PHOTOELECTRIC SMOKE DETECTOR

WITH INTERCONNECT AND TIMER

The A5358CA is a low-current BiCMOS circuit providing all of the

required features for a photoelectric type smoke detector. This device

can be used in conjunction with an infrared photoelectric chamber to

sense scattered light from smoke particles. Special features are

incorporated in the design to facilitate calibration and testing of the

finished detector. The device is designed to comply with Underwriters

Laboratories Specification UL217 and British Standard BS 5446,

Part 1.

A variable-gain photo amplifier can be directly interfaced to an

infrared emitter/detector pair. The amplifier gain levels are determined

by two external capacitors that are then internally selected depending

on the operating mode. Low gain is selected during standby and timer

modes. During a local alarm this low gain is increased (internally) by

~10% to reduce false triggering. High gain is used during the push-

button test and during standby to periodically monitor the chamber

sensitivity.

The internal oscillator and timing circuitry keeps standby power to

a minimum by sensing for smoke every 10 seconds in a 10

µs window.

A special three-stage speedup sensing scheme is incorporated to

minimize the time to an audible alarm and also to reduce false trigger-

ing. Also, two consecutive cycles of degraded chamber sensitivity are

required for a warning signal to occur.

The A5358CA is supplied in a low-cost 16-pin dual in-line plastic

package. It is rated for continuous operation over the temperature

range of -25

°C to +75°C.

1

2

3

4

5

6

7

89

10

11

12

13

14

15

16

OSC. &

TIMING

HORN

DRIVER

TEST

DETECT

HUSH

OSC. CAP.

HORN

HORN

– SUPPLY

C

I / O

C

STROBE

+ SUPPLY

TIMING RES.

FEEDBACK

1

2

LED

IRED

LOGIC

1

2

Dwg. PC-007

ABSOLUTE MAXIMUM RATINGS

Supply Voltage Range,

Input Voltage Range,

Operating Temperature Range,

Storage Temperature Range,

CAUTION: CMOS devices have input static

protection but are susceptible to damage if exposed

to extremely high static electrical charges.

Always order by complete part number: A5358CA .

FEATURES

s Interconnect Up to 50 Detectors

s Piezoelectric Horn Driver

s All Internal Low-Battery Detection

s Power-ON Reset

s Internal Timer & Control for Reduced Sensitivity

s Built-In Circuits to Reduce False Triggering

s 6 V to 12 V Operating Voltage Range

s ESD-Protection Circuitry on All Pins

5358