Allegro MicroSystems A5350CA-T

Overview

A5350CA-T from Allegro MicroSystems is a discontinued BiCMOS ionization smoke detector ASIC with integrated oscillator, active guard amplifiers, piezoelectric horn drivers, and interconnect capability for up to 125 units. It delivers ultra-low standby current (5.0 μA typ. at 9 V), operates from –10°C to 60°C, and uses a 16-pin DIP package with matte tin leadframe plating. It enables battery-powered residential/commercial smoke alarms with synchronized alarm propagation.

For engineers reviewing the A5350CA-T datasheet, A5350CA-T pinout, A5350CA-T application, or A5350CA-T equivalent, key selection considerations include its discontinued status, low-battery threshold adjustability via LOW-V SET, inverted alarm polarity on DETECT IN, and precise timing control via TIMING RES and OSC CAP pins for chamber-specific sensitivity calibration.

Technical Context

The A5350CA-T integrates a 1.67 s standby oscillator that powers the circuit for only 10 ms per cycle, enabling 5.0 μA typical supply current. Its dual active guard amplifiers (GUARD1/GUARD2) maintain ≤±100 mV offset versus DETECT IN to suppress surface leakage in ion chambers.

Alarm triggering requires V_DETECTIN > V_{SENSITIVITYSET}, with inverted polarity versus conventional ion detectors. Interconnect logic enforces a 93.9 ms minimum I/O high duration to prevent false alarms from noise, while local smoke detection initiates a 41.67 ms oscillator period and 160 ms horn on-time.

Key Specifications

Pinout & Package

Package: 16-pin plastic dual in-line package (DIP), Pb-free with 100% matte tin leadframe plating, rated for –10°C to 60°C continuous operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ionization smoke detector applications.

Compared with A5350CA-T, A5351CA-T offers direct replacement with higher ESD tolerance and ongoing production status, while SL18-125 demands significant board-level redesign but avoids obsolescence risk through discrete component sourcing.

Availability

A5350CA-T is available at Aetrix Electronics and suitable for residential smoke alarms, commercial building safety systems, and RV fire detection requiring stable component supply despite its discontinued status.

Supply support for A5350CA-T includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Allegro MicroSystems is a U.S.-based semiconductor company specializing in magnetic sensing, power ICs, and safety-critical analog solutions for automotive, industrial, and consumer markets.

The A5350 product line was designed specifically for ultra-low-power ionization smoke detection, integrating precision analog front-ends, timing control, and interconnect logic into a single BiCMOS ASIC.

FAQ

Is A5350CA-T still in production?

No, A5350CA-T is a discontinued product. Allegro MicroSystems classified it as "NOT FOR NEW DESIGN" effective May 4, 2009, and ceased sample distribution. It remains available through authorized distributors like Aetrix Electronics for legacy repair and continuity supply, but no new manufacturing runs are planned.

What is the function of the inverted alarm polarity on DETECT IN in A5350CA-T?

The inverted alarm polarity means A5350CA-T triggers an alarm when the voltage on DETECT IN rises *above* the voltage on SENSITIVITY SET - opposite to most ion detectors. This simplifies interface with chambers where smoke increases chamber current, raising the DETECT IN voltage relative to the reference.

How does A5350CA-T achieve ultra-low standby current?

A5350CA-T achieves 5.0 μA typical standby current by powering down all circuitry except the oscillator for 1.66 seconds, then activating only for a precise 10 ms smoke sampling window. The internal BiCMOS design minimizes leakage, and the TIMING RES/OSC CAP combination ensures stable low-frequency operation without external clock sources.

Can A5350CA-T be used with photoelectric smoke chambers?

No, A5350CA-T is optimized for ionization-type chambers. Its detector input stage, active guard architecture, and sensitivity thresholds are calibrated for the small currents (picoampere range) and impedance characteristics of ion chambers. Photoelectric chambers require different gain, filtering, and signal conditioning not provided by A5350CA-T.

What is the purpose of GUARD1 and GUARD2 pins on A5350CA-T?

GUARD1 and GUARD2 are active guard outputs that track the voltage on DETECT IN within ±100 mV. They surround the detector input trace on the PCB to eliminate surface leakage currents - a critical requirement for reliable ion chamber operation where input currents are as low as ±1.0 pA. Both guards operate continuously, not just during sampling.