Rset + 10 kW

0.8 V

Vout * 0.8 V

* 2.49 kW

RSET

1%

0.05 W

PTH04040W

12

15

9

10 13

16

11

14

18

VO

VO

CO

+Sense

−Sense

GND

Track

Adjust

17

GND

GND

PTH04040W

www.ti.com

SLTS238C – SEPTEMBER 2005 – REVISED JUNE 2010

ADJUSTING THE OUTPUT VOLTAGE OF THE PTH04040W

The VO Adjust control (pin 17) sets the output voltage of the PTH04040W to a value higher than 0.8 V. The

adjustment range is from 0.8 V to 2.5 V. For an output voltage other than 0.8 V a single external resistor, RSET 1,

must be connected directly between the VO Adjust (pin 17) and the output GND (pin 16)

(2). Table 2 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 is calculated using the following formula, or by

selecting from the range of values given in Table 3. Figure 9 shows the placement of the required resistor.

(1)

Table 2. Preferred Values of Rset for Standard Output Voltages

VOUT (Standard)

(1)

RSET (Preferred Value)

VOUT (Actual)

2.5 V

2.21 k

Ω

2.502 V

2 V

4.12 k

Ω

2.010 V

1.8 V

5.49 k

Ω

1.803 V

1.5 V

8.87 k

Ω

1.504 V

1.2 V

17.4 k

Ω

1.202 V

1 V

36.5 k

Ω

1.005 V

0.8 V

Open

0.8 V

(1)

The nominal input voltage must be at least 2 × VO. Output voltage regulation is specified with an input voltage within ±10% from nominal

3.3 V or 5 V. For example, for VI = 5 V and VO = 2.5 V, the input can vary between 4.5 V and 5.5 V.

Figure 9. VO Adjust Resistor Placement

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