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MC14568 Datasheet(PDF) 4 Page - Freescale Semiconductor, Inc

Part No. MC14568
Description  Low-Power CMOS Ionization Smoke Detector with Interconnect and Timer
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Maker  FREESCALE [Freescale Semiconductor, Inc]
Homepage  http://www.freescale.com
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MC14568 Datasheet(HTML) 4 Page - Freescale Semiconductor, Inc

 
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Sensors
4
Freescale Semiconductor
MC14568
PIN DESCRIPTIONS
TIMER START (PIN 1)
An internal timer is provided that can be used in various
configurations to allow for a period of reduced smoke
detector sensitivity (“hush”). When a high-to-low transition
occurs at pin 1, the internal timer is reset, the timer mode
enabled, and the circuit reset to a no alarm condition.
I/O (PIN 2)
Pin 2 is an input/output pin designed to be connected to
other smoke units for remote smoke sensing. In a local
smoke condition, this pin is driven high by the unit sensing
smoke. All other units in the network will then go into remote
smoke mode.
LOW-V SET (PIN 3)
Pin 3 is the low voltage set pin. This pin has an internal
fixed bias to monitor the battery. Using an external resistor
from pin 3 to either VDD or VSS allows the user to change
this bias to some fraction of VDD.
TIMER OUTPUT (PIN 4)
This pin is an open drain output that can be used in various
timer configurations to alter the IC’s sensitivity. A high to low
transition on pin 1 causes this output to pulse for 231 internal
clock cycles.
LED (PIN 5)
This pin is the LED cathode connection pin and is driven
low when the LED pulses.
VDD (PIN 6)
This is the positive power supply for the entire IC.
TIMING RESISTOR (PIN 7)
This pin, when tied through a resistor to VDD, works along
with pin 12 to set the bias current that controls the oscillation
frequency.
FEEDBACK (PIN 8)
This is the feedback pin used for driving the piezo electric
element.
VSS (PIN 9)
This is the negative power supply pin for the entire IC
(usually ground).
HORN 1 (PIN 10)
This is one of two pins that drive the horn element (i.e.,
brass and silver).
HORN 2 (PIN 11)
This is one of two pins that drive the horn element (i.e.,
brass and silver).
OSCILLATOR CAP (PIN 12)
This pin, when tied to a low leakage capacitor to VSS,
works with pin 7 to set the internal oscillation frequency.
SENSITIVITY SET (PIN 13)
This pin is set internally to provide the reference sensitivity
for the detect pin (pin 15).
An external resistor from pin 13 to either VDD or VSS can
adjust the sensitivity.
GUARD 1/LOW Z (PIN 14)
This pin provides a low impedance guard for the detect pin
(pin 15) to reduce leakage currents.
DETECT INPUT PIN (PIN 15)
This pin functions as a low leakage smoke detect pin when
used in conjunction with an Ionization type element.
GUARD 2/HIGH Z (PIN 16)
This pin provides a high impedance guard for the detect
pin (pin 15) to reduce leakage currents.
II/O
I/O Current(1)
VI/O = VDD - 2.0 V
VI/O = VDD - 2.0 V
VI/O = 1.0 V
No Alarm
Alarm
Charge Dump
225
-75
5.0
60
µA
mA
mA
I/O Charge Dump Duration
After Local Alarm or Test
2
1.33
1.66
1.99
s
I/O Delay
Alarm Out
2
3.0
s
VI/O
I/O VIH, VIL
VIH, VDD = 9.0 V
VIL, VDD = 9.0 V
23.2
1.5
V
IDD
Supply Current
VDD = 9.0 V
VDD = 12 V
No Alarm, No Loads
No Alarm, No Loads
6—
5.0
9.0
12
µA
1. This specification also shows VOH of VDD - 2.0 V and VOL of 1.0 V at respective currents.
2. Negative current is defined as coming out of (sourcing) the specified device pin.
3. Alarm (Smoke) Condition is defined as V15 < V13; No Alarm (No Smoke) Condition as V15 > V13.
4 No Loads means the IC in standby mode with a 0.1
µF capacitor on pin 12 to VSS and an 8.2 MΩ resistor on pin 7 to VDD with Pin 2 tied
low (LED and Horn are off).
Table 2. Electrical Characteristics (continued)
Characteristics noted under conditions TA = +25°C, VDD = 9.0 V, VSS = 0 V, C12 = 0.1 µF (Oscillator Pin) R7 = 8.2 mΩf/fn (timing
resistor pin) unless otherwise noted.
Symbol
Characteristic
Test Condition
Test
Pin
Min
Typ
Max
Unit


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