2559 Ver la hoja de datos (PDF) - Allegro MicroSystems

Número de pieza

componentes Descripción

Fabricante

2559

Protected Quad Power Driver

Allegro MicroSystems 

2559

Protected Quad Power Driver

TYPICAL OUTPUT

CHARACTERISTIC

TYPICAL OUTPUT BEHAVIOR

CIRCUIT DESCRIPTION AND APPLICATION

INCANDESCENT LAMP DRIVER

High incandescent lamp turn-ON/in-rush currents can contribute to poor

lamp reliability and destroy semiconductor lamp drivers. Warming or current-

limiting resistors protect both driver and lamp but use significant power either

when the lamp is OFF or when the lamp is ON, respectively. Lamps with

steady-state current ratings up to 700 mA can be driven by these devices with-

out the need for warming (parallel) or current-limiting (series) resistors.

When an incandescent lamp is initially turned ON, the cold filament is

at minimum resistance and would normally allow a 10x to 12x in-rush cur-

rent. With these drivers, during turn-ON, the high in-rush current is sensed by

the internal low-value sense resistor. Drive current to the output stage is then

diverted by the shunting transistor, and the load current is momentarily limited

to approximately 1.0 A. During this short transition period, the output cur-

rent is reduced to a value dependent on supply voltage and filament resistance.

During lamp warmup, the filament resistance increases to its maximum value,

the output stage goes into saturation and applies maximum rated voltage to the

lamp.

INDUCTIVE LOAD DRIVER

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

rectly. 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 inprove performance. However, the peak

voltage must not exceed the specified minimum sustaining voltage (VSUPPLY +

VZ + VF VOUT(SUS)).

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 reduced, caus-

ing the output stage to go linear, limiting the peak output current to approxi-

mately 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 affected output stage and reducing the output current to a value

dependent on supply voltage and load resistance.

Continuous or multiple overload conditions causing the chip temperature

to reach approximately 165°C will result in an additional reduction in output

current to maintain a safe level.

If the fault condition is corrected, the output stage will return to its normal

saturated condition.

Allegro MicroSystems, Inc.

6

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Share Link: