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A5364CA Schematic ( PDF Datasheet ) - Allegro MicroSystems

Teilenummer A5364CA
Beschreibung Ionization Smoke Detector
Hersteller Allegro MicroSystems
Logo Allegro MicroSystems Logo 




Gesamt 9 Seiten
A5364CA Datasheet, Funktion
A5364
Ionization Smoke Detector
with Interconnect
Features and Benefits
Low average standby current for long battery life
Interconnect up to 125 detectors
Piezoelectric horn driver
Guard outputs for detector input
Pulse testing for low battery
Power-on reset (POR)
Internal reverse battery protection
Built-in hysteresis reduces false triggering
Temporal horn pattern, per UL217, NFPA72, and ISO8201
UL Recognized for UL217 applications, per file # S2113
Package: 16-pin DIP (suffix A)
Not to scale
Description
The A5364 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 their alarm. In addition, special features are incorporated
to facilitate alignment and test of the finished smoke detector.
The device is Recognized by Underwriters Laboratories for use
in smoke alarms that comply with Standard UL217.
The internal oscillator and timing circuitry keep standby power
to a minimum by powering down the device for 1.66 seconds
and sensing for smoke for only 10 ms. Every 24 on-off cycles,
a check is made for a 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 A5364 is supplied in a low-cost 16-pin dual in-line plastic
package (DIP). It is rated for continuous operation over the
temperature range of 0°C to 50°C. The Pb (lead) free version
(suffix –T) has 100% matte tin leadframe plating.
Typical Application
To / from
other units
200 Ω
B
1 NC
200 kΩ
16
GUARD2
2
I/O
15
DETECT IN
A5364
3
LOW-V SET
14
GUARD1
4 NC
330 Ω 5 LED
SENSITIVITY SET 13
12
OSC CAP
9V
6 VDD
11
HORN2
8.2 MΩ 7 TIMING RES
10
HORN1
1 μF 8 FEEDBACK
9
VSS
200 k Ω
Push
to Test
A
0.1 μF
A Use an external resistor to adjust
sensitivity for a particular smoke chamber.
B A resistor to VSS or VDD may
be added to this pin to modify
low battery voltage threshold.
C Value of component will vary, based on
the piezoelectric horn used.
1.5 MΩ
C
220 kΩ
C
0.001 μF
C
26110.7E






A5364CA Datasheet, Funktion
A5364
Ionization Smoke Detector
with Interconnect
of the ionization chamber by connecting a resistor between the
SENSITIVITY SET pin and either the VDD or VSS pins.
With no external connections on the SENSITIVITY SET pin,
while the A5364 is checking for smoke:
VSENSITIVITYSET = VDD / 2 .
To increase sensitivity, a resistor can be connected between
SENSITIVITY SET and VDD, with the value:
where
RSENSITIVITYSET = 1.1E6 × K / (1 – K) ,
K = VDD / VSENSITIVITYSET – 1 .
To decrease sensitivity, a resistor can be connected between
SENSITIVITY SET and VSS, with the value:
where
RSENSITIVITYSET = 1.1E6 × K / (1 – K) ,
K = 1 / (VDD / VSENSITIVITYSET – 1) .
Low Battery
The low battery condition threshold is set internally by a voltage
divider connected between VDD and VSS. The threshold can
be externally adjusted by connecting a resistor between the
LOW-V SET pin and either the VDD or VSS pins.
To increase the threshold, a resistor can be connected between
LOW-V SET and VSS. Given an initial threshold, V(th)init (nomi-
nally 7.5 V), and a target threshold, V(th)set, the resistor should
have the value:
where
RLOWVSET = 600E3 × K / (1 – 0.375 × K) ,
K = 1 / (V(th)set / [0.727 × V(th)init] – 1) .
To decrease the threshold, a resistor can be connected between
LOW-V SET and VDD. Given an initial threshold, V(th)init (nomi-
nally 7.5 V), and a target threshold, V(th)set, the resistor should
have the value:
where
RLOWVSET = 960E3 × K / (0.6 – 1.6 × K) ,
K = V(th)set / (0.727 × V(th)init) – 1 .
The battery voltage level is checked approximately every 40 sec-
onds during the (approximately) 10 mA, 10 ms LED pulse. If an
LED is not used, it should be replaced with an equivalent resistor
(typically 500 to 1000 Ω) such that the battery loading remains
about 10 mA.
I/O
A connection to the I/O pin allows multiple smoke detectors to
be interconnected. If any single unit detects smoke, its I/O pin is
driven high (after a nominal 3 s delay), and all connected units
will sound their associated horns. The LED is suppressed when
an alarm is signaled from an interconnected unit, and any local
alarm condition causes the I/O pin to be ignored as an input. This
pin has an on-chip pulldown device and must be left unconnected
if not used.
Testing
On power-up, all internal counters are reset. Internal test cir-
cuitry allows low battery check by holding the FEEDBACK and
OSC CAP pins low during power-up, then reducing VDD and
monitoring the HORN1 pin. HORN1 will be driven high when
VDD falls below the low-battery threshold. All functional tests
can be accelerated by driving the OSC CAP pin with a 2 kHz
square wave. The 10 ms strobe period must be maintained for
proper operation of the comparator circuitry.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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