Microchip Technology RE46C145S16F

Overview

RE46C145S16F from Microchip Technology is a CMOS photoelectric smoke detector ASIC with integrated gain-selectable photo amplifier, strobed 100 µs IR detection every 10 seconds, UL217/UL268 recognition, temporal horn pattern per NFPA 72, and interconnect capability for up to 40 detectors. It operates from 6–12 V, draws only 4–6 µA quiescent current in standby, and supports push-button chamber test and 10-minute sensitivity timer mode.

For engineers reviewing the RE46C145S16F datasheet, RE46C145S16F pinout, RE46C145S16F application, or RE46C145S16F equivalent, this page delivers verified functional role (photoelectric smoke sensing ASIC), key timing parameters (10 ms oscillator period, 43 s battery/chamber test interval), UL compliance status, interconnect behavior, and real-world design constraints including C1/C2 gain capacitor mapping and TEST pin dual-mode operation.

Technical Context

The RE46C145S16F implements a low-power, strobed analog smoke detection architecture: internal oscillator enables 100 µs IRED pulses every 10 seconds in standby, with detection rate escalating upon smoke sampling. It uses two external capacitors (C1 for high-gain test mode, C2 for normal-gain standby) to set photoamplifier gain via A = 1 + (C/10), where C is in pF.

Its dual-gain comparator compares DETECT output against an internal VDD−3.5 V reference (or external VSEN voltage in Timer mode), latching alarm after three consecutive valid smoke samples. The IO pin serves as bidirectional interconnect with 670 ms digital filtering, NMOS discharge post-alarm, and constant-current drive during local alarm - enabling synchronized multi-unit response without external logic.

Key Specifications

Pinout & Package

RE46C145S16F is supplied in a 16-lead narrow SOIC (3.90 mm body width) package with standard JEDEC MS-012AC footprint and matte tin (Pb-free) termination.

Key Features

Applications

Equivalent & Alternatives

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

Compared with RE46C125S16F, the RE46C145S16F adds VSEN-controlled Timer Mode for UL-compliant hush; compared with ALLEGRO A5366L, it integrates horn drivers and temporal pattern generation, eliminating external timing components and reducing total solution size by ~35%.

Availability

RE46C145S16F is available at Aetrix Electronics and suitable for residential smoke alarms, commercial interconnected detector systems, hardwired AC/DC detectors, temporary sensitivity adjustment systems, and UL217-certified OEM production requiring stable component supply and long-lifecycle support.

Supply support for RE46C145S16F 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 global semiconductor company specializing in microcontrollers, analog devices, and timing solutions, with ISO/TS-16949 certified manufacturing and broad industrial safety certification expertise.

The RE46C145S16F belongs to Microchip's dedicated smoke detector ASIC product line, designed specifically for UL217/UL268-compliant photoelectric sensing with integrated power management, interconnect, and temporal horn generation - targeting life-safety equipment manufacturers.

FAQ

What is the primary function of the RE46C145S16F in a smoke detector system?

The RE46C145S16F serves as the core photoelectric smoke sensing ASIC, integrating strobed IR detection, gain-selectable photoamplifier, low-power timing control, UL217/UL268-compliant alarm decision logic, temporal horn pattern generation, and bidirectional interconnect. It replaces discrete op-amps, comparators, timers, and drivers - enabling compact, certified, and battery-efficient smoke alarm designs.

How does the RE46C145S16F achieve UL217 and UL268 recognition?

The RE46C145S16F is UL Recognized per File S24036 for use in smoke detectors complying with UL217 (residential) and UL268 (commercial) standards. Its recognition covers internal temporal horn pattern generation (NFPA 72), low-battery and chamber self-test routines, interconnect behavior, and smoke detection algorithm - allowing OEMs to leverage this qualification in end-product certification.

What are the critical external components required for basic RE46C145S16F operation?

Essential external components include: C1 and C2 capacitors (for high/normal gain setting), R9 and R12 resistors with C5 capacitor (for oscillator timing), IRED driver transistor (NPN), piezoelectric horn with HB/HS connections, LED with current-limiting resistor, and photodiode in the smoke chamber. No external microcontroller or timing IC is required for core functionality.

Can the RE46C145S16F be used without the interconnect feature?

Yes - the IO pin can be left unconnected or tied to VSS if interconnect is not required. The RE46C145S16F operates fully as a standalone detector: performing smoke detection, low-battery and chamber tests, LED indication, and horn activation. Interconnect is an optional, scalable enhancement - not a prerequisite for basic alarm functionality.

What is the purpose and activation method of the Timer Mode in the RE46C145S16F?

Timer Mode provides a 10-minute sensitivity reduction to suppress nuisance alarms during transient aerosol events. It activates via a high-to-low transition on the TEST pin while RADJ1/RADJ2 resistors are installed. During Timer Mode, the smoke comparator reference switches from internal VDD−3.5 V to the voltage applied to VSEN (Pin 15), enabling field-adjustable threshold control.