Description
The A5358 is a low-current BiCMOS circuit providing all of
the required features for a photoelectric type smoke detector.
This device can be used with an infrared photoelectric chamber
to sense scattered light from smoke particles. A networking
capability allows as many as 50 units to be interconnected so
that if any unit senses smoke all units will sound an alarm.
Special features are incorporated in the design to facilitate
calibration and testing of the finished detector. The device is
designed for applications that comply with European Standard
EN 14604 and British Standard BS 5446, Part 1.
A variable-gain photoamplifier can be directly interfaced to
an infrared emitter-detector pair. The amplifier gain levels are
determined by two external capacitors and are internally selected
depending on the operating mode. Low gain is selected during
standby and timer modes. During a local alarm, this low gain
is increased (internally) by approximately 10% to reduce false
triggering. High gain is used during pushbutton test and to
periodically monitor the chamber sensitivity during standby.
The internal oscillator and timing circuitry keep standby power
to a minimum by sensing for smoke for only 100 s every 10 s.
A special three-stage–speedup sensing scheme is incorporated
to minimize the time to an audible alarm and also to reduce
false triggering. Chamber sensitivity is periodically monitored
and two consecutive cycles of degraded sensitivity are required
for a warning signal (chirp) to occur.
The A5358 is supplied in a 16-pin dual in-line plastic package
(suffix A), and for surface mount, a 16-pin SOICW (suffix
LW). The lead (Pb) free versions (suffix –T) have 100% matte-
tin leadframe plating. The devices are rated for continuous
operation over the temperature range of –25°C to 75°C.
26110.10-DS, Rev. I
Features and Benefits
Low average standby current for long battery life
Interconnect up to 50 detectors
Piezoelectric horn driver
Low battery detection (all internal)
Chamber sensitivity test and alarm
Power-on reset (POR)
Internal timer and control for reduced sensitivity mode
Built-in circuits to reduce false triggering
6 to 12 V operating range
ESD protection circuitry on all pins
Photoelectric Smoke Detector
with Interconnect and Timer
Packages:
Not to scale
A5358
16-pin DIP
(Package A)
16-pin SOICW
(Package LW)
Typical Application Diagram
C1
C2
DETECT
STROBE
VDD
IRED
HORN1
HORN2
I/O
FEEDBACK
LED
OSC CAP
TIMING RES
VSS
HUSH
TEST
A5358
To / from
other units
220
Rx2
Rx1
100 F
1 k
4.7 k
5 k
4700 pF
0.047 F
560
200 k
220 k
1.5 M
1000 pF
100 k
10 M
330
1500 pF
Red LED
Push-to-Test
9 V
22 F
Connect HUSH to VSS
to disable timer mode
Value of component can vary,
based on the piezoelectric horn used
Connect to allow timer mode
("hush") operation
Piezo Horn
8.2 k
V
DD
22
Smoke
Chamber
B
C
C
C
C
B
A
A
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
