A5303 Standard 3 V Smoke Detector IC

By Allegro MicroSystems, LLC 130

A5303 Standard 3 V Smoke Detector IC

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.

  • Low average standby current allows 10-year battery life
  • Digital filter on I/O provides significant noise immunity
  • Timer (hush) mode for enabling reduced sensitivity period
  • Logic outputs to control an external sound IC
  • Latching alarm indicator identifies alarm-initiating devices
  • Temporal horn pattern, per UL217, NFPA72, ISO8201
  • Triple horn-chip to distinguish chamber warning 
  • Power-on reset (POR)
  • 2.3 V to 5.5 V operating range
  • Interconnect option
  • Built-in circuits to reduce false triggering
  • ESD protection circuitry on all pins
  • Chamber sensitivity test and warning
  • Low battery detection and warning

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