A5349CA ALLEGRO [Allegro MicroSystems], A5349CA Datasheet - Page 5

• Manufacturer Part Number: A5349CA
• Description: AC SMOKE DETECTOR WITH INTERCONNECT AND TIMER
• Manufacturer: ALLEGRO [Allegro MicroSystems]

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-supply
alarm is inhibited.
LED. The LED is continuously ON during the
standby mode indicating the unit is receiving
power. During a remote alarm condition the
LED remains ON. The LED is OFF during a
local alarm condition.
Sensitivity Adjust. The detector sensitivity
to smoke is set internally by a voltage divider
connected between V
sensitivity can be externally adjusted to the
individual characteristics of the ionization
chamber by connecting a resistor between
pin 13 and V
Low Supply. The low supply threshold is set
internally by a voltage divider connected
between V
increased by connecting a resistor between
pin 3 and V
creased by connecting a resistor between pin
3 and V
checked every 40 seconds.
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 in-
creased 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.
I/O. A connection is provided at pin 2 to
allow multiple smoke detectors to be
commoned. If any single unit detects smoke
(I/O is driven high), all connected units will
5349
AC SMOKE DETECTOR
with INTERCONNECT
and TIMER
SS
. The supply voltage level is
DD
DD
DD
and V
. The threshold can be de-
, or between pin 13 and V
SS
. The threshold can be
DD
and V
SS
. The
SS
.
sound their associated horns after a nominal 3 second delay. The LED
remains ON when an alarm is signaled from an interconnected unit
and a local smoke condition does not exist.
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
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.
+ SUPPLY
NOTE 1: Use an external resistor to adjust sensitivity for a particular
NOTE 2: Select resistor to reduce sensitivity during timer mode.
NOTE 3: A resistor to ground or V
NOTE 4: Reverse supply protection must be supplied externally.
OTHER
UNITS
TO
smoke chamber.
voltage threshold.
NOTE
TIMER
MODE
1 F
200
3
8.2 M
330
1
2
3
4
5
6
7
8
TYPICAL APPLICATION
V
DD
NOTE 2
LOGIC
DRIVER
OSC. &
TIMING
HORN
DD
may be added to this pin to modify low battery
DD
200 k
and monitoring HORN
V
SS
16
15
14
13
12
11
10
9
0.1 F
1
(pin 10).
Dwg. EC-005-1A
NOTE
PUSH
TEST
TO
1
0.001 F