a5354 Allegro MicroSystems, Inc., a5354 Datasheet - Page 5

• Manufacturer Part Number: a5354
• Description: Smoke Detector With Interconnect
• Manufacturer: Allegro MicroSystems, Inc.

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
sound their associated horns after a nominal
3 second delay. The LED is suppressed
when an alarm is signaled from an intercon-
nected 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
monitoring HORN
tests can be accelerated by driving pin 12
with a 2 kHz square wave. The 10 ms strobe
period must be maintained for proper opera-
tion of the comparator circuitry.
COMPARATOR
INTERNAL
CHAMBER
OSC. CAP
CLOCK
SMOKE
SMOKE
HORN
V12
LED
1.67 s
V15 > V13 (NO SMOKE)
SAMPLE
24 CLOCK CYCLES
1
LED OFF
NO LOW BATTERY
(pin 10). All functional
STANDBY MODE
NO ALARM
10 ms
DD
LED
ON
and
40 ms
HORN
ON
12 CLOCK CYCLES
OFF
NO LOW BATTERY
OTHER
ALARM
UNITS
TO
24 CLOCK CYCLES
9 V
NOTE 1: An external resistor divider is used to adjust sensitivity for the
NOTE 2: A resistor to ground or V
V15 < V13 (SMOKE)
NOTE
1 F
6 CLOCK CYCLES
200
2
8.2 M
330
particular smoke chamber.
low battery voltage threshold.
1
2
3
4
5
6
7
8
V
NC
NC
6 CLOCK CYCLES
DD
LOW BATTERY
DRIVER
ALARM AND
LOGIC
OSC. &
TIMING
HORN
with INTERCONNECT
200 k
DD
SMOKE DETECTOR
V
may be added to this pin to modify
SS
30 CLOCK CYCLES
16
15
14
13
12
11
10
9
0.1 F
LOW BATTERY
NO ALARM
0.001 F
Dwg. EC-005-4
LOW BATTERY
WARNING
5354
NOTE
PUSH
TEST
TO
1
Dwg. WC-003