Operation from Two AA Batteries, Single Lithium Battery

Low Quiescent Current

4 V, 8.5 V, 10 V, 11.5 V, 17 V Boost Converter

3.3 V Regulator

Piezoelectric Horn Driver

Dual Independently Controlled LED Drivers with Programmable Current up to 200 mA

Programmable Gain Integrating Op Amp with Effective Transimpedance > 20 M at 100 μs

Internal Op Amp for use with CO or Toxic Gas Sensor
• Rail-to-Rail Inputs and Output
• Unity Gain Stable
• 10 kHz Gain Bandwidth Product

Buffered Internal CO Reference

Analog Buffer for Sensing Multiple Internal Voltages (ABUF)

Alarm Interconnect

SPI Controlled

The Microchip RE46C420 is a low-power smoke detector Analog Front End (AFE) intended for battery-powered applications. The AFE provides all the needed analog, interface and power regulation functions for a microcontroller-(MCU) based multicriteria smoke detector. It can be powered by two AA batteries or a single lithium battery. The RE46C420 features an integrating photo amplifier to interface with a photoelectric smoke chamber, two independently controlled programmable LED drivers, an analog buffer circuit (ABUF) for monitoring system voltages, four terminal CO or Toxic Gas sensing, and a 3.3V regulator. The RE46C420 is capable of meeting UL-217 9th Ed and UL-268 7^th Ed specifications and can be easily adapted to new editions with its programmable design and rich feature set. For designs that do not require CO monitoring, see the RE46C421, which instead features a dual-input integrating photo amplifier. For designs that require both CO monitoring and dual photo input, see the RE46C422.