Datenblatt-pdf.com


A5303 Schematic ( PDF Datasheet ) - Allegro

Teilenummer A5303
Beschreibung Photoelectric Smoke Detector
Hersteller Allegro
Logo Allegro Logo 




Gesamt 15 Seiten
A5303 Datasheet, Funktion
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.
20-contact QFN
4 mm × 4 mm × 0.75 mm
(ES package)
TheA5303 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.
Typical Application Diagram
VDD
R1 3 k
5 k
R2
56 nF
5.6 nF 560
200 k
C1
C2
DETECT
1 k
VDD
100 µF
Smoke
Chamber
3
STROBE
IRED
ISET
Connect HUSH to
VSS to disable
timer mode
HUSH
VSS
To / from
other units
220
Gain
Select
VDD -
1.6 V
VDD 1.2 V
Low Batt
Control
Logic
VDD
LVSET
Low Batt
Sample
TEST
BLINK
SOUT0
SOUT1
SOUT2
HORN
LED
VDD 3 V
10 µF
A
Push-to-test
B
Voice IC outputs
Output to optional
boost converter to
drive a piezo horn
Red LED
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
OSC
Timing
OSCCAP
TRES
100 kΩ
1500 pf
10 ΜΩ
5303-DS, Rev. 1






A5303 Datasheet, Funktion
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 high-
gain (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 sensitiv-
ity 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 capaci-
tance. 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 cir-
cuitry 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 con-
nected 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 sig-
nificant 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

6 Page









A5303 pdf, datenblatt
A5303
Photoelectric Smoke Detector
with Interconnect, Timer, and Latching Alarm Indicator
Test Alarm Mode (passing)
LED
BLINK = VSS or VDD
STROBE
TEST
tw(led)
tw(st)
SOUTx
HORN
ton(horn)
tled6
tst6,ired6
SOUT(2:0) = (LHH)
toff2(horn)
I/O (OUTPUT)
Test Alarm Mode (failing)
LED
BLINK = VSS or VDD
STROBE
tw(led)
TEST
SOUTx
HORN
I/O
tw(st)
SOUT(2:0) = (HLL)
toff1(horn)
tdump
I/O charge dump
tFAIL
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
12

12 Page





SeitenGesamt 15 Seiten
PDF Download[ A5303 Schematic.PDF ]

Link teilen




Besondere Datenblatt

TeilenummerBeschreibungHersteller
A5303Photoelectric Smoke DetectorAllegro
Allegro

TeilenummerBeschreibungHersteller
CD40175BC

Hex D-Type Flip-Flop / Quad D-Type Flip-Flop.

Fairchild Semiconductor
Fairchild Semiconductor
KTD1146

EPITAXIAL PLANAR NPN TRANSISTOR.

KEC
KEC


www.Datenblatt-PDF.com       |      2020       |      Kontakt     |      Suche