Allegro MicroSystems A5358CA

Overview

A5358CA from Allegro MicroSystems is a BiCMOS photoelectric smoke detector IC with integrated interconnect, timer, and piezoelectric horn driver. It provides low-standby current (12 μA), 6–12 V operation, and EN 14604/BS 5446 compliance for residential and commercial fire safety systems.

For engineers reviewing the A5358CA datasheet, A5358CA pinout, A5358CA application, or A5358CA equivalent, key selection considerations include its 16-pin DIP package, dual-gain photoamplifier architecture, interconnect capability for up to 50 units, built-in low-battery detection, and three-stage speedup sensing for rapid alarm response with false-trigger suppression.

Technical Context

The A5358CA integrates a variable-gain photoamplifier with gain selection via external capacitors C1 (supervisory mode) and C2 (standby mode), where Ae = 1 + (C/10) with C in pF. Its internal oscillator sets timing for IRED pulsing (10.4 ms period), STROBE generation (9.5–11.5 ms width), and chamber monitoring cycles.

It implements a noise-immune interconnect protocol requiring three consecutive high samples on the I/O pin (nominally 95–137 ms) to trigger remote alarms, while suppressing LED during remote events and prioritizing local smoke detection. The HUSH pin enables a 10-minute reduced-sensitivity timer mode using an external resistive divider between VDD and STROBE.

Key Specifications

Pinout & Package

Package: 16-pin plastic dual in-line package (DIP), through-hole mounting, Pb-free option available (suffix –T). Thermal resistance R_θJA = 38 °C/W on 4-layer JEDEC PCB.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ISL28022IRZ-T7A and SM5501-16, the A5358CA delivers complete system-level integration - combining photoamplifier control, interconnect logic, piezo drive, and battery management in one die - eliminating at least six external components and simplifying certification to EN 14604.

Availability

A5358CA is available at Aetrix Electronics and suitable for residential fire alarm systems, commercial building interconnect networks, and kitchen nuisance-alarm suppression modules requiring stable component supply and long-life battery operation.

Supply support for A5358CA 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 designer and manufacturer of high-performance magnetic sensors, power ICs, and precision analog devices for automotive, industrial, and consumer markets.

The A5358CA belongs to Allegro's dedicated smoke detector IC product line, engineered specifically to meet European and British fire safety standards (EN 14604, BS 5446) with integrated analog front-end, timing, and alarm signaling functions.

FAQ

What is the operating voltage range for the A5358CA?

The A5358CA operates from 6 V to 12 V referenced to VSS. This range accommodates standard 9 V alkaline batteries and regulated DC supplies. Operation below 6 V may disable internal functions including low-battery detection, while exceeding 12 V risks damage - absolute maximum rating is 15 V. The A5358CA's low-battery threshold is set between 6.9 V and 7.5 V to ensure reliable operation prior to cutoff.

How does the A5358CA achieve low standby current?

The A5358CA achieves 12 μA average standby current by activating its photoamplifier and IRED only for 100 μs every 10 seconds, controlled by an internal oscillator and three-stage speedup sensing circuitry. During inactive periods, most internal blocks - including the horn driver, LED driver, and interconnect logic - remain powered down. This duty-cycled architecture is intrinsic to the A5358CA design and requires no external sleep-mode control signals.

Can the A5358CA drive a piezoelectric horn directly?

Yes, the A5358CA drives self-resonant piezoelectric horns directly using its HORN1, HORN2, and FEEDBACK pins. These outputs form a closed-loop oscillator that sustains mechanical resonance without external transistors or driver ICs. The A5358CA specifies horn on-time (252 ms) and off-time (84 ms) for alarm tones, and horn warning pulse width (9.5–11.5 ms) for low-battery or chamber alerts - all generated internally.

What is the purpose of the C1 and C2 pins on the A5358CA?

The C1 and C2 pins on the A5358CA set photoamplifier gain for different operational modes: C1 configures high gain (Ae = 1 + C1/10, C1 in pF) during push-to-test and chamber monitoring, while C2 sets low gain during standby. The A5358CA automatically selects between them based on mode - e.g., C1 gain activates during TEST button press, and C2 gain increases ~10% after local alarm detection. Both require external capacitors and series resistors per datasheet guidelines.

Does the A5358CA support interconnection with other smoke detectors?

Yes, the A5358CA supports wired interconnection of up to 50 units via its open-collector I/O pin. When any unit detects smoke, it drives its I/O pin high, and all connected units respond with audible alarms. The A5358CA implements noise filtering by requiring three consecutive high samples (nominally 95–137 ms total) before triggering a remote alarm - a feature built into the A5358CA's silicon logic to prevent false triggering from EMI or contact bounce.