2436

COUNTDOWN POWER TIMER

1 k

Ω

+

1

µF

1

2

3

4

5

6

7

8

VREG

F/F

BATTERY

10 k

Ω

16 V

TO

COURTESY

LIGHT

CIRCUIT DESCRIPTION

OSC. An external resistor in the range of

200 k

Ω to 2 MΩ and an external capacitor

in the range of 0.001

µF to 1 µF determine

the frequency of the internal oscillator. The

the overall output time period (after the

digital countdown) of

where t is in seconds. See also MODE

SELECT.

OUTPUT. The output is an open-collector

of a Darlington-connected transistor. The

output is ON (low) during the timing period.

An external Zener diode is used to protect

the output against inductive-load switching

transients and automotive “load dump”.

TOGGLE. A push-button, momentary-action

switch at this input toggles the timer from

the OFF to the ON state. The oscillator and

countdown circuitry are started on the rising

edge of the input pulse. Internal de-bounce

circuitry is included.

SUPPLY. The timer requires a supply current

applied to this pin through a current-limiting

shunt regulator provides a stable supply to

the device over wide supply voltage varia-

decoupling.

MODE SELECT. With MODE SELECT

connected to GROUND, the first activation

will run for the preset time delay. All activa-

tions after the first will time out at half of the

initial preset time. This sequence is reset

each time the supply is interrupted. With

MODE SELECT connected to SUPPLY

delay each time it is activated.

Dwg. No. ES-013

COURTESY LIGHT TIMER

Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the

detail specifications as may be required to permit improvements in the design of its products.

Components made under military approvals will be in accordance with the approval requirements.

The information included herein is believed to be accurate and reliable. However, Allegro

MicroSystems, Inc. assumes no responsibility for its use; nor for any infringements of patents or other

rights of third parties which may result from its use.