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
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.
Packages:
20-pin TSSOP
(LE package)
Not to scale
20-contact QFN
4 mm × 4 mm × 0.75 mm
(ES package)
Typical Application Diagram
To / from
other units
V
DD
56 nF
C1
R1
3 kΩ
5.6 nF
560
Ω
C2
220
Ω
V
DD
V
DD
1.2 V
VDD
LVSET
Low Batt
Low Batt
Sample
TEST
DETECT
Smoke
Chamber
V
DD
1 k
Ω
STROBE
V
DD
-
1.6 V
Control
Logic
BLINK
SOUT0
SOUT1
SOUT2
HORN
LED
3V
I/O
Gain
Select
A
Push-to-test
10 µF
Connect to allow timer (hush) mode operation
5 k
Ω
R2
200 kΩ
B
Voice IC outputs
Output to optional
boost converter to
drive a piezo horn
Red LED
A
B
A resistor connected
between this pin and
VDD or VSS adjusts
the low-battery threshold
In standby, BLINK = V
DD
causes LED to blink,
BLINK = V
SS
causes
LED not to blink
IRED
ISET
3
Ω
HUSH
Connect HUSH to
VSS to disable
timer mode
100 µF
OSC
Timing
OSCCAP
1500 pf
TRES
100
kΩ
10
ΜΩ
VSS
5303-DS, Rev. 1
A5303
Selection Guide
Part Number
A5303SESTR-T
A5303SLE-T
A5303SLETR-T
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
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
Supply Voltage Range
DC Input Voltage Range
Operating Ambient Temperature Range
Maximum Junction Temperature
Storage Temperature Range
Symbol
V
DD
V
IN
T
A
T
J
(max)
T
stg
Referenced to V
SS
Referenced to V
SS
Allegro Range S
Notes
Rating
–2.3 to 6
–0.3 to 6
–20 to 85
150
–55 to 150
Units
V
V
ºC
ºC
ºC
Thermal Characteristics
Characteristic
Package Thermal Resistance
Symbol
R
θJA
Test Conditions*
ES Package, 4-layer PCB, based on JEDEC standard
LE Package, estimated, single-layer PCB, minimal exposed copper area
Value
37
127
Units
ºC/W
ºC/W
*Additional thermal information available on Allegro website.
Pin-out Diagram
17 BLINK
18 HUSH
19 ISET
20 VDD
16 IO
Terminal List
Number
ES
14
15
LE
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
–
Name
SOUT1
SOUT0
I/O
BLINK
HUSH
ISET
VDD
IRED
STROBE
DETECT
C2
C1
LVSET
TRES
VSS
OSC CAP
TEST
HORN
LED
SOUT2
–
Function
Logic push-pull output for controlling an external sound IC
Logic push-pull output for controlling an external sound IC
Input-output to interconnected detectors
Logic input for enabling/disabling the LED blink during standby
Input for photoamplifier timer mode reference; can also disable timer mode
A resistor on this pin connected to VSS sets the IRED output current
Positive supply voltage
Terminal to drive smoke chamber IR LED
Strobed supply (V
DD
– 2 V) for photoamplifier low-side reference
Photoamplifier input
Sets photoamplifier gain in standby mode
Sets photoamplifier gain in supervisory mode
Optionally used with a resistor to adjust the low-battery threshold
Connection for resistor to set clock times/frequency
Negative supply voltage
Connection for capacitor and resistor to set clock times/frequency
Enables push-to-test mode; starts timer mode, if enabled
Logic output which optionally enables a boost converter to drive a horn
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
IRED
STROBE
DETECT
C2
C1
1
2
3
4
5
LVSET 6
OSC CAP 9
TEST 10
7
8
PAD
15
14
13
12
11
SOUT0
SOUT1
SOUT2
LED
HORN
16
17
18
19
20
1
2
3
4
TRES
ES Package
SOUT1 1
SOUT0 2
I/O 3
BLINK 4
HUSH 5
ISET 6
VDD 7
IRED 8
STROBE 9
DETECT 10
20 SOUT2
19 LED
18 HORN
17 TEST
16 OSC CAP
15 VSS
14 TRES
13 LVSET
12 C1
11 C2
VSS
5
6
7
8
9
10
11
12
13
PAD
LE Package
2
A5303
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
DC ELECTRICAL CHARACTERISTICS
1
Valid at T
A
= 25°C, V
DD
= 2.3 to 5.5 V, configured as in Typical Application Diagram
(unless otherwise noted)
Supply Voltage Range
Operating Supply Current
Characteristics
Symbol
V
DD
I
DD
Operating
During standby, STROBE off
During STROBE on, IRED off
During STROBE on, IRED on
Input Current
TEST Pulldown Current
Logic Voltage Low
Logic Voltage High
Strobe Output Voltage
Line Regulation
Strobe Temperature Coefficient
Maximum IRED Current Setting
IRED Current
IRED Temperature Coefficient
LED Drive Current
Low-Battery Warning Threshold
Low-Battery Warning Minimum
Common Mode Voltage
Smoke Comparator Reference Voltage
I/O Input Impedance
I/O Output Impedance
1
Limits
2
Typical
Test Conditions
Min.
2.3
–
–
–
–100
–
–
V
DD
×
0.7
Typ.
2
3.0
2.3
210
220
0
3.5
–
–
V
DD
V
DD
–
2.0
–60
0.01
–
100
0.40
1.2
2.5
Max.
5.5
5.0
300
300
100
–
V
DD
×
0.3
–
–
V
DD
–
1.9
–
–
300
111
–
1.8
2.6
V
DD
–
0.3
–
–
5.7
Unit
V
μA
μA
μA
nA
μA
V
V
V
V
dB
% / °C
mA
mA
% / °C
mA
V
V
I
IN
I
IN(TEST)
V
I(L)
V
I(H)
BLINK, C1, C2, DETECT, OSC CAP, TRES
(pulldown off)
V
TEST
= V
DD
= 3 V
Inactive
V
ST
Active, I
O
= 100 to 500 μA
–
V
DD
–
2.1
–
–
–
89
–
0.6
2.4
1.8
V
DD
–
1.0
–
40
–
ΔV
ST(ΔVDD)
Active, V
DD
= 2.3 to 5.5 V
α
ST
I
IRED(MAX)
I
IRED
α
IRED
I
LED
V
DD(th)
V
DD(warn)
V
IC
V
REF
Z
I/O(in)
Z
I/O(out)
V
STROBE
, V
DD
= 2.3 to 5.5 V
Current is set by selection of resistor on ISET
pin
R
ISET
= 3 Ω
I
IRED
, V
DD
= 2.3 to 5.5 V
V
LED
= 0.5 V
LVSET open
VDD voltage guaranteed to operate SOUTx pins
Photoamplifier input
Any alarm condition, except hush mode
No alarm conditions
Local or test alarm
–
V
DD
–
1.6
83
3.9
V
V
kΩ
kΩ
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.
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 CHARACTERISTICS
1
Valid at T
A
= 25°C, V
DD
= 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
Symbol
t
osc
t
smoke
t
battery
t
battery2
t
chamber
t
chamber2
t
led0
t
led1
LED Pulse Period
t
led3
t
led4
t
led6
t
led7
LED Pulse Width
LED Pulse Spacing
t
w(led)
t
sp(led)
t
st1
t
st2
STROBE Pulse Period
t
st3
t
st4
t
st5
t
st6
STROBE Pulse Width
t
w(st)
t
ired1
t
ired2
IRED Pulse Period
t
ired3
t
ired4
t
ired5
t
ired6
IRED Pulse Width
I/O to Active Delay
I/O Charge Dump Duration
Rising Edge on I/O to Alarm
t
w(ired)
t
d(io)
t
dump
t
r(io)
Local alarm
End of local alarm or test
No local alarm
No local or remote smoke
After 1 of 3 valid samples
After 2 of 3 valid samples and during local alarm
Remote smoke only
Chamber test, no local alarm
Pushbutton test, induced alarm
3 pulses, degraded chamber
No local or remote smoke
After 1 of 3 valid samples
After 2 of 3 valid samples and during local alarm
Remote smoke only
Chamber test, no local alarm
Pushbutton test, induced alarm
No low-battery detected
Low-battery detected
No degraded chamber detected
Degraded chamber detected
No local or remote smoke, BLINK = VSS
No local or remote smoke, BLINK = VDD
Local smoke
Remote smoke only
Pushbutton test, induced alarm
Timer mode, no alarm
Test Conditions
OSC
Count
1
2
10
2
18
2
12
2
18
2
12
–
2
12
48
–
48
2
10
1
2
6
2
10
192
96
768
2
18
24
1
2
10
192
96
768
2
18
24
0.01
–
96
9 to 13
Min.
9.4
9.6
41.3
39
41.3
39
–
39
0.45
–
0.45
9.67
9.5
0.60
9.6
1.8
0.8
7.2
41.3
225
9.5
9.6
1.8
0.8
7.2
41.3
225
94
–
0.9
9
×
t
osc
Typ.
2
10.5
10.75
45.9
43
45.9
43
No
LED
Pulses
43
0.50
No
LED
Pulses
0.50
10.75
10.5
0.67
10.75
2.0
1.0
8.0
45.9
252
10.5
10.75
2.0
1.0
8.0
45.9
252
105
0
1.0
94.5 –
137
Max.
11.5
11.9
50.5
48
50.5
48
–
48
0.55
–
0.55
11.83
11.5
0.74
11.9
2.2
1.1
8.9
50.5
278
11.5
11.9
2.2
1.1
8.9
50.5
278
116
–
1.1
13
×
t
osc
Unit
ms
s
min
s
min
s
–
s
s
–
s
s
ms
s
s
s
s
s
min
ms
ms
s
s
s
s
min
ms
μs
s
s
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 T
A
= 25°C, V
DD
= 2.3 to 5.5 V, configured as in Typical Application
Diagram (unless otherwise noted)
Characteristics
SOUTx Output Warning Period
SOUTx Output Warning Pulse Width
Horn Warning Pulse Period
Horn Warning Pulse Width
Horn Warning Pulse Spacing
Horn On-Time
Horn Off-Time
t
off2(horn)
Timer Mode Duration
Failed Push-Test Indication on SOUTx
1
Limits
2
Typical
Symbol
t
soutx
t
w(soutx)
t
horn
t
w(horn)
t
sp(horn)
t
on(horn)
t
off1(horn)
Test Conditions
Low supply or degraded chamber
Low supply or degraded chamber
Low battery or degraded chamber
Low battery or degraded chamber
3 chirps, degraded chamber
Local, remote, or test alarm
Local, remote, or test alarm (see Timing
Diagrams section)
Local, remote, or test alarm (see Timing
Diagrams section)
OSC
Count
2
12
1
2
12
1
2
6
48
48
144
57344
Min.
38.9
9.5
38.9
9.5
0.60
450
450
1350
9.0
2
11
×
t
osc
Typ.
2
43
10.5
43
10.5
0.67
500
500
1500
10.0
21.5 –
32.3
Max.
47.1
11.5
47.1
11.5
0.74
550
550
1650
11.0
3072
×
t
osc
Unit
s
ms
s
ms
s
ms
ms
ms
min
s
t
timer
t
FAIL
After TEST input goes low
2
11
to
3072
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.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
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