DESCRIPTION

This device typically drives a direct current motor

servomechanism providing two extreme end posi-

tions and replaces end position switches or sen-

sors.

For more details see the Timing diagram (Fig. 1)

and the Application diagram (Fig. 2)

When the power supply is applied, or its polarity

is inverted the motor is powered up (start point).

The current of the motor reaches the start up

value near to the stall current, always higher than

and the consequent decrease of the current.

During the free running phase, the current in the

When the motor reaches the end of the run limit,

the current increases reaching a value that, de-

pending on the application, can be the stall value

or can depend on some torque limiting friction

(end point). Provided that this value is higher the

low consumption standby status, ready to restart

the motor for a new cycle if the polarity of the

power supply is inverted (or power is switched off

and on).

In any case, if the current exceeds the higher

also permits the motor to overcome some small

obstacle during the free run.

obtained by comparing the voltage on an external

voltage because in most applications, the end of

run current is depending only on motor and the

mechanic torque limiting device (friction current).

The threshold current for the short circuit detec-

tion is:

and depends intentionally on the supply voltage

because of the same dependence of the stall cur-

obtained by the following expression :

The block diagram is shown on the first page.

The change of the polarity between pins COM-

MON and LIVE, needs the active bridge to supply

the internal circuit. The internal supply voltage is

available between pins V+ and GND and a stor-

age and filter capacitor (100nF) must be con-

nected between these pins. The output stage

ELECTRICAL CHARACTERISTICS (Refer to the test circuit, unless otherwise specified.)

Symbol

Parameter

Test Condition

Min.

Typ.

Max.

Unit

Power supply

8

17

V

Quiescent current

Stanby

100

200

µA

Current ref. threshold for start

and end current (note 1)

70

100

135

µA

Current ref. threshold for short

circuit current det (note 2)

Vbat = 8V

240

300

400

300

440

550

400

560

690

µA

Current short circuit limit

8

A

Short circuit time delay

100

µs

0.6

1

Ohm

0.7

Ohm

Open load detector max. load

resistance

200

Ohm

Delay constant (note 3)

1

Deb

Immunity debouncer switch

=

R_ref

=

R_ref

= In 









⋅ Rex ⋅ Cex = Rex ⋅ Cex ⋅ Ktd

L9639

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