Allegro A5338 Smoke detector with interconnect and timer Datasheet

A5338
Smoke Detector
with Interconnect and Timer
Package A, 16-lead DIP
The A5338CA is a low-current, CMOS circuit
providing all of the required features for an ionizationtype 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 A5338CA 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.
Approximate Scale 1:1
Features
Interconnect up to 125 detectors
Piezoelectric horn driver
Guard outputs for detector input
Pulse testing for low battery
Power-on reset
Internal reverse battery protection
Internal timer and control for reduced sensitivity
Built-in hysteresis reduces false triggering
Typical Application
9V
200 kΩ
50 kΩ
200 kΩ
Push to set
1
To other units
200 Ω
2
3
+SUPPLY or
–SUPPLY
RLV
I/O
5
6
RT
8.2 MΩ
1 μF
7
8
16
Push to test
Smoke
Chamber
DETECT IN 15
A5338
LOW-V SET
4 TIMER OUT
330 Ω
GUARD2
TIMER START
GUARD1 14
SENSIVITIVTY SET
OSC CAP
LED
13
RS
12
+SUPPLY or
–SUPPLY
11
+SUPPLY
HORN2
TIMING RES
HORN1 10
–SUPPLY
FEEDBACK
COSC
0.1 μF
Horn
9
1 MΩ
200 kΩ
0.001 μF
RST
Dwg. EC-005A
26110.1
A5338
Smoke Detector with Interconnect and Timer
Functional Block Diagram
I/O
+SUPPLY
VDD
VDD
FEEDBACK
HORN2
HORN1
–
LOW-V SET
+
LED
Logic
SENSITIVITY SET
+
Power-On
Reset
–
TIMING RES
–
–SUPPLY
OSC CAP
Oscillator
and Timing
+
TIMER OUT
VSS
GUARD1
DETECT IN
TIMER START
GUARD2
Selection Guide
Part Number
Package
Packing
A5338CA
16-pin DIP, 300 mil spacing
25 pieces per tube
Absolute Maximum Ratings1
Parameter
Supply Voltage
Range2
Symbol
Conditions
VDD
Typ.
Max. Units
–0.5
–
15
V
–
–
20
s
VDD
+ 0.3
V
10
mA
Reverse Battery
–
Logic Input Voltage Range2
VI
–0.3
Logic Input Current
II
–
–
Operating Temperature Range (C)
TA
0
–
50
°C
Junction Temperature
TJ
–
–
150
°C
Storage Temperature Range
TS
–55
–
125
°C
1CMOS
10.5 V
Min.
devices have input static protection, but are susceptible to damage when exposed to extremely high static electrical charges.
are references to VSS.
2Voltages
2
26110.1
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A5338
Smoke Detector with Interconnect and Timer
Pin-out Diagram
TIMER START
1
I/O
2
LOW-V SET
3
TIMER OUT
4
LED
5
+SUPPLY
6
TIMING RES
7
FEEDBACK
8
LOGIC
OSC. &
TIMING
V DD
HORN
DRIVER
V SS
16
GUARD2
15
DETECT IN
14
GUARD1
13
SENSITIVITY SET
12
OSC CAP
11
HORN2
10
HORN1
9
–SUPPLY
Dwg. PC-004
Terminal List Table
Number
Name
1
TIMER START
2
I/O
3
LOW-V SET
4
TIMER OUT
5
LED
6
+SUPPLY
7
TIMING RES
8
FEEDBACK
9
–SUPPLY
Device supply, VSS.
10
HORN1
Horn driver output 1.
Horn driver output 2.
11
HORN2
12
OSC CAP
13
SENSITIVITY SET
14
GUARD1
15
DETECT IN
16
GUARD2
Function
Logic input for setting device mode.
Logic input/output, where multiple detectors can be connected.
Terminal for a resistor, RLV, to the –SUPPLY pin (VSS) or to the +SUPPLY pin (VDD),
which may be added to modify the battery Low Voltage Threshold, VDDL.
Terminal for a resistor, RST, to reduce sensitivity during Timer mode.
LED output.
Device supply, VDD.
Terminal for timing resistor.
Feedback from horn external circuit.
Terminal for timing oscillator capacitor.
Terminal for resistor, RS, to adjust sensitvity for a particular smoke chamber.
Terminal for smoke detector guard 1.
Terminal for smoke detector input.
Terminal for smoke detector guard 2.
3
26110.1
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A5338
Smoke Detector with Interconnect and Timer
ELECTRICAL CHARACTERISTICS1 at TA = 25°C, VDD = 9.0 V, VSS = 0 V, COSC = 0.1 μF, RT = 8.2 MΩ, unless otherwise noted
Characteristic
Supply Voltage Range
Symbol
VDD
Supply Current
IDD
Detector Input Current2
IS
Input Offset Voltage
Hysteresis
Common Mode Range
VIO
VOhys
Test Pin
Test Conditions
6
Operating
VDD = 9.0 V, no alarm, no loads
6
VDD = 12 V, no alarm, no loads
15
0 to 40% RH, VI(detect in) = 0 to 9.0 V
14-15 Active guard
16-15 Active guard
15-13 Smoke detect comparator
13
No alarm condition to alarm
Min.
6.0
—
—
–1.0
–100
–100
–50
90
Typ.
9.0
5.0
—
—
—
—
—
130
VIC(guard)
14-15
Guard amplifier
2.0
—
VIC(det)
13-15
Smoke detect comparator
0.5
—
—
10
—
500
1.34 1.67
Oscillator Period
tOSC
12
32
40
Oscillator Pulse Width
tw(osc)
4
8.0
10
Timer Period
ttimer
4
After VTIMER_START transition high-to-low (smoke detected)
5.0
6.5
Low Voltage Threshold
VDD(th)
6
TA = 0 to 50°C
7.2
—
Sensitivity Adjust Voltage
VS
13
VSENSITIVITY_SET/VDD, SENSITIVITY SET pin open circuit
48.5
50
IO(horn) = 16 mA, VDD = 9.0 V
—
0.1
—
—
IO(horn) = 16 mA, VDD = 7.2 V
HORNx Output Voltage
VO(horn)
10-11
IO(horn) = –16 mA, VDD = 9.0 V
8.5
8.8
IO(horn) = –16 mA, VDD = 7.2 V
6.3
—
Alarm
120
160
HORNx Output ON Time
ton(horn)
10-11
Low battery
8.0
10
Alarm
60
80
HORNx Output OFF Time
toff(horn)
10-11
Low Battery
32
40
1
4.5
—
VIH(ts)
TIMER START Logic Levels
VIL(ts)
1
—
—
TIMER START Input Current
II(ts)
1
VI(ts) = 9.0 V
20
—
TIMER OUT Output Current
IO(to)
4
VO(to) = 0.5 V
500
—
LED Output ON Current
ILED
5
VDD = 7.2 V, VLED = 1.0 V
10
—
LED Output ON Time
ton(led)
5
8.0
10
No alarm; in Standby mode
32
40
LED Output OFF Time
toff(led)
5
No alarm; in Timer mode after VTIMER_START transition high-to-low
8.0
10
2
No alarm, V(IO) = VDD - 2.0 V
25
—
I/O Current2
I(io)
-7.5
—
Alarm, V(IO) = VDD - 2.0 V
Charge dump, V(io) = 1.0 V
5.0
—
I/O Charge Dump Duration
tf(io)
2
After local alarm
1.33 1.66
2
External alarm signal in
3.0
—
I/O Alarm Voltage
VI(io)
I/O Delay
td(io)
2
Alarm signal out
—
3.0
1Alarm (smoke detected) condition is defined as V
DETECT_IN < VSENSITIVITY_SET; No-Alarm (no smoke detected) condition is defined as
VDETECT_IN > VSENSITIVITY_SET.
2Negative current is defined as coming out of (sourcing) the specified device pin.
Active Guard Impedance
Zguard
14
16
With reference to VSS
With reference to VSS
No alarm
Alarm
Max.
12
9.0
12
1.0
100
100
50
170
VDD
- 0.5
VDD
- 2.0
—
—
2.00
48
12
8.0
7.8
51.5
0.5
0.9
—
—
208
12
104
48
—
2.5
80
—
—
12
48
12
60
—
—
1.99
—
—
Units
V
μA
μA
pA
mV
mV
mV
mV
V
V
Ω
Ω
s
ms
ms
min
V
%
V
V
V
V
ms
ms
ms
s
V
V
μA
μA
mA
ms
s
s
μA
mA
mA
s
V
s
4
26110.1
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A5338
Smoke Detector with Interconnect and Timer
Functional Description
The A5338 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 s
during no-smoke conditions. Every 1.67 s, internal power is
applied to the entire circuit and a check is made for smoke. Every
24 oscillator cycles (40 s total), the LED is pulsed and a check is
made for low battery by comparing VDD to an internal reference.
Because very low currents are used in the device, the oscillator
capacitor, COSC, at the OSC CAP pin 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 voltage on the SENSITIVITY SET pin by
130 mV typical, when there are no external connections to the
SENSITIVITY SET pin or LOW-V SET pin. This provides hysteresis and reduces false triggering. An active guard is provided
on both GUARDx pins, adjacent to the DETECT IN detector input pin. The voltage at the GUARDx pins will be within
100 mV of DETECT IN. 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.
Alarm Circuitry. If smoke is detected, the oscillator period
changes to 40 ms and the horn is enabled. The horn output is 160
ms ON, and 80 ms OFF, typical. During the OFF time, smoke is
again checked and the circuit will inhibit further horn output if
smoke is not sensed. During smoke conditions, the low-batterywarning is inhibited. The LED is driven at a 1 Hz rate, and will
only turn ON while the horn outputs are in the OFF state.
Sensitivity Adjust. The detector sensitivity to smoke is set
internally by a voltage divider connected between VDD and VSS.
The sensitivity can be externally adjusted to the individual characteristics of the ionization chamber by connecting a resistor, RS,
between the SENSITIVITY SET pin and +SUPPLY, or between
SENSITIVITY SET pin and –SUPPLY.
Low Battery. The low-battery threshold is set internally by a
voltage divider connected between VDD and VSS. The threshold
can be increased by connecting a resistor, RLV, between the
LOW-V SETpin and +SUPPLY. The threshold can be decreased
by connecting RLV between LOW-V SETpin and –SUPPLY. The
battery voltage level is checked every 40 s during the 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 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
sensitivity, Hush mode. When a high-to-low transition occurs at
the TIMER START pin, the internal timer is reset, Timer mode is
enabled, and the circuit is reset to a no-alarm condition. During Hush mode, the LED will flash at a 10 s 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 6.5 minute
period (232 oscillator cycles). If Timer mode is not used, the
TIMER START pin should be tied low. While in Hush mode, the
battery is checked. If a low-battery condition is detected, the lowbattery warning chirp will be activated.
I/O. The I/O pin provides a terminal 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 s delay. The LED is suppressed when an
alarm is signaled from another interconnected unit. An internal NMOS device acts as a charge dump to aid in applications
involving a large (distributed) capacitance on the I/O pin. The
charge dump is activated only on the removal of a local alarm.
Testing. On power-up, all internal counters are reset. Internal
test circuitry allows for low-battery check by holding the
FEEDBACK and OSC CAP pins low during power-up, then
reducing VDD and monitoring HORN1. All functional tests can be
accelerated by driving OSC CAP with a 2 kHz square wave. The
10 ms strobe period must be maintained for proper operation of
the comparator circuitry.
5
26110.1
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A5338
Smoke Detector with Interconnect and Timer
Timing Requirements: Nontimer Mode
(Circuit Shown in Typical Application)
10 ms
1.67 s
40 ms
Internal
Oscillator
24 Cycles
LED
24 Cycles
30 Cycles
LED Off
LED On
12 Cycles
6 Cycles
6 Cycles
Internal
Smoke
Comparator
Ssmple
HORN On
Low Battery
Warning
HORNx
HORN Off
Smoke
Chamber
Condition
VDETECT_IN < VSENSITIVITY_SET
(smoke)
VDETECT_IN > VSENSITIVITY_SET
(no smoke)
VDETECT_IN > VSENSITIVITY_SET
(no smoke)
Dwg. WC-003
Timing Requirements: Timer Mode
(Circuit Shown in Typical Application)
OSC CAP
1.67 s
10 ms
Internal
Oscillator
232 Cycles
TIMER START
TIMER OUT
6 Cycles
Outputs Off (High Z)
LED
Dwg. WC-005-3
LED On
6
26110.1
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A5338
Smoke Detector with Interconnect and Timer
I/O Operation: V(IO) Input
Remote Alarm Mode
1.67 s
40 ms
Internal
Oscillator
4 Cycles
HORNx
2 Cycles
HORN On
HORN Off
I/O
HORN not self-completing
when in remote-only alarm
I/O Operation: V(IO) Output
Local Alarm Mode
Internal
Oscillator
HORN On
HORNx
HORN Off
78 Cycles
I/O
Dwg. WC-004
7
26110.1
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A5338
Smoke Detector with Interconnect and Timer
Package A, 16-pin DIP
.775 19.69
.735 18.67
A
.014 0.36
.008 0.20
B
16
.280 7.11
.240 6.10
.300 .7.62
.430 10.92
MAX
A
1
2
.195 4.95
.115 2.92
.015 2.92
MIN
.005 0.13
MIN
.070 1.78
.045 1.14
.100 .2.54
16X
.022 .056
.014 .036
.150 3.81
.115 2.92
SEATING
PLANE
C
Preliminary dimensions, for reference only
Dimensions in inches
Metric dimensions (mm) in brackets, for reference only
(reference JEDEC MS-001 BB)
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
A Terminal #1 mark area
.010 [0.25] M C
The products described here are manufactured under one or more U.S. patents or U.S. patents pending.
Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit
improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the
information being relied upon is current.
Allegro products are not authorized for use as critical components in life-support devices or systems without express written approval.
The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use;
nor for any infringement of patents or other rights of third parties which may result from its use.
Copyright©2005 AllegroMicrosystems, Inc.
8
26110.1
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com