Allegro MicroSystems A5366CLWTR-T

Overview

A5366CLWTR-T from Allegro MicroSystems is a BiCMOS photoelectric smoke detector IC with integrated photoamplifier, IR LED driver, piezoelectric horn interface, interconnect logic, and UL217/UL268-compliant temporal alarm pattern generation. It operates from 6–12 V, draws only 12 μA average standby current, supports up to 50-unit networking, and delivers calibrated chamber sensitivity monitoring for residential and commercial smoke alarms.

For engineers reviewing the A5366CLWTR-T datasheet, A5366CLWTR-T pinout, A5366CLWTR-T application, or A5366CLWTR-T equivalent, key selection considerations include its 16-pin SOICW package, internal strobe-regulated photoamplifier reference (VDD – 5 V), programmable gain via C1/C2 capacitors, UL-recognized low-battery detection, and three-stage speedup sensing architecture minimizing time-to-alarm while suppressing false triggers.

Technical Context

The A5366CLWTR-T integrates a variable-gain photoamplifier whose gain is set by external capacitors C1 (supervisory mode) and C2 (standby mode), with internal 10% gain boost during local alarm to reduce false triggering. Its internal oscillator drives synchronized STROBE, IRED, and LED timing with nominal periods of 10.4 ms (oscillator), 10 s (standby sampling), and 252 ms (test pulse).

It implements a deterministic interconnect protocol requiring three consecutive high samples on the I/O pin (≈95–137 ms minimum high time) to trigger remote alarm, plus built-in charge-dump circuitry for distributed capacitance immunity. The HUSH pin enables timer mode with reduced sensitivity, and TEST pin initiates push-to-test, diagnostic calibration, or timer reset-all without external microcontroller support.

Key Specifications

Pinout & Package

Package: 16-pin SOICW (suffix LW), Pb-free with 100% matte-tin leadframe plating, JEDEC-standard footprint (MS-013AA), RθJA = 48°C/W on 4-layer PCB.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ISL28134IRZ-T7A and SM555CDR, the A5366CLWTR-T delivers complete, UL-recognized smoke detection functionality in a single IC-including calibrated photoamplifier gain control, deterministic interconnect, temporal horn pattern, and autonomous chamber health monitoring-reducing design cycle time and certification risk.

Availability

A5366CLWTR-T is available at Aetrix Electronics and suitable for residential fire safety systems, commercial building alarm networks, and battery-powered smoke detector manufacturing requiring stable component supply and long-lifecycle support.

Supply support for A5366CLWTR-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 sensor interfaces, with decades of experience in smoke detector ASICs.

The A5366 product line was designed specifically for photoelectric smoke alarms requiring UL217/UL268 recognition, low-power operation, and integrated interconnect-eliminating reliance on discrete op-amps, timers, and microcontrollers.

FAQ

What is the operating voltage range for the A5366CLWTR-T?

The A5366CLWTR-T operates from 6 V to 12 V referenced to VSS. This range supports standard 9 V alkaline batteries and 12 V backup supplies commonly used in residential and commercial smoke alarms. The device includes an internal low-battery detection circuit that triggers a warning chirp when VDD falls below 6.9–7.5 V, ensuring reliable end-of-life indication without external components.

How does the A5366CLWTR-T achieve UL217 and UL268 recognition?

The A5366CLWTR-T is UL Recognized under file #S2113 for use in smoke alarms complying with UL217 (residential) and UL268 (commercial) standards. Recognition covers its integrated temporal horn pattern generation, three-stage speedup sensing algorithm, chamber sensitivity monitoring, and deterministic interconnect logic-all validated per UL test protocols. The IC itself is not a certified alarm but enables full compliance when implemented per Allegro's reference design and layout guidelines.

What is the function of the C1 and C2 pins on the A5366CLWTR-T?

On the A5366CLWTR-T, C1 sets photoamplifier gain during push-to-test and chamber monitor modes (high-gain supervisory), while C2 sets gain during standby (low-gain). Gain is calculated as Ae = 1 + C/10 (C in pF), with C1 typically 0.047 μF and C2 typically 4700 pF. C2 also receives a 10% internal gain boost after local alarm detection to suppress false triggers, and both capacitors require careful layout to avoid noise coupling into the DETECT path.

Can the A5366CLWTR-T drive a piezoelectric horn directly?

Yes, the A5366CLWTR-T directly drives self-resonant piezoelectric horns using its HORN1, HORN2, and FEEDBACK pins. These outputs generate the UL-compliant temporal-3 pattern (0.5 s on / 0.5 s off ×3, then 1.5 s off) without external timing components. The FEEDBACK pin must be connected to the horn's feedback electrode; if unused, it must be tied to VSS. External passive components (e.g., 8.2 kΩ resistor) are required per Allegro's typical application diagram.

How does the interconnect feature work on the A5366CLWTR-T?

The A5366CLWTR-T uses its open-drain I/O pin to interconnect up to 50 units on a shared bus. When any unit detects smoke, it drives I/O high, and all connected units sample this signal every 42 ms. An alarm requires three consecutive high samples plus one additional cycle (≈95–137 ms total high time), providing strong noise immunity. Internal NMOS charge-dump circuitry clears distributed bus capacitance after alarm events, ensuring reliable multi-unit synchronization without external transceivers.