RE46C145_12 Datasheet, PDF(7/26 Page) Microchip Technology – CMOS Photoelectric Smoke Detector ASIC with Interconnect and Timer Mode

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RE46C145_12 Datasheet, PDF (7/26 Pages) Microchip Technology – CMOS Photoelectric Smoke Detector ASIC with Interconnect and Timer Mode

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RE46C145

2.0 PIN DESCRIPTION

The descriptions of the pins are listed in .

TABLE 2-1: PIN FUNCTION TABLE

RE46C145

PDIP, SOIC, SOICN

Symbol

Function

DETECT

STROBE

VDD

IRED

FEED

LED

COSC

ROSC

VSS

VSEN

TEST

High Gain Capacitor Pin

Normal Gain Capacitor Pin

Photo Diode Input

Strobed Detection Negative Supply

Positive Power Supply

Infrared Emitting Diode Pin

Interconnect Pin

Horn Brass, Inverted Output

Horn Silver Output

Horn Feedback Pin

LED Driver Pin

Oscillator Capacitor Input

Oscillator Resistor Drive Low

Negative Power Supply

HushTimer Sensitivity Pin

Test Pin

2.1 High/Normal Gain Capacitor Pins

(C1, C2)

The capacitor connected to C1 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 expressed in pF. The gain should be

<10000.

The capacitor connected to C2 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 expressed in pF.

2.2 Photo Diode Input (DETECT)

This input is normally connected to the cathode of an

external photo diode operated at zero bias.

2.3 Strobed Detection

Negative Supply (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 reference circuitry.

2.4 Positive Power Supply (VDD)

The VDD pin is the deviceâs positive power supply input.

2.5 Infrared Emitting Diode Pin (IRED)

Provides a regulated pulsed output voltage pre-driver

for the infrared emitter. This output usually drives the

base of an NPN transistor.

2.6 Interconnect Pin (IO)

This bidirectional pin provides the capability to

interconnect many detectors in a single system. This

pin has an internal pull-down device.

2.7 Horn Brass, Inverted Output (HB)

HB pin is connected to the metal electrode of a

piezoelectric transducer.

2.8 Horn Silver Output Pin (HS)

HS pin is a complementary output to HB and connects

to the ceramic electrode of the piezoelectric transducer.

ï£ 2009-2012 Microchip Technology Inc.

DS22181C-page 7

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