

1.2

Open

1.2

12.1

1.201

1.1

N/A

N/A

18.7

1.101

1

N/A

N/A

32.4

0.999

0.9

N/A

N/A

71.5

0.901

0.8

N/A

N/A

Open

0.8

Figure 10. Vo Adjust Resistor Placement

1. RSET: Use a 0.05 W resistor with a tolerance of 1% and temperature stability of 100 ppm/C (or better).

Connect the resistor directly between pins 5 and 7, as close to the regulator as possible, using dedicated

PCB traces.

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

affects the stability of the regulator.

Use Equation 1 to calculate the adjust resistor value. See Table 2 for parameters, RS and Vmin.

Table 2. Adjust Equation Parameters

PARAMETERS

PTH12030W

PTH12030L

V(MIN)

1.2 V

0.8 V

V(MAX)

5.5 V

1.8 V

RS

1.82 k

Ω

7.87 k

Ω

8

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