A5349: AC Ionization Smoke Detector with Interconnect and Timer

A5349
AC Ionization Smoke Detector
with Interconnect and Timer
Features and Benefits
Description
▪ Low average standby current
▪ Interconnect up to 125 detectors
▪ Piezoelectric horn driver
▪ Guard outputs for detector input
▪ Pulse testing for low supply
▪ Power-on reset (POR)
▪ Internal reverse supply protection
▪ Timer (Hush) mode for enabling reduced sensitivity period
▪ Built-in hysteresis reduces false triggering
The A5349 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 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 supply 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
safety/security applications.
Package: 16-pin DIP (suffix A)
The A5349 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 –10°C to 60°C. The Pb (lead) free version
(suffix –T) has 100% matte tin leadframe plating.
Not to scale
Typical Application
Timer
Mode
200 kΩ
1
50 kΩ
200 Ω
To / from
other units
C
2
3
4
330 Ω
9V
1 μF
DETECT IN
I/O
A5349
LOW-V SET
GUARD1
TIMER OUT
5
7
8
LED
OSC CAP
VDD
HORN2
TIMING RES
HORN1
FEEDBACK
B
26110.4, Rev. 4
GUARD2
SENSITIVITY SET
6
8.2 MΩ
TIMER START
VSS
16
200 k Ω
15
Push
to Test
14
13
A
12
A Use an external resistor to adjust
sensitivity for a particular smoke chamber.
B Select resistor to reduce sensitivity
during Timer mode.
C A resistor to VSS or VDD may
be added to this pin to modify
low supply voltage threshold.
D Value of component will vary, based on
the piezoelectric horn used.
0.1 μF
11
10
9
1.5 MΩ
D
220 kΩ
D
0.001 μF
D
AC Ionization Smoke Detector
with Interconnect and Timer
A5349
Selection Guide
Part Number
Pb-Free
A5349CA-T
Packing
Yes
A5349CA
25 pieces per tube
–
Absolute Maximum Ratings*
Characteristic
Symbol
Notes
Rating
Units
V
Supply Voltage Range
VDD
Referenced to VSS
–0.5 to 15
Input Voltage Range
VIN
Referenced to VSS
–0.3 to VDD+ 0.3
V
Input Current
IIN
10
mA
Operating Ambient Temperature
TA
–10 to 60
ºC
TJ(max)
150
ºC
Tstg
–55 to 125
ºC
Junction Temperature
Storage Temperature Range
* CAUTION: CMOS devices have input static protection but are susceptible to damage when exposed to extremely high static electrical charges.
THERMAL CHARACTERISTICS
Characteristic
Symbol
RθJA
Package Thermal Resistance
Test Conditions*
Value Units
4-layer PCB based on JEDEC standard
38
ºC/W
*Additional thermal information available on Allegro website.
Terminal List Table
Number
Pin-out Diagram
TIMER START 1
I/O 2
16 GUARD2
15 DETECT IN
LOW-V SET 3
14 GUARD1
TIMER OUT 4
13 SENSITIVITY SET
1
Name
TIMER START
2
I/O
3
LOW-V SET
Optionally used with a resistor to adjust low-supply
threshold
4
TIMER OUT
Optionally used with a resistor to adjust sensitivity
during timer mode
LED
Output to drive visible LED
6
VDD
Positive supply voltage
7
TIMING RES
Terminal for timing resistor, sets internal bias
(affects timing)
Input for driving piezoelectric horn
LED 5
VDD 6
11 HORN2
8
FEEDBACK
TIMING RES 7
10 HORN1
9
VSS
10
HORN1
11
HORN2
9 VSS
Input/output to interconnected detectors
5
12 OSC CAP
FEEDBACK 8
Function
Input to start reduced sensitivity timer mode
12
OSC CAP
13
SENSITIVITY SET
14
GUARD1
15
DETECT IN
16
GUARD2
Negative supply voltage
Output for driving piezoelectric horn
Complementary output for driving piezoelectric horn
Terminal for charging/discharging an external
capacitor to run the oscillator
Optionally used with a resistor to adjust sensitivity
for a specific chamber
Active guard 1 for detector input
Input from detector chamber
Active guard 2 for detector input
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
AC Ionization Smoke Detector
with Interconnect and Timer
A5349
Functional Block Diagram
I/O
+Supply
9V
VDD
FEEDBACK
VDD
Band
Gap
LSSamp
HORN2
HORN1
Low Supply
Sample
Low Supply
Comparator
600 kΩ
_
LED
Logic
LOW-V SET
+ VDD
+
500 kΩ
Power-on
Reset
+
_
SENSITIVITY SET
SSamp
Smoke
Comparator
Smoke
Sample
1.1 MΩ
TIMING RES
LSSamp
SSamp
+ VDD
OSC CAP
Oscillator
and Timing
TIMER OUT
-Supply
VSS
+
_
GUARD1
DETECT IN
GUARD2
TIMER START
+ VDD
ION CHAMBER
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
AC Ionization Smoke Detector
with Interconnect and Timer
A5349
ELECTRICAL CHARACTERISTICS1,2 at TA = 25°C, VDD = 9.0 V, VSS = 0 V, COSCCAP = 0.1 μF,
RTIMINGRES = 8.2 MΩ (unless otherwise noted)
Characteristic
Supply Voltage Range
Supply Current
Detector Input Current
Symbol
VDD
IDD
Oscillator Pulse Width
IDETECTIN
VOS(GUARD1)
VOS(GUARD2)
VOS
VHYS
VCM(guard)
VCM
ZAG1
ZAG2
tosc
tosc(alarm)
tw(osc)
Timer Mode Duration
ttimer
Low-Supply Threshold
VDD(th)
Input Offset Voltage
Hysteresis
Common Mode Range
Active Guard Impedance
Oscillator Period
Sensitivity Adjust Voltage
VSET
VOL
Horn Output Voltage
VOH
Horn Output On-Time
Horn Output Off-Time
TIMER START Logic Levels
TIMER START Input Current
TIMER OUT Pulldown Current
LED Output-On Current
LED Output On-Time
LED Output Off-Time
ton(horn)
tw(horn)
toff(horn)
thorn
VIH
VIL
IIN
IPD
ILED
ton(LED)
tLED1
tLED2
tLED3
tLED4
Test Conditions
Operating
VDD = 9.0 V, no alarm, no loads
VDD = 12 V, no alarm, no loads
0% to 40% RH, VIN = 0 to 9.0 V
Active GUARD1
Active GUARD2
Detect comparator
No alarm to alarm
Guard amplifier
Smoke comparator
GUARD1 to VSS
GUARD2 to VSS
No alarm
Local or remote alarm
After TIMER START high-to-low,
no smoke
TA = 0°C to 50°C,
LOW-V SET open circuit
VSENSITIVITYSET / VDD,
SENSITIVITY SET open circuit
IOUT = 16 mA, VDD = 9.0 V
IOUT = 16 mA, VDD = 7.2 V
IOUT = –16 mA, VDD = 9.0 V
IOUT = –16 mA, VDD = 7.2 V
Local or remote alarm
Low supply
Local or remote alarm
Low supply
VTIMERSTART = 9.0 V
VTIMEROUT = 0.5 V
VDD = 7.2 V, VLED = 1.0 V
No alarm, timer mode
No alarm, in standby
No alarm, timer mode
Local alarm or test alarm
Remote alarm, no local smoke
Test Pin
6
6
6
15
14, 15
16, 15
15, 13
13
14, 15
13, 15
14
16
12
12
12
Min.
6.0
—
—
—
—
—
—
90
2.0
0.5
—
—
1.34
32
8.0
Typ.
9.0
5.0
—
—
—
—
—
130
—
—
10
500
1.67
40
10
Max.
12
9.0
12
±1.0
±100
±100
±50
170
VDD – 0.5
VDD – 2.0
—
—
2.00
48
12
Units
V
μA
μA
pA
mV
mV
mV
mV
V
V
kΩ
kΩ
s
ms
ms
4
8.0
10
12
min
6
7.2
—
7.8
V
13
48.5
50
51.5
%VDD
10, 11
10, 11
10, 11
10, 11
10,11
10, 11
10, 11
10, 11
1
1
1
4
5
5
5
5
5
5
—
—
8.5
6.3
120
8.0
60
32
3.5
—
20
500
10
—
—
—
—
—
0.1
—
8.8
—
160
10
80
40
—
—
—
—
—
8.35
Always on
1.67
Always off
Always on
0.5
0.9
—
—
208
12
104
48
—
1.5
80
—
—
—
—
—
—
—
V
V
V
V
ms
ms
ms
s
V
V
μA
μA
mA
s
s
s
s
s
Continued on the next page…
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
AC Ionization Smoke Detector
with Interconnect and Timer
A5349
ELECTRICAL CHARACTERISTICS1,2 (continued) at TA = 25°C, VDD = 9.0 V, VSS = 0 V, COSCCAP = 0.1 μF,
RTIMINGRES = 8.2 MΩ (unless otherwise noted)
Characteristic
Symbol
Test Conditions
Test Pin
Min.
Typ.
Max.
Units
No alarm, VI/O = VDD – 2.0 V
2
25
—
60
μA
IIOL
I/O Current
Local alarm, VI/O = VDD – 2.0 V
2
–7.5
—
—
mA
IIOH
I/O Alarm Voltage
VIH(IO)
External “alarm” in
2
3.0
—
—
V
I/O Delay
tr(io)
Local or test alarm to I/O active
2
—
3.0
—
s
1Negative current is defined as coming out of the specified device pin (sourcing).
2Alarm (smoke) condition is defined as V
DETECTIN < VSENSITIVITYSET; no alarm (no smoke) condition is defined as VDETECTIN > VSENSITIVITYSET.
Circuit Description
The A5349 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 seconds
during no-smoke conditions. Every 1.67 seconds, internal power
is applied to the entire circuit for 10 ms and a check is made for
smoke. Every 24 clock cycles (approximately 40 seconds), a
check is made for low supply by comparing VDD to an internal
reference. Because very-low currents are used in the device, the
oscillator capacitor at the OSC CAP pin should be a low-leakage
type (PTFE, polystyrene, or polypropylene).
Detector Circuitry
When the voltage on the DETECT IN pin is less than the voltage on the SENSITIVITY SET pin, the A5349 evaluates this as a
smoke condition. During a smoke condition, the resistor divider
network that sets the sensitivity (also referred to as the smoke trip
point) is altered to increase VSENSITIVITYSET by 130 mV typical
(with no external connections on the SENSITIVITY SET pin).
This provides hysteresis and reduces false triggering.
An active guard is provided on GUARD1 and GUARD2, the two
pins adjacent to the detector input, the DETECT IN pin. VGUARD1
and VGUARD2 will be within 100 mV of VDETECTIN. 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
electrostatic damage.
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 checked and further
alarm output will be inhibited if smoke is not sensed. During a
smoke condition, the low-supply alarm is inhibited and the LED
is turned off until the condition is removed.
Sensitivity Adjust
The detector sensitivity to smoke is set internally by a voltage
divider connected between VDD and VSS. The sensitivity can,
however, be externally adjusted to the individual characteristics
of the ionization chamber by connecting a resistor between the
SENSITIVITY SET pin and either the VDD or VSS pins.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
AC Ionization Smoke Detector
with Interconnect and Timer
A5349
With no external connections on the SENSITIVITY SET pin,
while the A5349 is checking for smoke:
VSENSITIVITYSET = VDD / 2 .
To increase sensitivity, a resistor can be connected between
SENSITIVITY SET and VDD, with the value:
RSENSITIVITYSET = 1.1E6 × K / (1 – K) ,
where
K = VDD / VSENSITIVITYSET – 1 .
To decrease sensitivity, a resistor can be connected between
SENSITIVITY SET and VSS, with the value:
RSENSITIVITYSET = 1.1E6 × K / (1 – K) ,
where
K = 1 / (VDD / VSENSITIVITYSET – 1) .
Low Supply
The low supply 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 (nominally 7.5 V), and a target threshold, V(th)set , the resistor should
have the value:
RLOWVSET = 600E3 × K / (1 – 0.375 × K) ,
where
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 (nominally 7.5 V), and a target threshold, V(th)set , the resistor should
have the value:
RLOWVSET = 960E3 × K / (0.6 – 1.6 × K) ,
where
K = V(th)set / (0.727 × V(th)init) – 1 .
The supply voltage level is checked approximately every 40
seconds.
Timer (Hush) Mode
An internal timer is provided that can be used in various configurations to allow a period of reduced smoke detector sensitivity,
referred to as Timer (or Hush) mode.
In normal operation, when a high-to-low transition occurs at the
TIMER START pin, the internal timer is reset, Timer mode is
enabled, and the circuit resets to a no-alarm condition. During
Timer mode, which is active for approximately 10.25 minutes
(368 clock cycles), the TIMER OUT pin is pulled down to VSS
every time the A5349 makes a check for smoke. A resistor connected between the TIMER OUT and the SENSITIVITY SET
pins will decrease the detector’s sensitivity to smoke during
this time, and allow the user to hush alarms caused by nuisance
smoke or steam (such as from cooking). At the end of Timer
mode, the device signals its completion with two 10-ms horn
chirps, 1.67 seconds apart.
While the Timer mode is active, the LED blinks, remaining on
for approximately 8.7 s and off for approximately 1.67 s. If the
level of smoke increases such that the reduced-sensitivity level
is reached, the A5349 will signal an Alarm condition. If such an
Alarm condition does occur, the timer will still continue to completion of its cycle. If Timer mode will not be used, the TIMER
START pin should be tied to VSS.
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 remains on constantly
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.
When in Timer mode, the device will still signal an alarm if I/O is
driven high externally. 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 circuitry allows low supply 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-supply 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
6
AC Ionization Smoke Detector
with Interconnect and Timer
A5349
Timing Diagrams
(Not to scale)
Test event
Standby Mode
OSC CAP Pin
tosc
tw(osc)
Internal Clock
Smoke Sample
Low Supply Test
LED Pin
LED on
Timer Mode
Internal Clock
tosc
tw(osc)
TIMER START Pin
ttimer
TIMER OUT Pin
Output off (High Z)
tled2
t off (led)
LED off (high-Z)
LED Pin
LED on
Horn Enable
Low Supply Condition
(Low supply)
VDD Pin
Low SupplyTest
LED Pin
LED on
thorn
tw(horn)
Horn Enable
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
7
AC Ionization Smoke Detector
with Interconnect and Timer
A5349
Local Smoke Detection/Test Alarm Condition
Test event
tosc(alarm)
tw(osc)
OSC CAP Pin
Internal Clock
Smoke Sample
6 clock cycles
Smoke Sample
Smoke Chamber
(no smoke )
VDETECTIN < V SENSITIVITYSET (smoke)
LED Pin
LED off (high-Z)
ton(horn)
toff(horn)
Horn Enable
tr(io)
(Output)
I/O Pin
Remote Alarm Condition
tosc(alarm)
OSC CAP Pin
Internal Clock
I/O Pin
tw(osc)
LED on
LED Pin
ton(horn)
toff(horn)
Horn Enable
I/O Pin
(Input)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
8
AC Ionization Smoke Detector
with Interconnect and Timer
A5349
Package A, 16-Pin DIP
.750 [19.05]
16
.010 [0.25]
.250 [6.35]
.430 [10.92]
.300 [7.62]
A
1
2
.210 [5.33] MAX
.130 [3.30]
.100 [2.54]
.005 [1.27]
.060 [1.52]
All dimensions nominal, not for tooling use
(reference JEDEC MS-001 BB)
Dimensions in inches, metric dimensions (mm) in brackets, for reference only
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
.018 [0.46]
Allegro MicroSystems offers an industry-leading range of ionization
and photoelectric smoke detector ICs. For a current listing, please visit
our website at:
www.allegromicro.com
Copyright ©1995-2009, Allegro MicroSystems, Inc.
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’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the
failure of that life support device or system, or to affect the safety or effectiveness of that device or system.
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.
For the latest version of this document, visit our website:
www.allegromicro.com
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
9
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