A5303 Datasheet

A5303
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
Features and Benefits
▪Low average standby current allows 10-year battery life
▪2.3 to 5.5 V operating range
▪Interconnect option
▪Logic outputs to control an external sound IC
▪Low battery detection and warning
▪Chamber sensitivity test and warning
▪Triple horn-chirp to distinguish chamber warning
▪Power-on reset (POR)
▪Digital filter on I/O provides significant noise immunity
▪Timer (hush) mode for enabling reduced sensitivity period
▪Built-in circuits to reduce false triggering
▪ESD protection circuitry on all pins
▪Temporal Horn Pattern, per UL217, NFPA72, ISO8201
▪Latching alarm indicator identifies alarm-initiating devices
Packages:
20-pin TSSOP
(LE package)
Not to scale
Description
The A5303 is a low-current BiCMOS photoelectric smoke
detector circuit with ultra-low standby current and can operate
for 10 years powered by inexpensive batteries. This device can
be used with an infrared optical chamber to sense light scattered
from smoke particles. A networking capability allows 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.
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 45% to provide
hysteresis. High gain is used during pushbutton test and to
periodically monitor the chamber sensitivity during standby.
The internal oscillator and timing circuitry minimize standby
power by sensing for smoke for only 100 μs once 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 to occur.
The A5303 is supplied in a thin profile (<1.2 mm overall height)
20-pin TSSOP (LE) package (0.65 mm nominal lead pitch)
and a 20-contact QFN (ES) package with exposed thermal
pad. Both packages are lead (Pb) free with 100% matte tin
leadframe plating.
20-contact QFN
4 mm × 4 mm × 0.75 mm
(ES package)
Typical Application Diagram
To / from
other units
56 nF
C1
R1
3 kΩ
5.6 nF
560 Ω
Connect to allow timer (hush) mode operation
C2
5 kΩ
220 Ω
VDD
I/O
VDD
Gain
Select
Low Batt
DETECT
VDD
1 kΩ
STROBE
VDD 1.6 V
Control
Logic
ISET
HUSH
VSS
B
SOUT0
SOUT1
SOUT2
Voice IC outputs
HORN
Output to optional
boost converter to
drive a piezo horn
LED
3Ω
Connect HUSH to
VSS to disable
timer mode
Push-to-test
BLINK
IRED
100 µF
Low Batt
Sample
TEST
R2
Smoke
Chamber
OSC
Timing
Red LED
OSCCAP
1500 pf
TRES
100 kΩ
5303-DS, Rev. 1
10 µF
A
LVSET
200 kΩ
3V
VDD
1.2 V
VDD
10 ΜΩ
A
A resistor connected
between this pin and
VDD or VSS adjusts
the low-battery threshold
B
In standby, BLINK = VDD
causes LED to blink,
BLINK = V SS causes
LED not to blink
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
A5303
Selection Guide
Part Number
A5303SESTR-T
A5303SLE-T
A5303SLETR-T
Pb-free and RoHS
Yes
Yes
Yes
Package
20-contact QFN
20-pin TSSOP (JEDEC MO-153AC)
20-pin TSSOP (JEDEC MO-153AC)
Packing
1500 pieces / 7-in. reel
75 pieces / tube
4000 pieces / reel
Absolute Maximum Ratings
Characteristic
Symbol
Notes
Rating
Units
–2.3 to 6
V
Supply Voltage Range
VDD
Referenced to VSS
DC Input Voltage Range
VIN
Referenced to VSS
–0.3 to 6
V
Operating Ambient Temperature Range
TA
Allegro Range S
–20 to 85
ºC
TJ(max)
150
ºC
Tstg
–55 to 150
ºC
Maximum Junction Temperature
Storage Temperature Range
Thermal Characteristics
Characteristic
Symbol
Package Thermal Resistance
Test Conditions*
RθJA
Value
Units
ES Package, 4-layer PCB, based on JEDEC standard
37
ºC/W
LE Package, estimated, single-layer PCB, minimal exposed copper area
127
ºC/W
*Additional thermal information available on Allegro website.
Terminal List
Number
16 IO
17 BLINK
18 HUSH
19 ISET
20 VDD
Pin-out Diagram
Name
Function
ES
LE
14
1
SOUT1
Logic push-pull output for controlling an external sound IC
15
2
SOUT0
Logic push-pull output for controlling an external sound IC
16
3
I/O
17
4
BLINK
Logic input for enabling/disabling the LED blink during standby
Input for photoamplifier timer mode reference; can also disable timer mode
IRED
1
15
SOUT0
STROBE
2
14
SOUT1
DETECT
3
13
SOUT2
C2
4
12
LED
18
5
HUSH
C1
5
11
HORN
19
6
ISET
A resistor on this pin connected to VSS sets the IRED output current
20
7
VDD
Positive supply voltage
1
8
IRED
Terminal to drive smoke chamber IR LED
2
9
STROBE
Strobed supply (VDD – 2 V) for photoamplifier low-side reference
3
10
DETECT
Photoamplifier input
4
11
C2
Sets photoamplifier gain in standby mode
5
12
C1
Sets photoamplifier gain in supervisory mode
18 HORN
6
13
LVSET
Optionally used with a resistor to adjust the low-battery threshold
BLINK 4
17 TEST
7
14
TRES
Connection for resistor to set clock times/frequency
HUSH 5
16 OSC CAP
8
15
VSS
TEST 10
OSC CAP 9
8
VSS
7
TRES
LVSET 6
PAD
ES Package
SOUT1 1
20 SOUT2
SOUT0 2
19 LED
I/O 3
Input-output to interconnected detectors
Negative supply voltage
ISET 6
15 VSS
VDD 7
14 TRES
9
16
OSC CAP
IRED 8
13 LVSET
10
17
TEST
Enables push-to-test mode; starts timer mode, if enabled
Logic output which optionally enables a boost converter to drive a horn
STROBE 9
12 C1
DETECT 10
11 C2
LE Package
11
18
HORN
12
19
LED
13
20
SOUT2
PAD
–
–
Connection for capacitor and resistor to set clock times/frequency
Output to drive visible LED
Logic push-pull output for controlling an external sound IC
Exposed pad for enhanced thermal dissipation
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
A5303
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
DC ELECTRICAL CHARACTERISTICS1 Valid at TA = 25°C, VDD = 2.3 to 5.5 V, configured as in Typical Application Diagram
(unless otherwise noted)
Characteristics
Symbol
Supply Voltage Range
VDD
Operating Supply Current
IDD
Input Current
TEST Pulldown Current
IIN
IIN(TEST)
Test Conditions
Operating
Min.
Typ.2
Max.
Unit
2.3
3.0
5.5
V
During standby, STROBE off
–
2.3
5.0
μA
During STROBE on, IRED off
–
210
300
μA
During STROBE on, IRED on
–
220
300
μA
–100
0
100
nA
–
3.5
–
μA
V
BLINK, C1, C2, DETECT, OSC CAP, TRES
(pulldown off)
VTEST = VDD = 3 V
Logic Voltage Low
VI(L)
–
–
VDD ×
0.3
Logic Voltage High
VI(H)
VDD ×
0.7
–
–
V
Strobe Output Voltage
VST
Inactive
Line Regulation
Strobe Temperature Coefficient
Maximum IRED Current Setting
–
VDD
–
V
VDD –
2.1
VDD –
2.0
VDD –
1.9
V
–
–60
–
dB
VSTROBE, VDD = 2.3 to 5.5 V
–
0.01
–
% / °C
Current is set by selection of resistor on ISET
pin
–
–
300
mA
89
100
111
mA
Active, IO = 100 to 500 μA
ΔVST(ΔVDD) Active, VDD = 2.3 to 5.5 V
αST
IIRED(MAX)
IRED Current
IIRED
RISET = 3 Ω
IRED Temperature Coefficient
αIRED
IIRED, VDD = 2.3 to 5.5 V
–
0.40
–
% / °C
ILED
VLED = 0.5 V
0.6
1.2
1.8
mA
Low-Battery Warning Threshold
VDD(th)
LVSET open
2.4
2.5
2.6
V
Low-Battery Warning Minimum
VDD(warn)
VDD –
1.0
–
VDD –
0.3
V
LED Drive Current
Common Mode Voltage
VIC
VDD voltage guaranteed to operate SOUTx pins
Photoamplifier input
1.8
V
Smoke Comparator Reference Voltage
VREF
Any alarm condition, except hush mode
–
VDD –
1.6
–
V
I/O Input Impedance
ZI/O(in)
No alarm conditions
40
83
–
kΩ
I/O Output Impedance
ZI/O(out)
Local or test alarm
–
3.9
5.7
kΩ
1Limits
over the operating temperature range are based on characterization data. Characteristics are production tested at 25°C only.
2Typical values are at 25°C and are given for circuit design information only.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
A5303
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
AC ELECTRICAL CHARACTERISTICS1 Valid at TA = 25°C, VDD = 2.3 to 5.5 V, configured as in Typical Application Diagram
(unless otherwise noted)
Characteristics
Oscillator Period
Smoke Check
Low Battery Test
Degraded Chamber Test
LED Pulse Period
Symbol
Typ.2
Max.
Unit
1
9.4
10.5
11.5
ms
210
9.6
10.75
11.9
s
min
tbattery
No low-battery detected
218
41.3
45.9
50.5
tbattery2
Low-battery detected
212
39
43
48
s
tchamber
No degraded chamber detected
218
41.3
45.9
50.5
min
tchamber2
Degraded chamber detected
212
39
43
48
s
–
No
LED
Pulses
–
–
tled0
No local or remote smoke, BLINK = VSS
–
tled1
No local or remote smoke, BLINK = VDD
212
39
43
48
s
tled3
Local smoke
48
0.45
0.50
0.55
s
tled4
Remote smoke only
–
–
No
LED
Pulses
–
–
tled6
Pushbutton test, induced alarm
48
0.45
0.50
0.55
s
tled7
Timer mode, no alarm
210
9.67
10.75
11.83
s
1
9.5
10.5
11.5
ms
3 pulses, degraded chamber
26
0.60
0.67
0.74
s
tst1
No local or remote smoke
210
9.6
10.75
11.9
s
tst2
After 1 of 3 valid samples
192
1.8
2.0
2.2
s
tst3
After 2 of 3 valid samples and during local alarm
96
0.8
1.0
1.1
s
tst4
Remote smoke only
768
7.2
8.0
8.9
s
tst5
Chamber test, no local alarm
218
41.3
45.9
50.5
min
tst6
Pushbutton test, induced alarm
tw(led)
tsp(led)
IRED Pulse Period
Min.
tosc
LED Pulse Spacing
STROBE Pulse Width
OSC
Count
tsmoke
LED Pulse Width
STROBE Pulse Period
Test Conditions
24
225
252
278
ms
tw(st)
1
9.5
10.5
11.5
ms
tired1
No local or remote smoke
210
9.6
10.75
11.9
s
tired2
After 1 of 3 valid samples
192
1.8
2.0
2.2
s
tired3
After 2 of 3 valid samples and during local alarm
96
0.8
1.0
1.1
s
tired4
Remote smoke only
768
7.2
8.0
8.9
s
tired5
Chamber test, no local alarm
218
41.3
45.9
50.5
min
tired6
Pushbutton test, induced alarm
24
225
252
278
ms
IRED Pulse Width
tw(ired)
0.01
94
105
116
μs
I/O to Active Delay
td(io)
Local alarm
–
–
0
–
s
I/O Charge Dump Duration
tdump
End of local alarm or test
96
0.9
1.0
1.1
s
Rising Edge on I/O to Alarm
tr(io)
No local alarm
9 to 13
9×
tosc
94.5 –
137
13 ×
tosc
ms
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
A5303
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
AC ELECTRICAL CHARACTERISTICS (continued)1 Valid at TA = 25°C, VDD = 2.3 to 5.5 V, configured as in Typical Application
Diagram (unless otherwise noted)
Characteristics
SOUTx Output Warning Period
Symbol
Test Conditions
OSC
Count
Min.
Typ.2
Max.
Unit
tsoutx
Low supply or degraded chamber
212
38.9
43
47.1
s
tw(soutx)
Low supply or degraded chamber
1
9.5
10.5
11.5
ms
Horn Warning Pulse Period
thorn
Low battery or degraded chamber
212
38.9
43
47.1
s
Horn Warning Pulse Width
tw(horn)
Low battery or degraded chamber
1
9.5
10.5
11.5
ms
Horn Warning Pulse Spacing
tsp(horn)
3 chirps, degraded chamber
26
0.60
0.67
0.74
s
Horn On-Time
ton(horn)
Local, remote, or test alarm
48
450
500
550
ms
toff1(horn)
Local, remote, or test alarm (see Timing
Diagrams section)
48
450
500
550
ms
toff2(horn)
Local, remote, or test alarm (see Timing
Diagrams section)
144
1350
1500
1650
ms
57344
9.0
10.0
11.0
min
×
tosc
21.5 –
32.3
3072 ×
tosc
s
SOUTx Output Warning Pulse Width
Horn Off-Time
Timer Mode Duration
Failed Push-Test Indication on SOUTx
1Limits
ttimer
tFAIL
After TEST input goes low
211
to
3072
211
over the operating temperature range are based on characterization data. Characteristics are production tested at 25°C only.
values are at 25°C and are given for circuit design information only.
2Typical
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
A5303
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
Pin and Circuit Description
(In Typical Application)
C1 Pin
A capacitor connected to this pin determines the gain of the
photoamplifier, Ae , during the push-to-test mode and during the
chamber monitor test. A typical capacitor value for this highgain (supervisory) mode is 0.047 μF, but it should be selected
based on the photochamber background reflections reaching the
detector and the required level of sensitivity. Ae = 1 + (C1 / 12),
where C1 is in pF. Ae should not exceed 10,000 and thus C1
should not exceed 0.1 μF. Coupling of other signals to the C1,
C2, and DETECT inputs must be minimized.
C2 Pin
A capacitor connected to this pin determines the gain of the
photoamplifier, Ae, during standby. A typical capacitor value for
this low-gain mode is 4700 pF, but it should be selected based
on a specific photochamber and the desired level of sensitivity to smoke. Ae = 1 + (C2 / 12), where C2 is in pF. Ae should not
exceed 10,000 and thus C2 should not exceed 0.1 μF. This gain
increases by a nominal 45% after a local alarm is detected (three
consecutive detections). A resistor must be installed in series
with the C2 capacitor.
DETECT Pin
This is the input to the photoamplifier and is connected to the
cathode of the photodiode. The photodiode is operated at zero
bias and should have low dark leakage current and low capacitance. A shunt resistor must be installed in parallel with the
photodiode.
STROBE Pin
This output provides a strobed, regulated voltage of VDD – 2 V.
The minus side of all internal and external photoamplifier circuitry is referenced to this pin.
VDD Pin
This pin is connected to the positive supply potential,
typically 3 V.
LVSET Pin
This pin allows the user to externally adjust the low-battery
alarm threshold. To increase the threshold, a resistor can be connected between LVSET and VDD. To decrease the threshold, a
resistor can be connected between LVSET and VSS.
IRED Pin
This output provides a pulsed drive current for the external IR
emitter. To minimize noise impact, the IRED is not active when
the visible LED output is active.
ISET Pin
This pin allows the user to externally set the IRED current by
connecting a resistor between it and VSS. The IRED current
controls the amount of light generated by the IR LED in the
chamber. The IRED current, in mA, can be approximated using
the following equation:
IIRED (mA) = 300 / RISET(1)
The chosen resistor should set a maximum of 300 mA (typically
a minimum of 1Ω).
I/O Pin
A connection at this pin allows multiple smoke detectors to be
interconnected. If any single unit detects smoke, its I/O pin is
driven high, and all connected units will sound their associated
alarm indicators. As an input, this pin is sampled every 4 clock
cycles (nominally 43 ms) during standby, and two consecutive
samples and one additional clock with I/O high are required
before signaling an alarm. If the I/O line goes low at all during
the 96.8 ms, the remote alarm is not enabled, providing significant immunity to I/O noise and other pulses on the I/O line
which are shorter than 9 clock cycles. The LED is suppressed
when an alarm is signaled from an interconnected unit, and
any local-alarm condition causes this pin to be ignored as an
input. An internal NMOS device acts as a charge dump to aid
in applications involving a large (distributed) capacitance, and
is activated at the end of a local or test alarm. This pin has an
on-chip pull-down device and must be left unconnected if not
used. In the application, there should be a series current-limiting
resistor to other smoke alarms.
SOUT0, SOUT1, SOUT2 Pins
These pins provide push-pull CMOS logic outputs to control an
external sound IC. The outputs indicate the state of the device as
follows:
Condition
Standby
Local Alarm
Remote Alarm
Push-Test Passed
Push-Test Failed
Low-Battery
Degraded Chamber
SOUT2
L
L
L
L
H
H
H
SOUT1
L
L
H
H
L
L
H
SOUT0
L
H
L
H
L
H
L
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
6
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
A5303
HORN Pin
The HORN pin is a logic output provided to enable an optional,
external boost converter that can drive a piezoelectric (piezo)
horn. Using a boost converter to drive a piezo horn allows alarms
to generate high SPL levels from low supply voltages. HORN will
be driven high to enable the boost converter. The output of the
boost converter will be connected to the piezo horn such that the
horn will sound when the converter is enabled. If a boost converter and horn are not used, this pin should be left open.
BLINK Pin
This logic input determines the LED operation while the device is
in standby. If BLINK is connected to VDD the device will blink
once every approximately 43 s in standby. If BLINK is connected
to VSS the device will not blink in standby. If a low-battery or
degraded-chamber condition exists while the device is in standby,
the LED will blink as described in the Alarm Indications section,
regardless of the state of the BLINK pin. The BLINK pin has no
effect when the device is in local, remote, or test alarm.
LED Pin
This open-drain NMOS output is used to directly drive a visible
LED. The LED indicates detector status as follows (with component values as in the typical application, all times nominal):
nominally 105 μs. The internal clock high time can be calculated
by:
Thigh = 0.693 × RTRES × COSCCAP(3)
VSS Pin
This pin is connected to the negative supply potential (usually
ground).
HUSH Pin
This input pin serves two purposes in standby mode. It serves to
enable/disable entering the internal 10-minute (nominal) “hush”
timer mode, and also as the reference for the smoke comparator
during timer mode. Timer mode allows the user to temporarily
hush alarms caused by nuisance smoke or steam (such as from
cooking).
When the voltage on this pin is greater than approximately
50 mV, entering timer mode is enabled, and a high-to-low transition on the TEST pin resets and starts timer mode. If use of timer
mode is not desired this pin must be connected to VSS, and timer
mode is disabled.
OSC CAP (Oscillator Capacitor) Pin
During timer mode the smoke comparator reference is established
externally by a resistive divider (R1 and R2) between VDD and
STROBE. Also, during timer mode the photoamplifier gain, Ae,
is internally reduced to about 55% that during the normal-gain
mode. Thus, Ae = 1 + (C2 / 22), where C2 is in pF. These two
conditions allow the detector to operate with reduced sensitivity
during timer mode. If the level of smoke increases such that the
temporary alarm threshold is reached, a local alarm will sound. If
the HUSH pin is connected directly to STROBE without using a
resistor divider, then a local alarm will never occur during timer
mode, regardless of the smoke level. When not in timer mode,
the smoke comparator reference is set internally to approximately
VDD – 1.6 V.
A capacitor between this pin and VDD, along with a parallel
resistor, forms part of a two-terminal oscillator and sets the internal clock low time. With component values shown, this nominal
time is 10.4 ms and essentially the oscillator period, which is also
the STROBE pulse width. The internal clock low time can be
calculated by:
The resistor dividers formed by the adjustable photoamp-divider
and the HUSH divider (R1 + R2, if timer mode is used) should
be chosen so that the load on STROBE does not exceed 500 μA.
Thus, the photoamp-divider (8 kΩ in the typical application) in
parallel with the HUSH divider (R1 + R2) shall be no
less than 4 kΩ.
Condition
Pulse Occurrence
Standby, BLINK = VDD
Every 43.0 s
Standby, BLINK = VSS
No LED pulses
Local Smoke
Every 0.5 s
Remote Alarm
No pulses
Test Mode
Every 0.5 s
Timer (Hush) Mode
Every 10.8 s
TEST Pin
This pin has an internal pulldown device and is used to manually
invoke push-to-test mode and timer mode. Push-to-test mode is
TRES (Timing Resistor) Pin
A resistor between this pin and OSC CAP is part of the two-termi- initiated by a voltage greater than approximately VDD – 0.5 V
on this pin (usually the closure of a normally open push-button
nal oscillator and sets the internal clock high time, which is also
the IRED pulse width. With component values shown, this time is switch to VDD). After one oscillator cycle, the amplifier gain is
Tlow = 0.693 × ROSCCAP × COSCCAP(2)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
7
A5303
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
increased by internal selection of C1 so that background reflections in the smoke chamber can be used to simulate a smoke condition, and IRED pulses every 252 ms (nominal). After the third
IRED pulse (three consecutive simulated smoke conditions), the
successful test signals a continuous passing-test-alarm condition
to the sound IC, outputs the temporal pattern to the piezo horn,
and activates the I/O pin. When the pushbutton is released, the
input returns to VSS due to the internal pulldown. After one oscillator cycle, the amplifier gain returns to normal, and after three
additional IRED pulses (less than one second), the device exits
this mode and returns to standby. This high-to-low transition on
TEST also resets and starts the 10-minute (nominal) “hush” timer
mode, if the mode is enabled via the HUSH pin. The high-to-low
transition also resets the latching alarm indicator, if it is latched.
If the chamber malfunctions or is too dirty, the push-test will fail
to simulate a smoke condition, and after three failed STROBE
pulses the device signals a continuous failing-test-alarm condition on the SOUTx pins. The piezo driver and the I/O pins are not
enabled.
Diagnostic Test/Calibration mode is available to facilitate calibration and test of the IC and the assembled detector. It is initiated
by pulling TEST below VSS by continuously drawing 200 μA
from the pin for at least one clock cycle on OSC CAP. The current should not exceed 500 μA and under these conditions,
TEST pin voltage will clamp at approximately 250 mV below
VSS. One option is to connect TEST to a –5 V supply through a
15 kΩ resistor. In this mode, certain device pins are reconfigured
as described in table 1. The IRED pulse rate is increased to one
pulse every OSC CAP cycle and the STROBE pin is always
active. To exit this mode, the TEST pin should be floated, or
returned to VSS, for at least one OSC CAP cycle.
Latching Alarm Indicator
When multiple smoke detectors are networked through the I/O
line, the latching alarm indicator allows the user to identify which
detector(s) initiated an alarm. When a local alarm condition
occurs, the initiating detector(s) will latch the event in memory.
After the alarm condition has expired (the device stops signaling
the alarm condition to the sound IC) the initiating detector(s) will
output an additional 10 ms LED pulse every 43 seconds. If the
BLINK pin is connected to VDD, the additional pulse will occur
0.67 seconds after the normal standby pulse. The user can clear
the latched alarm condition by pressing and releasing the push-totest button. If the user does not press the push-to-test button, the
latched alarm condition will cease after 24 hours to preserve battery life, and to prevent masking future latched alarm indications.
Alarm Indications
Alarm conditions include: local smoke detection, a remote alarm,
low battery, and degraded chamber sensitivity. These are indicated by a combination of SOUTx output, piezo horn, and LED
signals, which continue until the alarm condition is resolved.
A local alarm always overrides a remote alarm and a push-test.
Remote alarm always overrides a push-test. A local alarm, remote
alarm, or a push-test will inhibit warning signals for low battery
or degraded chamber.
During a local or a remote alarm condition, the device continuously signals an alarm condition on the SOUTx pins that indicates the type of the alarm. The piezo horn output is a continuous
modulated tone (temporal horn pattern), nominally: 0.5 s on, 0.5 s
off, 0.5 s on, 0.5 s off, 0.5 s on, and 1.5 s off. The visible LED
also distinguishes a local alarm from a remote alarm. During a
Table 1. Alternate Pin Configuration During Diagnostic
Test/Calibration Mode
Pin Name
Alternate Configuration
I/O
Disabled as an output. A logic high on this pin places the
photoamplifier output on the BLINK pin. The amplifier
output appears as pulses.
HUSH
If the I/O pin is high, this pin controls the amplifier gain
capacitor. If this pin is low, normal gain is selected. If this
pin is high, supervisory gain is selected.
NOTE: If I/O is low, clocking this pin will cause the
device to exit diagnostic/calibration mode and enter an
Allegro-defined test mode.
BLINK
If the I/O pin is high, this pin is reconfigured as the
photoamplifier output.
SOUT0
If the I/O pin is high and the HUSH pin is low (normal
gain), taking this pin to a high logic level increases the
amplifier gain by ≈45% (hysteresis).
SOUT2
This pin is reconfigured as the smoke integrator output.
Three consecutive smoke detections will cause this pin
to go high and three consecutive no-smoke detections
cause this pin to go low.
LED
This pin becomes a low-battery indicator. The opendrain NMOS output is normally off. If VDD falls below the
low-battery threshold, the output turns on.
OSC CAP
This pin may be driven by an external clock source.
Driving this pin low and high drives the internal clock low
and high. The external RC network may remain intact.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
8
A5303
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
local alarm, the LED blinks every 0.5 s (nominally), but during a
remote alarm, the LED is disabled and does not blink.
cleared or cleaned, and the test period then reverts to (nominally)
45.9 min.
The degraded-chamber test occurs periodically (nominally every
45.9 min). During this test, the gain of the photoamplifier is
switched to the high (supervisory) level, set by C1. The device
expects that the photodiode will receive enough background
reflections in the chamber to cause an alarm condition. If a faulty,
dirty, or obstructed chamber prevents this during a test, the test
period decreases to 43 s. After two consecutive failed tests, the
device signals a degraded chamber condition to the sound IC.
It also chirps the horn and pulses the LED three times every
43 seconds. The condition is resolved when the chamber is either
The low-battery test also occurs periodically (also nominally
every 45.9 min, but at a different time than the degraded-chamber
test). During this test a resistive divider off VDD is compared to
an internal band-gap reference. If VDD is below the threshold, the
device signals a low battery condition to the sound IC and the
test period decreases to 43 s. It also chirps the horn and pulses the
LED once every 43 seconds. The condition is resolved when the
battery is replaced and the test period then reverts to (nominally)
45.9 min.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
9
A5303
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
Timing Diagrams
(Not to Scale)
Standby Mode
OSC CAP
tw(ired)
Test event
Internal clock
tosc
tbattery, tled0, tst5, tired5
tsmoke, tst1, tired1
Photo sample
Low-battery test
Chamber test
tw(st)
tchamber, tst5, tired5
STROBE
IRED
tled1
tw(led)
LED, BLINK = VDD
LED, BLINK = VSS
(LED OFF)
Low Battery Condition
VDD
(Low battery)
tbattery
tbattery2
tbattery2
tbattery
Low-battery test
tsoutx
SOUTx
tw(soutx)
SOUT(2:0) = (HLH)
thorn
tw(horn)
HORN
tled1
tw(horn)
LED
these two pulses will not exist if BLINK = VSS
Degraded Chamber Condition
Chamber
sensitivity
Chamber test
(Degraded chamber)
tchamber
tchamber2
tchamber2
tsoutx
SOUTx
tchamber
tw(soutx)
SOUT(2:0) = (HHL)
thorn
tw(horn)
HORN
tsp(led)
tsp(horn)
LED
tw(led)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
10
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
A5303
Local Smoke Detection Condition
Chamber
(smoke present)
1st strobe with smoke
3rd strobe with smoke
3rd strobe without smoke
IRED
tst2,ired2
tw(st)
tst3,ired3
STROBE
LED
tw(led)
tled3
tst3,ired3
BLINK = VSS or VDD
SOUTx
SOUT(2:0) = (LLH)
ton(horn)
toff2(horn)
toff1(horn)
HORN
tdump
I/O
(OUTPUT)
I/O charge dump
Remote Alarm Condition
LED
BLINK = VSS or VDD
(LED OFF)
tw(st)
tst4,ired4
STROBE
SOUTx
SOUT(2:0) = (LHL)
ton(horn)
toff2(horn)
toff1(horn)
HORN
tr(io)
I/O
(INPUT)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
11
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
A5303
Test Alarm Mode (passing)
LED
BLINK = VSS or VDD
tw(led)
tled6
STROBE
tw(st)
tst6,ired6
TEST
SOUTx
SOUT(2:0) = (LHH)
ton(horn)
toff2(horn)
toff1(horn)
HORN
tdump
I/O
(OUTPUT)
I/O charge dump
Test Alarm Mode (failing)
LED
BLINK = VSS or VDD
tw(led)
tw(st)
STROBE
TEST
SOUTx
SOUT(2:0) = (HLL)
tFAIL
HORN
I/O
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
12
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
A5303
Package ES, 20-Contact QFN
with Exposed Thermal Pad
0.30
4.00 ±0.10
1
2
0.50
20
20
0.95
A
1
2
4.00 ±0.10
2.45
4.10
2.45
4.10
21X
D
SEATING
PLANE
0.08 C
+0.05
0.25 –0.07
0.75 ±0.05
0.50 BSC
C
C
PCB Layout Reference View
For Reference Only, not for tooling use (reference DWG-2864)
Dimensions in millimeters
Exact case and lead configuration at supplier discretion within limits shown
A Terminal #1 mark area
B Exposed thermal pad (reference only, terminal #1
identifier appearance at supplier discretion)
0.40 ±0.10
B
2
1
+0.10
2.45 –0.15
C Reference land pattern layout (reference IPC7351
QFN50P400X400X80-21BM)
All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary
to meet application process requirements and PCB layout tolerances; when
mounting on a multilayer PCB, thermal vias at the exposed thermal pad land
can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5)
D Coplanarity includes exposed thermal pad and terminals
20
+0.10
2.45 –0.15
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
13
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
A5303
Package LE, 20-Pin TSSOP
0.45
6.50±0.10
8º
0º
20
20
0.20
0.09
4.40±0.10
0.65
1.70
6.10
6.40±0.20
0.60 ±0.15
A
1
1.00 REF
2
0.25 BSC
20X
SEATING
PLANE
0.10 C
0.30
0.19
1.20 MAX
0.65 BSC
0.15
0.00
C
SEATING PLANE
GAUGE PLANE
1
2
B
PCB Layout Reference View
For Reference Only; not for tooling use (reference MO-153 AC)
Dimensions in millimeters
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
B Reference land pattern layout (reference IPC7351
SOP65P640X110-21M);
All pads a minimum of 0.20 mm from all adjacent pads; adjust as
necessary to meet application process requirements and PCB layout
tolerances; when mounting on a multilayer PCB, thermal vias at the
exposed thermal pad land can improve thermal dissipation (reference
EIA/JEDEC Standard JESD51-5)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
14
A5303
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
Revision History
Revision
Revision Date
Rev. 1
November TBD, 2012
Description of Revision
Add ES package
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 ©2001-2012, Allegro MicroSystems, Inc.
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 any devices or systems, including but not limited to life support devices or systems, in which a failure of
Allegro’s product can reasonably be expected to cause bodily harm.
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
15