R&E International
A Subsidiary of Microchip Technology Inc.
RE46C128
CMOS Ionization Smoke Detector ASIC with Interconnect
Product Specification
General Description
The RE46C128 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.
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 RE46C128
was designed for use in smoke detectors that comply
with Underwriters Laboratory 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
Compatible with Allegro A5364
Available in Standard Packaging or RoHS Compliant
Pb Free Packaging.
Pin Configuration
N/C
IO
LBADJ
N/C
LED
VDD
RBIAS
FEED
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
GUARD2
DETECT
GUARD1
VSEN
OSCAP
HS
HB
VSS
ABSOLUTE MAXIMUM RATINGS
PARAMETER
Supply Voltage
Input Voltage Range Except FEED, IO
FEED Input Voltage Range
IO Input Voltage Range
Reverse Battery Time
Input Current except FEED
Operating Temperature
Storage Temperature
Maximum Junction Temperature
SYMBOL
V
DD
V
in
V
infd
V
io1
T
RB
I
in
T
A
T
STG
T
J
VALUE
15
-.3 to V
dd
+.3
-10 to +22
-.3 to 17
5
10
-10 to 60
-55 to 125
150
UNITS
V
V
V
V
S
mA
°C
°C
°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.
© 2009 Microchip Technology Inc.
DS22171A-page 1
RE46C128
CMOS Ionization Smoke Detector ASIC with Interconnect
Product Specification
R&E International
A Subsidiary of Microchip Technology Inc.
DC Electrical Characteristics at TA = 25°C, VDD=9V, OSCAP=.1uF, RBIAS=8.2MΩ, VSS=0V (unless
otherwise noted)
Test
Pin
6
6
6
8
2
8
2
15
15
8
15
15
8
2
5
10,11
10,11
5
2
2
2
6
13
3
No Local Alarm, IO as an Input
VDD=9V, DETECT=VSS, 0-40% RH
VDD=9V, DETECT=VSS, 85% RH
Note 1
FEED=-10V
VDD=9V, DETECT=VDD, 0-40% RH
VDD=9V, DETECT=VDD, 85% RH
Note 1
FEED=22V
No Alarm, Vio=17V
Outputs Off
IOH=-16mA, VDD=7.2V
IOL=16mA, VDD=7.2V
IOL=10mA, VDD=7.2V
No Alarm, Vio=Vdd-2V
Alarm, Vio=Vdd-2V or Vio=0V
At Conclusion of Local Alarm or Test,
Vio=1V
T
A
=-10 to 60ºC, Note 3
Parameter
Supply Voltage
Supply Current
Symbol
V
DD
I
DD1
I
DD2
V
IH1
V
IH2
V
IL1
V
IL2
IL
DET1
IL
DET2
IL
FD
Test Conditions
Operating
RBIAS=8.2MΩ, OSCAP=.1uF
RBIAS=8.2MΩ, OSCAP=.1uF;Vdd=12V
Min
6
Limits
Typ
Max
12
5
6.5
9
Units
V
uA
uA
V
V
Input Voltage High
6.2
No Local Alarm, IO as an Input
3
4.5
4.5
2.7
1
-0.75
-1.50
-50
0.75
1.50
50
150
1
Input Voltage Low
V
V
pA
pA
uA
pA
pA
uA
uA
uA
V
V
V
uA
mA
mA
Input Leakage Low
Input Leakage High
IH
DET1
IH
DET2
IH
FD
I
IOL2
Output Off Leakage High
Output High Voltage
Output Low Voltage
I
IOHZ
V
OH1
V
OL1
V
OL3
I
IOL1
I
IOH1
I
IODMP
6.3
.9
1
25
-4
5
7.2
48.5
7.5
50
65.5
7.8
51.5
60
-16
Output Current
Low Battery Voltage
Internal Sensitivity Set Voltage
V
LB
V
SET1
V
SET2
V
%V
DD
%V
DD
© 2009 Microchip Technology Inc.
DS22171A-page 2
RE46C128
CMOS Ionization Smoke Detector ASIC with Interconnect
Product Specification
R&E International
A Subsidiary of Microchip Technology Inc.
DC Electrical Characteristics – Continued
Parameter
Offset Voltage
Symbol
VG
OS1
VG
OS2
VG
OS3
Test
Pin
14,15
15,16
13,15
14,15
13,15
14,16
13
Test Conditions
Guard Amplifier
Guard Amplifier
Smoke Comparator
Guard Amplifier, Note 2
Smoke Comparator, Note 2
Guard Amplifier Outputs, Note 2
No Alarm to Alarm Condition
Min
-50
-50
-50
2
.5
Limits
Typ
Max
50
50
50
V
DD
-.5
V
DD
-2
Units
mV
mV
mV
V
V
kΩ
mV
Common Mode Voltage
V
CM1
V
CM2
Z
OUT
V
HYS
Output Impedance
Hysteresis
10
90
130
170
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)
Test
Pin
12
12
5
5
5
5
5
10,11
10,11
10,11
10,11
10,11
2
2
2
2
Parameter
Oscillator Period
Symbol
T
PER1
T
PER2
T
PW
T
LON
T
LOF1
T
LOF2
T
LOF3
Test Conditions
No Alarm Condition
Alarm Condition
Operating
Operating
Standby, No Alarm
Alarm Condition
Timer Mode, No Alarm
Operating, Alarm Condition, Note 4
Low Battery, No Alarm
Operating, Alarm Condition, Note 4
Operating, Alarm Condition, Note 4
Low Battery, No Alarm
At Conclusion of Local Alarm or Test
From Start of Local Alarm to IO Active
IO pulse width guaranteed to be filtered.
IO as Input, No Local Alarm
No Local Alarm, IO as input, From IO
active to Horn Active
Min
1.34
37.5
9.4
9.4
32
.8
8
450
9.4
450
1.35
32
1.34
Limits
Typ
Max
1.67
41.5
10.5
10.5
40
1
10
500
10.5
500
1.5
40
1.67
3
450
2
45.8
12.9
12.9
48
1.2
12
550
12.9
550
1.65
48
2.0
Units
S
mS
mS
mS
S
S
S
mS
mS
mS
S
S
S
S
mS
S
Oscillator Pulse Width
LED On Time
LED Off Time
Horn On Time
T
HON1
T
HON2
T
HOF1
T
HOF2
T
HOF3
Horn Off Time
IO Charge Dump Duration
IO Delay
IO Filter
Remote Alarm Delay
T
IODMP
T
IODLY1
T
IOFILT
T
IODLY2
.450
2.2
Note 4 – See timing diagram for horn temporal pattern.
All timing except for T
PER
and T
PW
are guaranteed by functional tests.
© 2009 Microchip Technology Inc.
DS22171A-page 3
RE46C128
CMOS Ionization Smoke Detector ASIC with Interconnect
Product Specification
R&E International
A Subsidiary of Microchip Technology Inc.
RE46c128 Functional Block Diagram
Figure 1
© 2009 Microchip Technology Inc.
DS22171A-page 4
RE46C128
CMOS Ionization Smoke Detector ASIC with Interconnect
Product Specification
R&E International
A Subsidiary of Microchip Technology Inc.
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 1000mS 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.
© 2009 Microchip Technology Inc.
DS22171A-page 5
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