R&E International
A Subsidiary of Microchip Technology Inc.
RE46C129
CMOS Ionization Smoke Detector ASIC with Interconnect
Product Specification
© 2009 Microchip Technology Inc. DS22172B-page 1
General Description
The RE46C129 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.
An interconnect pin allows multiple detectors to be
connected such that when one units alarms all units will
sound.
Although this device was designed for smoke detection
utilizing an ionization chamber it could be used in a
variety of security applications.
The RE46C129 is recognized by Underwriters
Laboratories for use in smoke detectors that comply
with specification UL217 and UL268.
Features
• 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
• ESD Protection on all Pins
• Internal Low Battery Detection
• Interconnect up to 40 Detectors
• Compatible with Allegro A5350
• UL Recognized per File S24036
• Available in Standard Packaging or RoHS
Compliant Pb Free Packaging.
Pin Configuration
16
1
GUARD2
NC
2
DETECT
IO
15
3
GUARD1
LBADJ
14
NC
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
RE46C129
CMOS Ionization Smoke Detector ASIC with Interconnect R&E International
Product Specification
A Subsidiary of Microchip Technology
Inc.
© 2009 Microchip Technology Inc. DS22172B-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
4
6.5
uA
Supply Current
I
DD2
6
RBIAS=8.2MΩ, OSCAP=.1uF;Vdd=12V
9
uA
V
IH1
8 FEED
Input
6.3
V
Input Voltage High
V
IH2
2
No Local Alarm, IO as an Input
3
V
V
IL1
8 FEED
Input
2.7 V
Input Voltage Low
V
IL2
2
No Local Alarm, IO as an Input
1
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
5
Outputs Off
1
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
Output Low Voltage
V
OL3
5
IOL=10mA, VDD=7.2V
1
V
I
IOL1
2
No Alarm, Vio=Vdd-2V
25 100
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
Internal Sensitivity Set Voltage
V
SET2
3
65.5 %V
DD
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 kΩ
Note 1: Sample test only
Note 2: Not 100% production tested
Note 3: Production test at room with temperature guardbanded limits.
RE46C129
CMOS Ionization Smoke Detector ASIC with Interconnect R&E International
Product Specification
A Subsidiary of Microchip Technology
Inc.
© 2009 Microchip Technology Inc. DS22172B-page 3
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
LED Off Time
T
LOF2
5
Alarm Condition
.8 1 1.2 S
T
HON1
10,11
Operating, Alarm Condition
141 166 190 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
71 83 95 mS
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
RE46C129
CMOS Ionization Smoke Detector ASIC with Interconnect R&E International
Product Specification
A Subsidiary of Microchip Technology
Inc.
© 2009 Microchip Technology Inc. DS22172B-page 4
Functional Block Diagram
RE46C129
CMOS Ionization Smoke Detector ASIC with Interconnect R&E International
Product Specification
A Subsidiary of Microchip Technology
Inc.
© 2009 Microchip Technology Inc. DS22172B-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. In any alarm condition the horn is on
for 166mS and off for 83mS (typical).
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 must be provided externally on pin 13 (VSEN). See the
application drawing (FIG 2).
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.
The transmission switch on LBADJ is turned on during the LED pulse so an external resistance can be added on
pin 3 to modify the set point if desired.
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 active
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 a local alarm condition (1.67S).
The interconnect input has a 500mS nominal digital filter which will filter out pulsed signals on the IO pin. This
allows for interconnection to other types of alarms (carbon monoxide for example) that may have a pulsed
interconnect signal. This filter will eliminate unwanted random horn activations caused by a pulsed (<500ms
nominal) IO input 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 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. All internal timing is reset after a
power up. By holding pins 8 and 12 low, reducing VDD and monitoring Pin 10 the low battery trip level can be
measured at power up.
RE46C129
CMOS Ionization Smoke Detector ASIC with Interconnect R&E International
Product Specification
A Subsidiary of Microchip Technology
Inc.
© 2009 Microchip Technology Inc. DS22172B-page 6
Typical Application
Figure 2
Notes:
1) C2 should be located as close as possible to the device power pins.
2)
Select R8 and R9 to set the smoke chamber sensitivity.
3)
Low battery trip can be modified by external resistance on pin 3, see device description.
RE46C129
CMOS Ionization Smoke Detector ASIC with Interconnect R&E International
Product Specification
A Subsidiary of Microchip Technology
Inc.
© 2009 Microchip Technology Inc. DS22172B-page 7
Timing Diagram
T
PER1
T
PW
Internal Clock
24 Clock Cycles (40 S)
Ouput High Z
LED
Sample Smoke
T
HON1
T
HOF1
Low Battery Warning Chirp
Horn
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 pattern is not synchronized to an external alarm
Horn pattern not self completing for external alarm
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.
24 Clock Cycles (1S)
Pin 15 < Pin 13
Pin 15 < Pin 13
Pin 15 > Pin 13
RE46C129
CMOS Ionization Smoke Detector ASIC with Interconnect R&E International
Product Specification
A Subsidiary of Microchip Technology
Inc.
© 2009 Microchip Technology Inc. DS22172B-page 8
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