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RE46C145 Datasheet - Page 7

Download or read online Microchip Technology RE46C145 CMOS Photoelectric Smoke Detector ASIC With Interconnect And Timer Mode pdf datasheet.



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2.0
PIN DESCRIPTION
The descriptions of the pins are listed in .
TABLE 2-1:
PIN FUNCTION TABLE
RE46C145
Symbol
PDIP, SOIC, SOICN
1
C1
2
C2
3
DETECT
4
STROBE
5
V
DD
6
IRED
7
IO
8
HB
9
HS
10
FEED
11
LED
12
COSC
13
ROSC
14
V
SS
15
VSEN
16
TEST
2.1
High/Normal Gain Capacitor Pins
(C1, C2)
The capacitor connected to C1 pin sets the photo
amplifier gain (high) for the push-to-test and chamber
sensitivity test. The size of this capacitor will depend on
the chamber background reflections. A = 1+(C1/10),
where C1 is expressed in pF. The gain should be
<10000.
The capacitor connected to C2 pin sets the photo
amplifier gain (normal) during standby. The value of this
capacitor will depend on the smoke sensitivity required.
A = 1+(C2/10), where C2 is expressed in pF.
2.2
Photo Diode Input (DETECT)
This input is normally connected to the cathode of an
external photo diode operated at zero bias.
2.3
Strobed Detection
Negative Supply (STROBE)
Regulated output voltage of V
-5 which is active
DD
during a test for smoke. This output is the negative side
of the photo amplifier reference circuitry.
 2009-2012 Microchip Technology Inc.
Function
High Gain Capacitor Pin
Normal Gain Capacitor Pin
Photo Diode Input
Strobed Detection Negative Supply
Positive Power Supply
Infrared Emitting Diode Pin
Interconnect Pin
Horn Brass, Inverted Output
Horn Silver Output
Horn Feedback Pin
LED Driver Pin
Oscillator Capacitor Input
Oscillator Resistor Drive Low
Negative Power Supply
HushTimer Sensitivity Pin
Test Pin
2.4
Positive Power Supply (V
The V
pin is the device’s positive power supply input.
DD
2.5
Infrared Emitting Diode Pin (IRED)
Provides a regulated pulsed output voltage pre-driver
for the infrared emitter. This output usually drives the
base of an NPN transistor.
2.6
Interconnect Pin (IO)
This bidirectional pin provides the capability to
interconnect many detectors in a single system. This
pin has an internal pull-down device.
2.7
Horn Brass, Inverted Output (HB)
HB pin is connected to the metal electrode of a
piezoelectric transducer.
2.8
Horn Silver Output Pin (HS)
HS pin is a complementary output to HB and connects
to the ceramic electrode of the piezoelectric transducer.
RE46C145
)
DD
DS22181C-page 7

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