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RE46C122: 产品描述CMOS Ionization Smoke Detector ASIC with Interconnect and Timer Mode Preliminary Product Specification; 文件大小171KB，共9页; 制造商ETC

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RE46C122概述

CMOS Ionization Smoke Detector ASIC with Interconnect and Timer Mode Preliminary Product Specification

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R&E International

RE46C122

CMOS Ionization Smoke Detector ASIC with Interconnect and Timer Mode

Preliminary Product Specification

General Description

The RE46C122 is low power CMOS ionization type

smoke detector IC. With few external components this

circuit will provide all the required features for an

ionization type smoke detector.

An internal oscillator strobes power to the smoke

detection circuitry for 10.5mS every 1.66 seconds to

keep standby current to a minimum. A check for a low

battery condition is performed every 40 seconds when

in standby. The temporal horn pattern supports the

NFPA 72 emergency evacuation signal.

An interconnect pin allows multiple detectors to be

connected such that when one units alarms all units will

sound.

An internal 10 minute timer allows for a separate button

to be used for reduced sensitivity mode.

Although this device was designed for smoke detection

utilizing an ionization chamber it could be used in a

variety of security applications.

Utilizing low power CMOS technology the RE46C122

was designed for use in smoke detectors that comply

with Underwriters Laboratory Specification UL217 and

UL268.

Features

•

Guard Outputs for Ion Detector Input

+/-0.75pA Detect Input Current

Internal Reverse Battery Protection

Low Quiescent Current Consumption (<6uA)

Available in 16L PDIP or 16L N SOIC

ESD Protection on all Pins

Internal Low Battery Detection

Interconnect up to 40 Detectors

10 Minute Timer for Sensitivity Control

Compatible with Allegro A5367

Pin Configuration

TSTART

LBADJ

TSTROBE

LED

VDD

RBIAS

FEED

GUARD2

DETECT

GUARD1

VSEN

OSCAP

VSS

ABSOLUTE MAXIMUM RATINGS

PARAMETER

Supply Voltage

Input Voltage Range Except FEED

FEED Input Voltage Range

Reverse Battery Time

Input Current except FEED

Operating Temperature

Storage Temperature

Maximum Junction Temperature

SYMBOL

infd

STG

VALUE

-.3 to V

+.3

-10 to +22

-10 to 60

-55 to 125

150

UNITS

°C

Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are

stress ratings only and operation at these conditions for extended periods may affect device reliability.

This product utilizes CMOS technology with static protection; however proper ESD prevention procedures should be used

when handling this product. Damage can occur when exposed to extremely high static electrical charge.

Telephone 610.992.0727

Page 1 of 9

E-mail: rande@randeint.com

DS-RE46C122-060104

This datasheet contains PROPRIETARY and CONFIDENTIAL information.

Facsimile 610.992.0734

RE46C122

CMOS Ionization Smoke Detector ASIC with Interconnect and Timer Mode

Preliminary Product Specification

R&E International

DEVICE DESCRIPTION and APPLICATION NOTES

Internal Timing – With external components as indicated on the application drawing the period of the

oscillator is nominally 1.67 seconds in standby. Every 1.66 seconds the detection circuitry is powered up

for 10.5mS and the status of the smoke comparator is latched. In addition every 40 seconds the LED

driver is turned on for 10.5mS and the status of the low battery comparator is latched. The smoke

comparator status is not checked during the low battery test, during the low battery horn warning chirp, or

when the horn is on due to an alarm condition.

If an alarm condition is detected the oscillator period increases to 41.5mS.

Due to the low currents used in the oscillator the capacitor on pin 12 should be a low leakage type.

Oscillator accuracy will depend mainly on the tolerance of the RBIAS resistor and OSCAP capacitor.

Smoke Detection Circuit – The smoke comparator compares the ionization chamber voltage to a voltage

derived from a resistor divider across VDD. This divider voltage is available externally on pin 13 (VSEN).

When smoke is detected this voltage is internally increased by 130mV nominal to provide hysteresis and

make the detector less sensitive to false triggering.

Pin 13 (VSEN) can be used to modify the internal set point for the smoke comparator by use of external

resistors to VDD or VSS. Nominal values for the internal resistor divider are indicated on the block

diagram. These internal resistor values can vary by up to ±20% but the resistor matching should be <2%

on any one device. Transmission switches on VSEN and LBADJ prevent any interaction from the external

adjustment resistors.

The guard amplifier and outputs are always active and will be within 50mV of the DETECT input to

reduce surface leakage. The guard outputs also allow for measurement of the DETECT input without

loading the ionization chamber.

Low Battery Detection - An internal reference is compared to the voltage divided VDD supply. The battery

can be checked under load via the LED low side driver output since low battery status is latched at the

end of the 10.5mS LED pulse. Pin 3 (LBADJ) can be used to modify the low battery set point by placing a

resistor to VDD or VSS. Transmission switches on VSEN and LBADJ prevent any interaction from

external adjustment resistance.

LED Pulse – The LED is pulsed on for 10.5mS every 40S in standby. In alarm the LED is pulsed on for

10.5mS every 1S.

Interconnect – Pin 2 (IO) provides the capability to common many detectors in a single system. If a single

unit goes into alarm the IO pin is driven high. This high signal causes the interconnected units to alarm.

The LED flashes every 1S for 10.5mS on the signaling unit and is inhibited on the units that are in alarm

due to the IO signal. An internal sink device on the IO pin helps to discharge the interconnect line. This

charge dump device is active for 1 clock cycle after the unit exits the alarm condition (1.67S).

The interconnect input has a 500mS maximum digital filter. This allows for interconnection to other types

of alarms (carbon monoxide for example) that may have a pulsed interconnect signal.

Testing - By holding pin 12 (OSCAP) low the internal power strobe is active. Functional testing can be

accelerated by driving pin 12 with a 4kHZ square wave however the 10.5mS strobe period must be

maintained for proper operation of the analog circuitry. Please refer to the timing diagrams.

Timer Mode – The transition of pin 1 (TSTART) from a high to low level initiates a ten minute timer.

During this 10 minute period the open drain NMOS on pin 4 (TSTROBE) is strobed on with the internal

clock. A resistor connected to this pin could be used to modify the detector sensitivity for the timer period.

Telephone 610.992.0727

Page 5 of 9

E-mail: rande@randeint.com

DS-RE46C122-060104

This datasheet contains PROPRIETARY and CONFIDENTIAL information.

Facsimile 610.992.0734

RE46C122

RE46C122概述

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