HTA20003R3SSLASHEM datasheet(8/14 Pages) IRF

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HTA-SERIES

Examination of the equation relating output voltage and

resistor value reveals a special benefit of the circuit topology

utilized for remote sensing of output voltage in the

HTA200XXS series of converters. It is apparent that as the

resistance increases, the output voltage approaches the

nominal set value of the device. In fact the calculated limiting

value of output voltage as the adjusting resistor becomes

very large, is

≈ 25mV above nominal device voltage.

The consequence is that if the +sense connection is

unintentionally broken, an HTA200XXS has a fail-safe output

voltage of Vout + 25mV, where the 25mV is independent of

the nominal output voltage. It can be further demonstrated

that in the event of both the +Sense and -Sense connections

being broken, the output will be limited to Vout + 440mV.

This 440mV is also essentially constant independent of the

nominal output voltage. While operation in this condition is

not damaging to the device, not all performance parameters

will be met.

Output Voltage Adjust - Dual Output Models

By use of the Trim pin (10), the magnitude of output voltages

can be adjusted over a limited range in either a positive or

negative direction. Connecting a resistor between the trim

pin and either the output return or the positive output will

raise or lower the magnitude of output voltages. The span

of output voltage adjustment is restricted to the limits shown

in Table I.

Fig V. Connection for V

OUT Adjustment

Connect R

ADJ to + to increase, - to decrease

Table 1. Output Voltage Trim Values and Limits

Note that the nominal magnitude of output voltage resides in

the middle of the table and the corresponding resistor value

is set to

∞. To set the magnitude greater than nominal, the

adjust resistor is connected to output return. To set the

magnitude less than nominal, the adjust resistor is

connected to the +Output. (Refer to Fig V.)

For output voltage settings that are within the limits, but

between those listed in Table I, it is suggested that the

resistor values be determined empirically by selection or by

use of a variable resistor. The determined value can then

be replaced with a good quality fixed resistor for permanent

installation.

When use of this adjust feature is elected, the user should

be aware that the temperature performance of the converter

output voltage will be affected by the temperature

performance of the resistor selected as the adjustment

element and therefore, is advised to employ resistors with a

very small temperature coefficient of resistance.

VOUT RADJ

VOUT

RADJ

VOUT

RADJ

5.5

12.5

15.5

5.4

12.5K

12.4

47.5K

15.4

62.5K

5.3

33.3K

12.3

127K

15.3

167K

5.2

75K

12.2

285K

15.2

375K

5.1

200K

12.1

760K

15.1

1.0M

5.0

∞

12.0

∞

15.0

∞

4.9

190K

11.7

975K

14.6

1.2M

4.8

65K

11.3

288K

14.0

325K

4.7

23K

10.8

72.9K

13.5

117K

4.6

2.5K

10.6

29.9K

13.0

12.5K

4.583

10.417

12.917

HTA20005D

HTA20012D

HTA20015D

N/C

Trim

N/C

- Output

Output Return

+ Output

Loads

RADJ

HTA200XXD

HTA20003R3S/EM Datasheet(PDF) 8 Page - International Rectifier

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