UDN2987-6 Ver la hoja de datos (PDF) - Allegro MicroSystems

Número de pieza

componentes Descripción

Fabricante

UDN2987-6

DABIC-5 8-Channel Source Driver with Overcurrent Protection

Allegro MicroSystems 

UDN2987x-6

DABIC-5 8-Channel Source Driver

with Overcurrent Protection

Applications Information and Circuit Description

As with all power integrated circuits, the UDN2987A-6 and

UDN2987LW-6 have a maximum allowable output current

rating. The 500 mA rating does not imply that operation at

that value is permitted or even obtainable. The channel out-

put current trip point is specified as –370 mA, minimum;

therefore, attempted operation at current levels greater

than –370 mA may cause a fault indication and channel

shut down. The device is tested at a maximum of –350 mA

and that is the recommended maximum output current

per driver. It provides protection for current overloads or

shorted loads up to 30 V.

All outputs are enabled by pulling the OE/¯R input high.

When OE/¯R is low or allowed to float (internal pull-down),

all outputs are inhibited and the latches are reset. Note that

the reset pulse duration (OE/¯R low) should be at least 1 μs.

This will ensure safe operation under attempted reset condi-

tions with a shorted load. The latches are also reset during

power-up, regardless of the state of the OE/¯R input.

The load current causes a small voltage drop across the

internal low-value sense resistor. This voltage is com-

pared to the voltage drop across a reference resistor with

a constant current. The two resistors are matched to elimi-

nate errors due to manufacturing tolerances or tempera-

ture effects. Each channel includes a comparator and its

own latch. An overcurrent fault (VSENSE > VREF) will set

the affected latch and shut down only that channel. All

other channels will continue to operate normally. The

latch includes a 1 μs blanking delay, tBLANK, to prevent

unwanted triggering due to crossover currents generated

when switching inductive loads. For an abrupt short circuit,

the blanking and output switching times will allow a brief,

permissable current in excess of the trip current before the

output driver is turned off.

A common thermal shut down disables all outputs if the

chip temperature exceeds 165°C. At thermal shut down,

all latches are reset. The outputs are disabled until the chip

cools down to approximately 150°C (thermal hysteresis).

In the event of an overcurrent condition on any channel, or

chip thermal shut down, the FAULT open-collector output

is pulled low (turned on).

Overcurrent Fault Sense Circuit

VS

To Fault Latch

VREF

Matched

VSENSE

SENSE

REF

IREF

ILOAD

Allegro MicroSystems, Inc.

7

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

Share Link: