RE46C144

CMOS Photoelectric Smoke Detector ASIC with Interconnect

R&E International

and Timer Mode

A Subsidiary of Microchip Technology Inc.

Product Specification

© 2009 Microchip Technology Inc.

DS22180A-page 6

PIN DESCRIPTIONS

PIN#

PIN NAME

DESCRIPTION

1

C1

The capacitor connected to this pin sets the photo amplifier gain (high) for the

push-to-test and chamber sensitivity test. The size of this capacitor will depend

on the chamber background reflections. A=1+(C1/10) where C1 is in pF. The

gain should be <10000.

2

C2

The capacitor connected to this pin sets the photo amplifier gain (normal) during

standby. The value of this capacitor will depend on the smoke sensitivity

required. A=1+(C2/10) where C2 is in pF.

3

DETECT

Positive input to the photo amplifier. This input is normally connected to the

cathode of an external photo diode operated at zero bias.

4

STROBE

Regulated output voltage of VDD-5 which is active during a test for smoke. This

output is the negative side of the photo amplifier circuitry.

5

VDD

Connect to the positive supply voltage

6

IRED

Provides a regulated pulsed output voltage pre-driver for the infrared emitter.

This output usually drives the base of an NPN transistor.

7

IO

This bidirectional pin provides the capability to interconnect many detectors in a

single system. This pin has an internal pull-down device.

8

HB

This pin is connected to the metal electrode of a piezoelectric transducer.

9

HS

HS is a complementary output to HB and connects to the ceramic electrode of

the piezoelectric transducer.

10

FEED

Usually connected to the feedback electrode through a current limiting resistor. If

not used this pin must be connected to VDD or VSS.

11

LED

Open drain NMOS output used to drive a visible LED.

12

COSC

A capacitor connected to this pin with a parallel resistor sets the internal clock

low time which is approximately the clock period.

13

ROSC

A resistor between this pin and pin 12 (COSC) sets the internal clock high time.

This also sets the IRED pulse width (100-200uS).

14

VSS

Connect to the negative supply voltage.

15

VSEN

In the timer mode this input pin can be used to set an external smoke

comparator reference.

16

TEST

This input is used to invoke two test modes and the timer mode. This input has

an internal pull-down.