A5358(1996) 查看數據表（PDF） - Allegro MicroSystems
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A5358 Datasheet PDF : 12 Pages
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5358
PHOTOELECTRIC SMOKE DETECTOR
with INTERCONNECT and TIMER
PIN AND CIRCUIT DESCRIPTION
(In Typical Application)
PIN 1 (C1)
A capacitor connected to this pin determines the gain
of the photo amplifier during the push-to-test mode and
during the chamber monitor test. A typical value for this
high-gain mode is 0.047 µF but should be selected
based on the photo chamber background reflections
reaching the detector and the desired level of sensitivity.
Ae ≈ 1+(C1/10) where C1 is in pF. Ae should not
exceed 10 000.
PIN 2 (C2)
A capacitor connected to this pin determines the gain
of the photo amplifier during standby. A typical value for
this low-gain mode is 4700 pF but should be selected
based on a specific photo chamber and the desired level
of sensitivity to smoke. Ae ≈ 1+(C2/10) where C2 is in pF.
Ae should not exceed 10 000. This gain increases by a
nominal 10% after a local alarm is detected (three con-
secutive detections). Coupling of other signals to C2
(C1 and the DETECT inputs also) must be minimized.
A resistor must be installed in series with C2.
PIN 3 (DETECT)
This is the input to the photo amplifier and is con-
nected to the cathode of the photo diode. The photo
diode is operated at zero bias and should have low dark-
leakage current and low capacitance.
PIN 4 (STROBE)
This output provides a strobed, regulated voltage of
VDD – 5 V. The minus side of all internal and external
photo amplifier circuitry is referenced to this pin.
PIN 5 (VDD)
This pin is connected to the most-positive supply
potential and can range from 6 V to 12 V with respect
to VSS.
PIN 6 (IRED)
This output provides a pulsed base current for the
external npn transistor, which drives the IR emitter. Its
beta should be greater than 100. The IRED output is not
active, to minimize noise impact, when the horn and
visible LED outputs are active.
PIN 7 (I/O)
A connection at this pin allows multiple smoke detec-
tors to be interconnected. If a local smoke condition
occurs, this pin is driven high. As an input, this pin is
sampled nominally every 1.35 seconds during standby.
Any local-alarm condition causes this pin to be ignored as
an input.
This pin has an on-chip pull-down resistor and must
be left unconnected if not used. In application, there is a
series current-limiting resistor to other smoke alarms.
PIN 8 (HORN1)
PIN 9 (HORN2)
PIN 10 (FEEDBACK)
These three pins are used in conjunction with external
passive components and a self-resonating piezoelectric
transducer. HORN1 is connected to the piezo metal
support electrode; the complementary output, HORN2, is
connected to the ceramic electrode and the FEEDBACK
input to the feedback electrode.
A continuous modulated tone indicates either a local
or remote alarm condition. A short (10 ms) chirp indicates
a low-battery condition or degraded chamber sensitivity.
The low-battery chirp occurs almost simultaneous with the
visible LED flash. If the FEEDBACK pin is not used, it
must be connected to VDD or VSS.
Continued...
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
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