PT4313 datasheet(7/9 Pages) TI

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Application Notes

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(R1)

Adj Down

Adjust Up

(R3)

31.6k

Ω

(VR1), 5.1V

MM3Z5V1

–V

PT4310

1 ( + )

+Vin

-Vin

±Vo

Adjust

COM

Remote

On/Off

2 ( – )

Note: (R3) and (VR1) are only

required with (R1), for adjusting

the output down.

PT4310 Series

Adjusting the Output Voltage of the PT4310

Series of Isolated DC/DC Converters

The PT4310 is a series of 6-watt isolated dual-output

DC/DC converters. The PT4310 series is functionally

similar and pin-compatible with the former PT4300 series,

but the adjustment of the output voltages is different 1.

The ±Vo output voltages of the PT4310 series may be

adjusted higher or lower than the factory trimmed value.

The adjustment method uses a single external resistor to

adjust the magnitude of both output voltages by as much

as ±5%. When adjusting the output voltages to a lower

value, an external bias voltage, referenced to the –Vin

(primary), is also required. 2

Figure 1-1 gives a suggested schematic for the PT4310

output voltage adjustment. The components (R3) and

(VR1) are only required with (R1). 3

Adjust Up:

Add a resistor, R2, between Vo Adjust (pin 12)

and –Vin (pin 17).

Adjust Down:

An increase in the ±Vout output voltages is

obtained by adding a resistor, (R1), between Vo Adjust

(pin 12) and a +5 VDC external voltage source. The

voltage source must be referenced to –Vin (pin 17). A

simple external voltage source may be implemented by

adding the components (R3) and (VR1) in Figure 1-1.

Refer to Table 1-1 for the value of the external adjust

resistors, R2, or (R1) required to adjust each model of the

PT4310 series, up or down respectively by the stated

percentage. See Figure 1-1 for the placement of (R1),

R2, and other components.

DC/DC CONVERTER ADJUSTMENT RESISTOR VALUES

Series Pt #

PT4311

PT4313

PT4314

Vo (nom)

±5 V

±12 V

±24 V

(Io1+|Io2|)max 4

1.2 A

0.5 A

0.25 mA

|±Vo|% Adjust

–5.0%

(90.9 k

Ω)

(0 k

Ω)

(220 k

Ω)

–2.5%

(750 k

Ω)

(511 k

Ω)

(950 k

Ω)

0.0%

+2.5%

750 k

Ω

511 k

Ω

950 k

Ω

+5.0%

90.9 k

Ω

0 k

Ω

220 k

Ω

R1 = (Blue)

R2 =Black

Figure 1-1

Table 1-1

Notes

1. In most stand-alone applications the PT4310 series is a

direct substitute for the PT4300 series. However, the

method of output voltage adjustment differs between

the two series. For existing applications that use a

PT4300 part, a modification to the circuit will be

necessary if the output voltage is required to be

adjusted to a value other than the pre-trimmed factory

setting.

2. The adjustment control input, Vo Adjust (pin 12) is

referenced to –Vin (pin 17).

3. (R3) and (VR1) provide a +5 VDC external bias voltage

that is required for (R1) to adjust the output voltages

down. If the outputs are to be adjusted up, only the R2

is required.

4. The PT4310 series is rated for 6 watts total output.

An increase in the output voltage will require a

corresponding reduction in the maximum allowed

total output current (Io1 +Io2) max in Table 1-1.

The total current from both outputs must comply

with the following equation:-

Io1 +Io2 =

Adc

or (Io1 +Io2)max,

whichever is less.

Where,

Va = the new (adjusted) output voltage.

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