R&E International
A Subsidiary of Microchip Technology Inc.
RE46C122
CMOS Ionization Smoke Detector ASIC with Interconnect and Timer Mode
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.
© 2009 Microchip Technology Inc.
DS22173B-page 1
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.
The RE46C122 is recognized by Underwriters
Laboratories for use in smoke detectors that comply
with specification UL217 and UL268.
Features
• >1500V ESD Protection (HBM) on all Pins
• Guard Outputs for Ion Detector Input
• +/-0.75pA Detect Input Current
• Internal Reverse Battery Protection
• Low Quiescent Current Consumption (<6.5uA)
• Available in 16L PDIP or 16L N SOIC
• Internal Low Battery Detection
• Power Up Low Battery Test
• Interconnect up to 40 Detectors
• 10 Minute Timer for Sensitivity Control
• Compatible with Allegro A5367
• UL Recognized per File S24036
• Available in Standard Packaging or RoHS
Compliant Pb Free Packaging.
Pin Configuration
16
1
GUARD2
TSTART
2
DETECT
IO
15
3
GUARD1
LBADJ
14
TSTROBE
4
VSEN
13
ABSOLUTE MAXIMUM RATINGS
PARAMETER SYMBOL
VALUE
UNITS
Supply Voltage
V
DD
15 V
Input Voltage Range Except FEED, IO
V
in
-.3 to V
dd
+.3 V
FEED Input Voltage Range
V
infd
-10 to +22
V
IO Input Voltage Range
V
io1
-.3 to 17
V
Reverse Battery Time
T
RB
5 S
Input Current except FEED
I
in
10
mA
Operating Temperature
T
A
-10 to 60
°C
Storage Temperature
T
STG
-55 to 125
°C
Maximum Junction Temperature
T
J
150
°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.
OSCAP
5
12
LED
VDD
RBIAS
FEED
6
HS
11
7
HB
10
VSS
8
9
RE46C122
CMOS Ionization Smoke Detector ASIC with R&E International
Interconnect and Timer Mode
A Subsidiary of Microchip Technology
Inc.
Product Specification
© 2009 Microchip Technology Inc.
DS22173B-page 2
DC Electrical Characteristics at TA = 25°C, VDD=9V, OSCAP=.1uF, RBIAS=8.2MΩ, VSS=0V (unless
otherwise noted)
Limits
Parameter Symbol
Test
Pin Test
Conditions Min Typ Max Units
Supply Voltage
V
DD
6
Operating
6 12
V
I
DD1
6
RBIAS=8.2MΩ, OSCAP=.1uF
5
6.5
uA
Supply Current
I
DD2
6
RBIAS=8.2MΩ, OSCAP=.1uF;Vdd=12V
9
uA
V
IH1
8
6.2 4.5
V
V
IH2
2
No Local Alarm, IO as an Input
3
V
Input Voltage High
V
IH3
1
4.5 V
V
IL1
8
4.5 2.7 V
V
IL2
2
No Local Alarm, IO as an Input
1
V
Input Voltage Low
V
IL3
1
2.5
V
IL
DET1
15
VDD=9V, DETECT=VSS, 0-40% RH
-0.75
pA
IL
DET2
15
VDD=9V, DETECT=VSS, 85% RH
Note 1
-1.50
pA
Input Leakage Low
IL
FD
8
FEED=-10V
-50
uA
IH
DET1
15
VDD=9V, DETECT=VDD, 0-40% RH
0.75
pA
IH
DET2
15
VDD=9V, DETECT=VDD, 85% RH
Note 1
1.50
pA
IH
FD
8
FEED=22V
50
uA
Input Leakage High
I
IOL2
2
No Alarm, Vio=17V
150
uA
Output Off Leakage High
I
IOHZ
4,5
Outputs Off
1
uA
Input Pull Down Current
I
PD1
1
TSTART=9V
20 50 80 uA
Output High Voltage
V
OH1
10,11
IOH=-16mA, VDD=7.2V
6.3 V
V
OL1
10,11
IOL=16mA, VDD=7.2V
.9
V
V
OL2
4
IOL=500ua
.5
V
Output Low Voltage
V
OL3
5
IOL=10mA, VDD=7.2V
1
V
I
IOL1
2
No Alarm, Vio=Vdd-2V
25 60
uA
I
IOH1
2
Alarm, Vio=Vdd-2V or Vio=0V
-4 -16
mA
Output Current
I
IODMP
2
At Conclusion of Local Alarm or Test,
Vio=1V
5 mA
Low Battery Voltage
V
LB
6
T
A
=-10 to 60ºC, Note 3
7.2 7.5 7.8 V
V
SET1
13
48.5 50 51.5
%V
DD
Internal Sensitivity Set Voltage
V
SET2
3
65.5 %V
DD
RE46C122
CMOS Ionization Smoke Detector ASIC with R&E International
Interconnect and Timer Mode
A Subsidiary of Microchip Technology
Inc.
Product Specification
© 2009 Microchip Technology Inc.
DS22173B-page 3
DC Electrical Characteristics – Continued
Limits
Parameter Symbol
Test
Pin Test
Conditions Min Typ Max Units
VG
OS1
14,15
Guard Amplifier
-50 50
mV
VG
OS2
15,16
Guard Amplifier
-50 50
mV
Offset Voltage
VG
OS3
13,15
Smoke Comparator
-50 50
mV
V
CM1
14,15
Guard Amplifier, Note 2
2
V
DD
-.5
V
Common Mode Voltage
V
CM2
13,15
Smoke Comparator, Note 2
.5
V
DD
-2
V
Output Impedance
Z
OUT
14,16
Guard Amplifier Outputs, Note 2
10 k
Ω
Hysteresis
V
HYS
13
No Alarm to Alarm Condition
90 130 170 mV
Note 1: Sample test only.
Note 2: Not 100% production tested.
Note 3: Production test at room with temperature guardbanded limits.
AC Electrical Characteristics at TA = 25°C, VDD=9V, OSCAP=.1uF, RBIAS=8.2MΩ, VSS=0V (unless
otherwise noted)
Limits
Parameter Symbol
Test
Pin Test
Conditions Min Typ Max Units
T
PER1
12
No Alarm Condition
1.34 1.67 2
S
Oscillator Period
T
PER2
12
Alarm Condition
37.5 41.5 45.8 mS
Oscillator Pulse Width
T
PW
5
Operating
9.4 10.5 12.9 mS
LED On Time
T
LON
5
Operating
9.4 10.5 12.9 mS
T
LOF1
5
Standby, No Alarm
32 40 48 S
T
LOF2
5
Alarm Condition
.8 1 1.2 S
LED Off Time
T
LOF3
5
Timer Mode, No Alarm
8 10 12 S
T
HON1
10,11
Operating, Alarm Condition, Note 4
450 500 550 mS
Horn On Time
T
HON2
10,11
Low Battery, No Alarm
9.4 10.5 12.9 mS
T
HOF1
10,11
Operating, Alarm Condition, Note 4
450 500 550 mS
T
HOF2
10,11
Operating, Alarm Condition, Note 4
1.35 1.5 1.65 S
Horn Off Time
T
HOF3
10,11
Low Battery, No Alarm
32 40 48 S
IO Charge Dump Duration
T
IODMP
2
At Conclusion of Local Alarm or Test
1.34 1.67 2.0 S
IO Delay
T
IODLY1
2
From Start of Local Alarm to IO Active
3 S
IO Filter
T
IOFILT
2
IO pulse width guaranteed to be filtered.
IO as Input, No Local Alarm
450
mS
Remote Alarm Delay
T
IODLY2
2
No Local Alarm, IO as input, From IO
active to Horn Active
.450 2.2 S
Timer Period
T
TPER
4
No Alarm
8 10 12 Min
Note 4 – See timing diagram for horn temporal pattern.
All timing except for T
PER
and T
PW
are guaranteed by functional tests.
RE46C122
CMOS Ionization Smoke Detector ASIC with R&E International
Interconnect and Timer Mode
A Subsidiary of Microchip Technology
Inc.
Product Specification
Functional Block Diagram
© 2009 Microchip Technology Inc.
DS22173B-page 4
RE46C122
CMOS Ionization Smoke Detector ASIC with R&E International
Interconnect and Timer Mode
A Subsidiary of Microchip Technology
Inc.
Product Specification
© 2009 Microchip Technology Inc.
DS22173B-page 5
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 nominal digital filter. This allows for interconnection to other types of alarms
(carbon monoxide for example) that may have a pulsed interconnect signal.
Testing – At power up all internal registers are reset. The low battery set point can be tested at power up by
holding FEED and OSCAP low at power up. HB will change state as VDD passes through the low battery set
point. By holding pin 12 (OSCAP) low the internal power strobe is active. Functional testing can be accelerated by
driving pin 12 with a 4 kHz 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.
RE46C122
CMOS Ionization Smoke Detector ASIC with R&E International
Interconnect and Timer Mode
A Subsidiary of Microchip Technology
Inc.
Product Specification
Typical Application
Figure 2
Notes:
Select R9 to reduce sensitivity during the timer mode.
R3, R4 and C1 are typical values and may be adjusted to maximize sound pressure.
C2 should be located as close as possible to the device power pins.
Route the pin 8 PC board trace away from pin 7 to avoid coupling.
© 2009 Microchip Technology Inc.
DS22173B-page 6
RE46C122
CMOS Ionization Smoke Detector ASIC with R&E International
Interconnect and Timer Mode
A Subsidiary of Microchip Technology
Inc.
Product Specification
Typical Single Button Application
Figure 3
Notes:
Select R5 and R6 for the correct level to test the ion chamber. The voltage level on pin 1 (TSTART) must be
greater than the VIH level to initiate the timer. Pin 1 has an internal 180K nominal pull down which must be
considered.
Select R9 to reduce sensitivity during the timer mode.
R3, R4 and C1 are typical values and may be adjusted to maximize sound pressure.
C2 should be located as close as possible to the
device power pins.
Route the pin 8 PC board trace away from pin 7 to
avoid coupling.
© 2009 Microchip Technology Inc.
DS22173B-page 7
RE46C122
CMOS Ionization Smoke Detector ASIC with R&E International
Interconnect and Timer Mode
A Subsidiary of Microchip Technology
Inc.
Product Specification
Timing Diagram (non Timer Mode)
Standby Mode; No Low Battery; No Alarm
Alarm; No Low Battery
Alarm; Low Battery
Oscillator
1.67S
10.5mS
Internal Clock
24 Clock Cycles (40 S)
LED
Sample Smoke
Low Battery Warning Chirp
Horn
See Figure Below for Complete Horn Cycle
T
IODLY1
IO (Pin 2) as Output
Timing not same scale as above
IO Charge Dump
T
IOFILT
IO ( Pin 2) as Input
LED supressed in remote alarm mode
T
IODLY2
Horn
Start of horn temporal pattern is not synchronized to an external alarm
Horn pattern not self completing for external alarm,see timing below for complete horn cycle
Internal Clock
Notes:
1. Smoke is not sampled when the horn is active. Horn cycle is self completing in local alarm.
2. Low battery warning chirp is suppressed in local or remote alarm
3. IO Dump active only in local alarm, inactive if external alarm
T
HON1
T
HOF1
Complete Temporal Horn Pattern
Pin 15 > Pin 13
Pin 15 > Pin 13
Pin 13 > Pin 15; 130mV Level Shift on Pin 13
No Alarm; Low Battery
T
HOF2
24 Clock Cycles (1S)
© 2009 Microchip Technology Inc.
DS22173B-page 8
RE46C122
CMOS Ionization Smoke Detector ASIC with R&E International
Interconnect and Timer Mode
A Subsidiary of Microchip Technology
Inc.
Product Specification
Timing Diagram (Timer Mode)
Oscillator
10.5mS
1.67S
Internal Clock
TSTART
T
LOF3
LED
Outputs High Z
TSTROBE
T
TPER
© 2009 Microchip Technology Inc.
DS22173B-page 9
RE46C122
CMOS Ionization Smoke Detector ASIC with R&E International
Interconnect and Timer Mode
A Subsidiary of Microchip Technology
Inc.
Product Specification
Information contained in this publication regarding device
applications and the like is provided only for your convenience and
may be superseded by updates. It is your responsibility to ensure
that your application meets with your specifications. MICROCHIP
MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY
KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL,
STATUTORY OR OTHERWISE, RELATED TO THE
INFORMATION, INCLUDING BUT NOT LIMITED TO ITS
CONDITION, QUALITY, PERFORMANCE, MERCHANTABILITY
OR FITNESS FOR PURPOSE. Microchip disclaims all liability
arising from this information and its use. Use of Microchip devices in
life support and/or safety applications is entirely at the buyer’s risk,
and the buyer agrees to defend, indemnify and hold harmless
Microchip from any and all damages, claims, suits, or expenses
resulting from such use. No licenses are conveyed, implicitly or
otherwise, under any Microchip intellectual property rights.
Trademarks
The Microchip name and logo, the Microchip logo, Accuron,
dsPIC, K
EE
L
OQ
, K
EE
L
OQ
logo,
MPLAB, PIC, PICmicro,
PICSTART, rfPIC, SmartShunt and UNI/O are registered
trademarks of Microchip Technology Incorporated in the U.S.A.
and other countries.
FilterLab, Hampshire, Linear Active Thermistor, MXDEV, MXLAB,
SEEVAL, SmartSensor and The Embedded Control Solutions
Company are registered trademarks of Microchip Technology
Incorporated in the U.S.A.
Analog-for-the-Digital Age, Application Maestro, CodeGuard,
dsPICDEM, dsPICDEM.net, dsPICworks, dsSPEAK, ECAN,
ECONOMONITOR, FanSense, In-Circuit Serial Programming,
ICSP, ICEPIC, Mindi, MiWi, MPASM, MPLAB Certified logo,
MPLIB, MPLINK, mTouch, nanoWatt XLP, PICkit, PICDEM,
PICDEM.net, PICtail, PIC
32
logo, PowerCal, PowerInfo,
PowerMate, PowerTool, REAL ICE, rfLAB, Select Mode, Total
Endurance, TSHARC, WiperLock and ZENA are trademarks of
Microchip Technology Incorporated in the U.S.A. and other
countries.
SQTP is a service mark of Microchip Technology Incorporated in
the U.S.A.
All other trademarks mentioned herein are property of their
respective companies.
© 2009, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.
Printed on recycled paper.
Microchip received ISO/TS-16949:2002 certification for its worldwide
headquarters, design and wafer fabrication facilities in Chandler and
Tempe, Arizona; Gresham, Oregon and design centers in California and
India. The Company’s quality system processes and procedures are for its
PIC
®
MCUs and dsPIC
®
DSCs, K
EE
L
OQ
®
code hopping devices, Serial
EEPROMs, microperipherals, nonvolatile memory and analog products. In
addition, Microchip’s quality system for the design and manufacture of
development systems is ISO 9001:2000 certified.
© 2009 Microchip Technology Inc.
DS22173B-page 10