Date: 14/07/2010

BiCMOS photoelectric smoke detector from Allegro with a battery life of 10 years

Allegro has unveiled the A5303, a low-current BiCMOS photoelectric smoke detector circuit which Allegro claims has 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. This new device is targeted at the consumer smoke alarm market.

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 and are 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 approximately 45% to provide hysteresis. High gain is used during pushbutton test and to periodically monitor the chamber sensitivity during standby. The internal oscillator and timing circuitry minimize standby power by sensing for smoke for only 100 µs once every 10 s. A special three-stage-speedup sensing scheme is incorporated to minimize the time to an audible alarm and also to reduce false triggering. Chamber sensitivity is periodically monitored and two consecutive cycles of degraded sensitivity are required for a warning signal to occur. It has a thin profile of less than 1.2mm

Package: 20-pin TSSOP package (0.65 mm nominal lead pitch). The package is lead (Pb) free with 100% matte tin leadframe plating.

Availability: Now

For more information visit: www.allegromicro.com