5347
SMOKE DETECTOR
WITH INTERCONNECT AND TIMER
TIMER START
I/O
LOW-V SET
TIMER OUT
LED
+ SUPPLY
TIMING RES.
FEEDBACK
1
2
3
4
5
6
7
8
V
SS
V
DD
LOGIC
16
15
14
13
12
11
10
9
GUARD 2
DETECT. IN
GUARD 1
SENSITIVITY
SET
OSC. CAP.
HORN 2
HORN 1
– SUPPLY
Data Sheet
26110.2
The A5347CA is a low-current, CMOS circuit providing all of the
required features for an ionization-type smoke detector. A networking
capability allows as many as 125 units to be interconnected so that if
any unit senses smoke, all units will sound an alarm. In addition,
special features are incorporated to facilitate alignment and test of the
finished smoke detector. This device is designed to comply with
Underwriters Laboratories Specification UL217.
The internal oscillator and timing circuitry keeps standby power to
a minimum by powering down the device for 1.66 seconds and sensing
smoke for only 10 ms. Every 24 on/off cycles, a check is made for low
battery condition. By substituting other types of sensors, or a switch
for the ionization detector, this very-low power device can be used in
numerous other battery-operated safety/security applications.
The A5347CA is supplied in a low-cost, 16-pin dual in-line plastic
package. It is rated for continuous operation over the temperature
range of 0°C to +50°C.
OSC. &
TIMING
HORN
DRIVER
Dwg. PC-004
FEATURES
ABSOLUTE MAXIMUM RATINGS
(Voltages are referenced to V
SS
)
Supply Voltage Range,
V
DD
................................
-0.5 V to +15 V
Input Voltage Range,
V
IN
........................
-0.3 V to V
DD
+ 0.3 V
Input Current, I
IN
...............................
10 mA
Operating Temperature Range,
T
A
.....................................
0
°
C to +50
°
C
Storage Temperature Range,
T
S
...............................
-55
°
C to +125
°
C
CAUTION: CMOS devices have input static
protection but are susceptible to damage when
exposed to extremely high static electrical
charges.
s
s
s
s
s
s
s
Interconnect Up to 125 Detectors
Piezoelectric Horn Driver
Guard Outputs for Detector Input
Pulse Testing for Low Battery
Power-ON Reset
Internal Timer & Control for Reduced Sensitivity
Built-In Hysteresis Reduces False Triggering
Always order by complete part number:
A5347CA
.
5347
SMOKE DETECTOR
with INTERCONNECT
and TIMER
FUNCTIONAL BLOCK DIAGRAM AND TYPICAL APPLICATION
+ SUPPLY V
DD
6
9V
I/O
2
V DD
FEEDBACK
8
11
HORN 2
3
LOW-V
SET
–
+
LOGIC
10
HORN 1
5
LED
+V
SENSITIVITY
SET
– SUPPLY
9
VSS
14
GUARD 1
DETECT. 15
IN
16
GUARD 2
1
TIMER
START
–
+
–
+
13
POWER-ON
RESET
TIMING RES.
7
OSCILLATOR
& TIMING
OSC. CAP.
12
4
TIMER OUT
+V
Dwg. FC-001-2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 1995, Allegro MicroSystems, Inc.
5347
SMOKE DETECTOR
with INTERCONNECT
and TIMER
ELECTRICAL CHARACTERISTICS at T
A
= +25
°
C, V
DD
= 9.0 V, V
SS
= 0 V, C
12
= 0.1
µ
F,
R
7
= 8.2 M
Ω
(unless otherwise noted).
Characteristic
Supply Voltage Range
Detector Input Current
Input Offset Voltage
Test
Pin
6
15
14-15
16-15
15-13
Hysteresis
Common Mode Range
13
14-15
13-15
Active Guard Impedance
14
16
Oscillator Period
12
Limits
Test Conditions
Operating
0 to 40% RH, V
IN
= 0 to 9.0 V
Active Guard
Active Guard
Detect Comparator
No Alarm to Alarm
Guard Amplifier
Smoke Comparator
to V
SS
to V
SS
No Alarm
Alarm
Oscillator Pulse Width
Timer Period
Low Voltage Threshold
Sensitivity Adj. Voltage
Horn Output Voltage
4
4
6
13
10-11
After Pin 1 High-to-Low, No Smoke
T
A
= 0 to 50°C
V
13
/V
DD
, pin 13 open circuit
I
OUT
= 16 mA, V
DD
= 9.0 V
I
OUT
= 16 mA, V
DD
= 7.2 V
I
OUT
= -16 mA, V
DD
= 9.0 V
I
OUT
= -16 mA, V
DD
= 7.2 V
Horn Output ON Time
10-11
Alarm
Low Battery
Horn Output OFF Time
10-11
Alarm
Low Battery
Timer Start Logic Levels
1
V
IH
V
IL
Timer Start Input Current
1
V
IN
= 9.0 V
Min.
6.0
—
—
—
—
90
2.0
0.5
—
—
1.34
32
8.0
8.0
7.2
48.5
—
—
8.5
6.3
120
8.0
60
32
3.5
—
20
Typ.
9.0
—
—
—
—
130
—
—
10
500
1.67
40
10
10
—
50
0.1
—
8.8
—
160
10
80
40
—
—
—
Max.
12
±1.0
±100
±100
±50
170
V
DD
- 0.5
V
DD
- 2.0
—
—
2.00
48
12
12
7.8
51.5
0.5
0.9
—
—
208
12
104
48
—
1.5
80
Units
V
pA
mV
mV
mV
mV
V
V
kΩ
kΩ
s
ms
ms
min
V
%
V
V
V
V
ms
ms
ms
s
V
V
µA
NOTE 1: Negative current is defined as coming out of (sourcing) the specified device pin.
NOTE 2: Alarm (Smoke) Condition is defined as V
15
< V
13
; No Alarm (No Smoke) Condition as V
15
> V
13
.
Continued next page . . .
5347
SMOKE DETECTOR
with INTERCONNECT
and TIMER
ELECTRICAL CHARACTERISTICS continued
Test
Pin
4
5
5
5
No Alarm, In Standby
No Alarm, Timer Mode After Pin 1
High-to-Low
I/O Current
2
No Alarm, V
I/O
= V
DD
- 2.0 V
Alarm, V
I/O
= V
DD
- 2.0 V
I/O Alarm Voltage
I/O Delay
Supply Current
2
2
6
External “Alarm” In
“Alarm” Out
V
DD
= 9.0 V, No Alarm, No Loads
V
DD
= 12 V, No Alarm, No Loads
NOTE 1: Negative current is defined as coming out of (sourcing) the specified device pin.
NOTE 2: Alarm (Smoke) Condition is defined as V
15
< V
13
; No Alarm (No Smoke) Condition as V
15
> V
13
.
Limits
Test Conditions
V
OUT
= 0.5 V
V
DD
= 7.2 V, V
OUT
= 1.0 V
Min.
500
10
8.0
32
8.0
25
-7.5
3.0
—
—
—
Typ.
—
—
10
40
10
—
—
—
3.0
5.0
—
Max.
—
—
12
48
12
60
—
—
—
9.0
12
Units
µA
mA
ms
s
s
µA
mA
V
s
µA
µA
Characteristic
Timer Out Output Current
LED Output ON Current
LED Output ON Time
LED Output OFF Time
CIRCUIT DESCRIPTION
The A5347CA is a low-current CMOS circuit providing all of the
required features for an ionization-type smoke detector.
Oscillator.
An internal oscillator operates with a period of 1.67
seconds during no-smoke conditions. Every 1.67 seconds, internal
power is applied to the entire circuit and a check is made for smoke.
Every 24 clock cycles (40 seconds), the LED is pulsed and a check
is made for low battery by comparing V
DD
to an internal reference.
Since very-low currents are used in the device, the oscillator capacitor
at pin 12 should be a low-leakage type (PTFE, polystyrene, or
polypropylene).
Detector Circuitry.
When smoke is detected, the resistor divider
network that sets the sensitivity (smoke trip point) is altered to increase
the sensitivity set voltage (pin 13) by typically 130 mV with no external
connections to pins 3 or 13. This provides hysteresis and reduces
false triggering. An active guard is provided on both pins adjacent to
the detector input (pin 15). The voltage at pins 14 and 16 will be within
100 mV of the input. This will keep surface leakage currents to a
minimum and provide a method of measuring the input voltage without
loading the ionization chamber. The active guard amplifier is not
power strobed and thus provides constant protection from surface
leakage currents. The detector input has internal diode protection
against static damage.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
5347
SMOKE DETECTOR
with INTERCONNECT
and TIMER
Alarm Circuitry.
If smoke is detected, the
oscillator period changes to 40 ms and the
horn is enabled. The horn output is typically
160 ms ON, 80 ms OFF. During the OFF
time, smoke is again checked and will inhibit
further alarm output if smoke is not sensed.
During smoke conditions the low battery
alarm is inhibited and the LED is driven at a
1 Hz rate.
Sensitivity Adjust.
The detector sensitivity
to smoke is set internally by a voltage divider
connected between V
DD
and V
SS
. The
sensitivity can be externally adjusted to the
individual characteristics of the ionization
chamber by connecting a resistor between
pin 13 and V
DD
, or between pin 13 and V
SS
.
Low Battery.
The low battery threshold is
set internally by a voltage divider connected
between V
DD
and V
SS
. The threshold can be
increased by connecting a resistor between
pin 3 and V
DD
. The threshold can be de-
creased by connecting a resistor between
pin 3 and V
SS
. The battery voltage level is
checked every 40 seconds during the 10 mA,
10 ms LED pulse. If an LED is not used, it
should be replaced with an equivalent
resistor (typically 500
Ω
to 1000
Ω)
such that
the battery loading remains at 10 mA.
Timer.
An internal timer is provided that can
be used in various configurations to allow for
a period of reduced smoke detector sensitiv-
ity (“hush”). When a high-to-low transition
occurs at pin 1, the internal timer is reset,
the timer mode enabled, and the circuit reset
to a no alarm condition. The LED will flash
at a 10 second rate. If the level of smoke is
increased such that the reduced sensitivity
level is reached, the device will go into the
alarm condition. The timer, however, will
continue to completion of the nominal 10-1/4
minute period (368 clock cycles). If the timer
mode is not used, pin 1 should be tied low.
TYPICAL APPLICATION
NOTE 4
50 kΩ
9V
TIMER
MODE
200 kΩ
200 kΩ
TO
OTHER
UNITS
1
200
Ω
2
NOTE
3
330
Ω
5
6
8.2 MΩ
7
1
µF
8
V
SS
V
DD
3
4
LOGIC
16
15
14
OSC. &
TIMING
13
12
11
10
9
0.1
µF
PUSH
TO
TEST
NOTE
1
HORN
DRIVER
1 MΩ
200 kΩ
0.001
µF
NOTE 2
Dwg. EC-005-2
NOTE 1: Use an external resistor to adjust sensitivity for a particular smoke
chamber.
NOTE 2: Select resistor to reduce sensitivity during timer mode.
NOTE 3: A resistor to ground or V
DD
may be added to this pin to modify low battery
voltage threshold.
NOTE 4: Reverse battery protection must be supplied externally.
I/O.
A connection is provided at pin 2 to allow multiple smoke detec-
tors to be commoned. If any single unit detects smoke (I/O is driven
high), all connected units will sound their associated horns after a
nominal 3 second delay. The LED is suppressed when an alarm is
signaled from an interconnected unit.
Testing.
On power up, all internal counters are reset. Internal test
circuitry allows for low battery check by holding pins 8 and 12 low
during power up, then reducing V
DD
and monitoring HORN
1
(pin 10).
All functional tests can be accelerated by driving pin 12 with a 2 kHz
square wave. The 10 ms strobe period must be maintained for proper
operation of the comparator circuitry.
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