Microchip Technology RE46C194S16

Overview

RE46C194S16 from Microchip Technology is a low-power, low-voltage CMOS photoelectric smoke detector ASIC with integrated 6-bit ADC, programmable IRED drive (50–200 mA), interconnect capability for up to 40 units, and 9-minute hush timer. It operates from 3V lithium or two AA batteries, supports NFPA 72 temporal horn pattern, and performs chamber integrity checks every 43 seconds in standby mode.

For engineers reviewing the RE46C194S16 datasheet, RE46C194S16 pinout, RE46C194S16 application, or RE46C194S16 equivalent, this device serves as a complete, single-chip solution for UL-listed residential and commercial photoelectric smoke alarms requiring battery longevity, programmable sensitivity, and multi-unit interconnect synchronization.

Technical Context

The RE46C194S16 integrates a trimmed oscillator (±6% tolerance) that powers detection circuitry every 10 seconds for 3 ms, with IRED pulse duration programmable from 100–400 µs. Its photo amplifier offers three gain modes-Normal (standby/hysteresis), Low (hush), and High (chamber test)-and uses dual-integration subtraction (IRED-on minus IRED-off) to reject ambient light and offset errors before 6-bit ADC conversion.

It implements a closed-loop boost regulator (VBST = 3.6 V to 10.6 V) driving piezoelectric horn via complementary HS/HB outputs, while IO pin enables bidirectional interconnect with charge-dump arbitration and horn synchronization. EEPROM stores four independent alarm limits (normal, hysteresis, hush, chamber test), long-term drift baseline, and feature configuration bits.

Key Specifications

Pinout & Package

RE46C194S16 is housed in a 16-lead SOIC (150 mil) package with θ_JA = 86.1°C/W, optimized for low-power thermal management in sealed smoke alarm enclosures.

Key Features

Applications

Equivalent & Alternatives

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

Compared with RE46C191 and SM5964, the RE46C194S16 delivers unique value through its integrated interconnect arbitration, long-term drift compensation, and programmable multi-mode IRED drive-enabling UL-compliant, field-maintainable, and battery-optimized smoke detection without external timing or control ICs.

Availability

RE46C194S16 is available at Aetrix Electronics and suitable for residential fire safety systems, commercial interconnected alarm networks, and smart building IoT edge nodes requiring stable component supply, long-lifecycle support, and UL certification readiness.

Supply support for RE46C194S16 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 security ICs, with deep expertise in low-power mixed-signal design for safety-critical applications.

The RE46C194S16 belongs to Microchip's RE46C family of dedicated smoke detector ASICs, engineered specifically to replace discrete analog front-ends and reduce time-to-certification for UL 217–compliant photoelectric alarms.

FAQ

What is the minimum battery voltage required for reliable operation of the RE46C194S16?

The RE46C194S16 operates reliably down to 2.0 V, as confirmed by its Absolute Maximum Ratings and DC Electrical Characteristics table. Its low-battery detection circuit compares VBAT against eight programmable thresholds (2.05–2.85 V), with hysteresis of 100 mV. Below 2.0 V, the device may fail to initiate smoke checks or drive the horn; therefore, 2.0 V is the functional lower limit for continuous operation, and the RE46C194S16 enters low-battery alarm mode when falling below the selected threshold.

How does the RE46C194S16 implement long-term drift compensation, and what is its impact on alarm reliability?

The RE46C194S16 implements long-term drift compensation by storing an initial no-smoke baseline during factory calibration (Test Mode T8) and periodically recalculating a new average from 64 integration measurements over 8 hours. The difference between the stored baseline and the running average is scaled and added to the normal, hysteresis, and hush alarm limits-ensuring consistent sensitivity despite optical aging or dust accumulation. This process occurs automatically and does not require firmware updates or external intervention, directly improving long-term alarm reliability in deployed RE46C194S16 units.

Can the RE46C194S16 drive a piezoelectric horn directly, and what are the voltage/current specifications for the HS and HB outputs?

Yes, the RE46C194S16 drives piezoelectric horns directly via complementary HS and HB outputs. HS connects to the ceramic electrode and HB to the metal electrode, enabling phase-driven acoustic output. Each output supports 20 mA continuous current, with VOH ≥ 8.5 V and VOL ≤ 500 mV at IOL = 16 mA and VBST = 9 V. The internal boost regulator supplies VBST up to 10.6 V, ensuring sufficient voltage headroom for loud, compliant audible alarms across battery discharge profiles.

What is the purpose of the FEED pin on the RE46C194S16, and is it required for photoelectric operation?

The FEED pin on the RE46C194S16 is designed for optional feedback electrode connection in ionization-type smoke chambers-not for photoelectric operation. In photoelectric configurations (the primary use case for RE46C194S16), the FEED pin is unused and must be tied to either VBAT or VSS per the datasheet. Leaving FEED floating violates absolute maximum ratings and risks latch-up or erratic behavior; therefore, proper termination is mandatory even though FEED plays no role in the RE46C194S16's photoelectric smoke detection function.

How does the RE46C194S16 handle interconnect arbitration when multiple detectors alarm simultaneously?

The RE46C194S16 handles interconnect arbitration via its IO pin's built-in charge-dump circuitry and contention window timing. When multiple units assert IO low simultaneously, each device monitors the bus during a 310 ms contention window (TIOCW). If IO remains low beyond this window, the device assumes dominance and proceeds with horn activation; otherwise, it defers. This hardware-level arbitration ensures deterministic, glitch-free alarm propagation across up to 40 RE46C194S16 units without external master controller or software coordination.