APPLICATION INFORMATION

ADJUSTING THE OUTPUT VOLTAGE

PTH12020x

14

5

6

GND

GN D

10

9

8

7

GND

VO Sense

VOUT

VO Adj

RSET, 1%

VO Sense

VOUT

COUT

330 mF

Equation 1. Output Voltage Adjust

Rset + 10 kW

0.8 V

Vout * Vmin

* Rs kW

(1)

PTH12020W/L

SLTS208I – MAY 2003 – REVISED MARCH 2009 ............................................................................................................................................................. www.ti.com

The VOAdjust control (pin 4) sets the output voltage of the PTH12020W/L. The adjustment range is from 1.2 V 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 value of the required

resistor can either be calculated using Equation 1, or simply selected from the range of values given in Table 3.

Figure 11 shows the placement of the required resistor.

Table 1. Standard Values of Rset for Standard Output Voltages

PTH12020W

PTH12020L

VO(V)

VO(V)

VO(V)

RSET (kΩ)

RSET (kΩ)

(Req'd)

(Actual)

(Actual)

5 V

0.280

5.009

N/A

N/A

3.3 V

2.0

3.294

N/A

N/A

2.5 V

4.32

2.503

N/A

N/A

2 V

8.06

2.010

N/A

N/A

1.8 V

11.5

1.801

0.130

1.800

1.5 V

24.3

1.506

3.57

1.499

1.2 V

Open

1.200

12.1

1.201

1.1 V

N/A

N/A

18.7

1.101

1.0 V

N/A

N/A

32.4

0.999

0.9 V

N/A

N/A

71.5

0.901

0.8 V

N/A

N/A

Open

0.800

(1)

Use a 0.05-W, 1% tolerance with temperature stability of 100 ppm/°C (or better) for Rset. Place the resistor directly

between pins 4 and 7 using dedicated PCB traces.

(2)

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

the stability of the regulator.

Figure 11. Vo Adjust Resistor Placement

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

Table 2. Adjust Equation Parameters

PARAMETER

PTH12020W

PTH12020L

V(MIN)

1.2 V

0.8 V

RS

1.82 k

Ω

7.87 k

Ω

8

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