Microchip Technology RE46C145SW16F

Overview

RE46C145SW16F from Microchip Technology is a CMOS photoelectric smoke detector ASIC with integrated gain-selectable photo amplifier, strobed 100 µs IR detection every 10 seconds (4 µA standby current), UL217/UL268 recognition, temporal horn pattern per NFPA 72, and interconnect capability for up to 40 detectors in residential fire alarm systems.

For engineers reviewing the RE46C145SW16F datasheet, RE46C145SW16F pinout, RE46C145SW16F application, or RE46C145SW16F equivalent, this page delivers verified functional architecture, real-world timing behavior (e.g., 10.5 ms oscillator period, 43 s battery/chamber test interval), UL-compliant alarm sequencing, and precise SOIC-16W package mapping - all confirmed from Microchip DS22181C.

Technical Context

The RE46C145SW16F implements a dual-gain photo amplifier (C1/C2 capacitor-selectable), internal VDD–3.5V reference comparator, and strobe-controlled 100 µs IRED pulsing synchronized to a 10 ms oscillator period set by R9/R12/C5. It executes three consecutive smoke detections before triggering local alarm with horn temporal pattern (500 ms on / 500 ms off).

Its bidirectional IO pin supports interconnect via constant-current drive (local alarm) and 670 ms digital filtering (remote alarm input), while diagnostic mode repurposes VSEN as photoamp output and IO as gain selector - all operating within –25°C to +75°C with 15 V absolute max rating.

Key Specifications

Pinout & Package

RE46C145SW16F is supplied in a 16-lead wide SOIC package (7.50 mm body width, JEDEC MS-013AC), with thermal resistance θ_JA = 80°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with RE46C144SW16F, RE46C145SW16F adds VSEN-based timer mode for temporary sensitivity reduction; versus ALLEGRO A5366L, it provides factory UL recognition and integrated interconnect logic - reducing certification risk and component count.

Availability

RE46C145SW16F is available at Aetrix Electronics and suitable for residential smoke alarms, commercial fire panels, temporary construction safety systems, and hotel/motel life safety deployments requiring stable component supply, long-lifecycle support, and UL-compliant design assurance.

Supply support for RE46C145SW16F 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

Microchip Technology is a U.S.-based semiconductor company specializing in microcontrollers, analog devices, and security ICs, with ISO/TS 16949-certified manufacturing and global technical support infrastructure.

The RE46C145SW16F belongs to Microchip's dedicated smoke detector ASIC product line, engineered specifically for UL217/UL268-compliant photoelectric fire detection systems with minimal external components and robust self-test capabilities.

FAQ

What is the function of the VSEN pin on the RE46C145SW16F?

The VSEN pin on the RE46C145SW16F serves as the hush/timer sensitivity input. During the 10-minute timer mode, it replaces the internal VDD–3.5 V smoke comparator reference with an externally applied voltage, enabling field-adjustable sensitivity reduction. If left unconnected or tied to VSS, timer mode is disabled. This pin is not used in normal standby or alarm operation.

How does the RE46C145SW16F achieve its 4 µA standby current?

The RE46C145SW16F achieves 4 µA standby current by powering down analog circuitry between 10-second intervals, activating detection only for 100 µs per cycle using the STROBE (VDD–5 V) and IRED outputs. The internal oscillator runs at 10.5 ms, and smoke sampling occurs once every 10 seconds - minimizing average current while maintaining responsiveness. This behavior is confirmed in DS22181C, page 3, IDD1 specification.

Is the RE46C145SW16F pin-compatible with the Allegro A5366?

Yes, the RE46C145SW16F is explicitly stated in its datasheet (DS22181C, page 1) as "Compatible with Allegro A5366". Pin functions, timing behavior, and interconnect logic match closely, though RE46C145SW16F adds UL recognition, timer mode, and enhanced self-test features not present in the A5366. No PCB layout changes are required for direct substitution.

What happens during the chamber test performed every 43 seconds on the RE46C145SW16F?

Every 43 seconds, the RE46C145SW16F performs a chamber integrity test by switching to high-gain mode (using C1 capacitor) and measuring background reflections in the smoke chamber. Two consecutive failures trigger a 10 ms horn chirp every 43 seconds - distinct from low-battery chirps and suppressed during local/remote alarms. This test validates optical path cleanliness without user intervention.

Does the RE46C145SW16F support both PDIP and SOIC packages, and what does 'SW' signify?

Yes, the RE46C145SW16F uses the 'SW' suffix per Microchip's Product Identification System (DS22181C, page 23), denoting the Small Plastic Outline – Wide (7.50 mm body) 16-lead SOIC package. Other variants include 'E' for PDIP and 'S' for narrow SOIC. All share identical electrical functionality and pinout; only thermal resistance (θ_JA = 80°C/W for SW) and mechanical dimensions differ.