By Allegro MicroSystems, LLC 61
Allegro MicroSystems' A5303 is a low-current BiCMOS photoelectric smoke detector circuit with ultra-low standby current, which allows an average 10-year battery life. This device can be used with an infrared optical chamber to sense light scattered from smoke particles. A networking capability allows units to be interconnected so that if any unit senses smoke, all units will sound an alarm.
A variable-gain photoamplifier can be directly interfaced to an infrared emitter-detector pair. The amplifier gain levels are determined by two external capacitors and are internally selected depending on the operating mode. The internal oscillator and timing circuitry minimize standby power by sensing for smoke for only 100 μs once every 10 seconds. A special three-stage-speedup sensing scheme is incorporated to minimize the time to an audible alarm and also reduce false triggering.