MC14568 Freescale Semiconductor, MC14568 Datasheet - Page 4

• Manufacturer Part Number: MC14568
• Description: Low-Power CMOS Ionization Smoke Detector
• Manufacturer: Freescale Semiconductor

Table 2. Electrical Characteristics (continued)
Characteristics noted under conditions T
resistor pin) unless otherwise noted.
TIMER START (PIN 1)
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)
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)
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 V
TIMER OUTPUT (PIN 4)
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)
low when the LED pulses.
VDD (PIN 6)
TIMING RESISTOR (PIN 7)
with pin 12 to set the bias current that controls the oscillation
frequency.
MC14568
4
1. This specification also shows V
2. Negative current is defined as coming out of (sourcing) the specified device pin.
3. Alarm (Smoke) Condition is defined as V
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
Symbol
An internal timer is provided that can be used in various
Pin 2 is an input/output pin designed to be connected to
Pin 3 is the low voltage set pin. This pin has an internal
This pin is an open drain output that can be used in various
This pin is the LED cathode connection pin and is driven
This is the positive power supply for the entire IC.
This pin, when tied through a resistor to VDD, works along
V
I
I
low (LED and Horn are off).
DD
I/O
I/O
I/O Current
I/O Charge Dump Duration
I/O Delay
I/O V
Supply Current
IH
, V
IL
(1)
Characteristic
DD
OH
.
of V
V
V
I/O
I/O
DD
= V
= V
15
A
V
- 2.0 V and V
V
V
= +25°C, V
DD
I/O
< V
DD
DD
DD
= 1.0 V
= 9.0 V
13
- 2.0 V
- 2.0 V
= 12 V
; No Alarm (No Smoke) Condition as V
PIN DESCRIPTIONS
OL
DD
After Local Alarm or Test
of 1.0 V at respective currents.
= 9.0 V, V
No Alarm, No Loads
No Alarm, No Loads
V
V
Test Condition
Charge Dump
IH
IL
Alarm Out
, V
, V
No Alarm
Alarm
DD
DD
SS
FEEDBACK (PIN 8)
element.
VSS (PIN 9)
(usually ground).
HORN 1 (PIN 10)
brass and silver).
HORN 2 (PIN 11)
brass and silver).
OSCILLATOR CAP (PIN 12)
works with pin 7 to set the internal oscillation frequency.
SENSITIVITY SET (PIN 13)
for the detect pin (pin 15).
adjust the sensitivity.
GUARD 1/LOW Z (PIN 14)
(pin 15) to reduce leakage currents.
DETECT INPUT PIN (PIN 15)
used in conjunction with an Ionization type element.
GUARD 2/HIGH Z (PIN 16)
pin (pin 15) to reduce leakage currents.
= 9.0 V
= 9.0 V
= 0 V, C
This is the feedback pin used for driving the piezo electric
This is the negative power supply pin for the entire IC
This is one of two pins that drive the horn element (i.e.,
This is one of two pins that drive the horn element (i.e.,
This pin, when tied to a low leakage capacitor to VSS,
This pin is set internally to provide the reference sensitivity
An external resistor from pin 13 to either VDD or VSS can
This pin provides a low impedance guard for the detect pin
This pin functions as a low leakage smoke detect pin when
This pin provides a high impedance guard for the detect
12
= 0.1 µF (Oscillator Pin) R7 = 8.2 mΩf/fn (timing
15
Test
Pin
> V
2
2
2
2
6
13
.
1.33
Min
-75
5.0
3.2
25
—
—
—
—
1.66
Typ
3.0
5.0
—
—
—
—
—
—
Freescale Semiconductor
Max
1.99
1.5
9.0
60
—
—
—
—
12
Sensors
Unit
mA
mA
µA
µA
V
s
s