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MC146010EG View Datasheet(PDF) - Freescale Semiconductor

Part Name
Description
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MC146010EG
Freescale
Freescale Semiconductor Freescale
MC146010EG Datasheet PDF : 18 Pages
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PIN DESCRIPTIONS
C1 (PIN 1)
A capacitor connected to this pin as shown in Figure 5
determines the gain of the on-chip photo amplifier during
pushbutton test and chamber sensitivity test (high gain). The
capacitor value is chosen such that the alarm tripped from
background reflections in the chamber during pushbutton
test.
AV = 1+(C1/10) where C1 is in pF. CAUTION: The value of
the closed-loop gain should not exceed 10,000.
Resistor R15 should be installed in series with C1 for lower
gains. R15 =[1/(12C1]-680 where R15 is in ohms and C1 is
in farads.
C2 (PIN 2)
A capacitor connected to this pin as shown in Figure 5
determines the gain of the on-chip photo amplifier during
pushbutton test and chamber sensitivity tests.
AV = 1+(C2/10) where C1 is in pF. This gain increases
about 10% during IRED pulse, after two consecutive local
smoke detections.
For proper compensation, resistor R14 must be installed in
series with C2. R14 =[1/(12C2]-680 where R14 is in ohms
and C1 is in farads.
DETECT (PIN 3)
This input to the high-gain pulse amplifier is tied to the
cathode of an external photodiode. The photodiode should
have low capacitance and low dark leakage current. The
diode must be shunted by a load resistor and is operated at
zero bias.
The Detect input must be ac/dc decoupled from all other
signals, VDD and VSS. Lead length and/or foil traces to this
pin must be minimized also. See Figure 3.
The device has a sampling speed-up mode after the first
smoke sample is detected. The speed-up frequency is one
smoke sample about every 2 seconds for the duration of a
smoke condition. It will take no-smoke samples to return to a
standby mode. Once out of a smoke condition, the IC will
continue to sample for smoke about every 8 seconds.
STROBE (PIN 4)
This output provides the strobed, regulated voltage
referenced to VDD. The temperature coefficient of this voltage
is ±0.2%/°C maximum from -10 to 60°C. The supply-voltage
coefficient (line regulation) is ±0.2%/V maximum from 6.0 to
12 V. Strobe is tied to external resistor string R8, R9 and R10.
VDD (PIN 5)
This pin is connected to the positive supply potential and
may range from +6.0 to +12 V with respect to VSS.
CAUTION: In battery-powered applications, reverse-
polarity protection must be provided exter-
nally.
IRED (PIN 6)
This output provides pulsed base current for external NPN
transistor Q1 used as the infrared emitter driver. Q1 must
have a β ≥ 100. At 10 mA, the temperature coefficient of the
output voltage is typically +0.5%/°C from -10 to 60°C. The
supply-voltage coefficient (line regulation) is ±0.2%/V
maximum from 6.0 to 12 V. The IRED pulse width (active-
high) is determined by external components R1 and C3. With
a 100 k/1500 pF combination, the nominal width is 105 µs.
To minimize noise impact, IRED is active near the end of
strobe pulses for smoke tests, chamber sensitivity test, and
pushbutton test. For the above mentioned width, IRED will be
active for the last 105 µs of strobe pulse.
I/O (PIN 7)
This pin can be used to connect up to 40 units together in
a wired-OR configuration for common signaling. VSS is used
as the return. An on-chip current sink minimizes noise pickup
during non-smoke conditions and eliminates the need for an
external pull-down resistor to complete the wired-OR.
Remote units at lower supply voltages do not draw excessive
current from a sending unit at higher supply voltage.
I/O can also be used to activate escape lights, auxiliary
alarms, remote alarms and/or auto-dialers.
As an input, this pin feeds a positive-edge-triggered flip-
flop whose output is sampled nominally every 1 second
during standby (using typical component values). Once the
first I/O remote smoke sample is detected, a second sample
approximately 10 ms later will happen to confirm a remote
smoke condition. If both samples are found to be high, the
unit will start sounding an alarm.
I/O is disabled by the on-chip power-on reset to eliminate
nuisance signaling during battery changes or system power-
up.
If unused, I/O must be left unconnected.
BRASS (PIN 8)
This half of the push-pull driver output is connected to the
metal support electrode of the piezoelectric audio transducer
and to the horn-starting resistor. A continuous modulated
tone from the transducer is a smoke alarm indicating either
local or remote smoke. A short beep or chirp is a trouble
alarm indicating a low supply or degraded chamber
sensitivity. A series of short beeps or chirps during a
pushbutton test indicate a previous alarm for detected smoke
(Alarm memory feature).
SILVER (PIN 9)
This half of the push-pull driver output is connected to the
ceramic electrode of a piezoelectric transducer and to the
horn-starting capacitor.
FEEDBACK (PIN 10)
This input is connected to both the feedback electrode of
a self-resonating piezoelectric transducer and the horn-
starting resistor and capacitor through current limiting resistor
R4. If unused, the pin must be tied to VSS or VDD.
LED (PIN11)
This active-low open drain output directly drives an
external visible LED at the pulse rate indicated below. The
pulse width is equal to the OSC period.
Sensors
Freescale Semiconductor
MC146010
9
 

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