2543

PROTECTED

QUAD POWER DRIVER

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

TYPICAL OUTPUT BEHAVIOR

CIRCUIT DESCRIPTION AND APPLICATION

INCANDESCENT LAMP DRIVER

For incandescent lamp applications, the UDx2549B/EB or

UDx2559B/EB, with improved shortcircuit protection and thermal

limiting, are recommended.

INDUCTIVE LOAD DRIVER

Bifilar (unipolar) stepper motors, relays, or solenoids can be driven

directly. The internal flyback diodes prevent damage to the output

transistors by suppressing the high-voltage spikes that occur when

turning OFF an inductive load. For rapid current decay (fast turn-OFF

speeds), the use of Zener diodes will raise the flyback voltage and

improve performance. However, the peak voltage must not exceed the

≤ V

FAULT CONDITIONS

In the event of a shorted load, the load current will attempt to

increase. As described above, the drive current to the affected

output stage is diverted, causing the output stage to go linear, limiting

the peak output current to approximately 1 A. As the power dissipation

of that output stage increases, a thermal gradient sensing circuit will

become operational, further decreasing the drive current to the af-

fected output stage and reducing the output current to a value depen-

≈ 2.4/V

corrected, the output stage will return to its normal saturated condition.

Due to the independent operation of the four channels, only

a single channel should be shorted at a time. Multiple overload

conditions may be tolerated provided rated package power

dissipation is not exceeded.

NORMAL LOAD

TIME

Dwg. WP-013-1

NOT TO SCALE

CURRENT LIMIT (12 V SUPPLY)

SHORT CIRCUIT

CURRENT LIMIT (24 V SUPPLY)