MC145018 Motorola, MC145018 Datasheet - Page 5

• Manufacturer Part Number: MC145018
• Description: LONIZATION SMOKE DETECTOR IC WITH INTERCONNECT AND TEMPORAL HORN DRIVER
• Manufacturer: Motorola

TIMING
period of 1.65 seconds during no–smoke conditions. Each
1.65 seconds, internal power is applied to the entire IC and a
check is made for smoke, except during LED pulse, Low Bat-
tery Alarm Chirp, or Horn Modulation (in smoke). Every 24
clock cycles a check is made for low battery by comparing
V
are used in the oscillator, the oscillator capacitor should be of
a low leakage type.
DETECT CIRCUITRY
41.67 ms and the piezoelectric horn oscillator circuit is
enabled. The horn output is modulated 500 ms on, 500 ms
off. During the off time, smoke is again checked and will
inhibit further horn output if no smoke is sensed. During local
smoke conditions the low battery alarm is inhibited, but the
LED pulses at a 1.0 Hz rate. In remote smoke, the LED is
inhibited as well.
detect input. The voltage at these pins will be within 100 mV
of the input signal. This will keep surface leakage currents to
a minimum and provide a method of measuring the input volt-
age without loading the ionization chamber. The active guard
op amp is not power strobed and thus gives constant protec-
tion from surface leakage currents. Pin 15 (the Detect input)
has internal diode protection against static damage.
INTERCONNECT
connect up to 40 remote units for common signaling. A Local
Smoke condition activates a current limited output driver,
thereby signaling Remote Smoke to interconnected units. A
small current sink improves noise immunity during non–
smoke conditions. Remote units at lower voltages do not
OTHER
DD
UNITS
Motorola Sensor Device Data
The internal oscillator of the MC145018 operates with a
If smoke is detected, the oscillator period becomes
An active guard is provided on both pins adjacent to the
The I/O (Pin 2), in combination with V
TO
to an internal zener voltage. Since very small currents
0.1 F
+
9 V
8.2 M
330
Figure 5. Typical Application as Ionization Smoke Detector
Freescale Semiconductor, Inc.
For More Information On This Product,
1
2
3
4
5
6
7
8
SS
MC145018
, is used to inter-
Go to: www.freescale.com
16
DEVICE OPERATION
15
14
13
12
11
10
9
1.5 M *
0.001 F
draw excessive current from a sending unit at a higher volt-
age. The I/O is disabled for three oscillator cycles after power
up, to eliminate false alarming of remote units when the bat-
tery is changed.
SENSITIVITY/LOW BATTERY THRESHOLDS
levels are set internally by a common voltage divider (see
Figure 1) connected between V
can be altered by external resistors connected from pins 3 or
13 to either V
due to the common voltage divider network. The sensitivity
threshold can also be set by adjusting the smoke chamber
ionization source.
TEST MODE
strobed, adjustments for sensitivity or low battery level could
be difficult and/or time–consuming. By forcing Pin 12 to V
the power strobing is bypassed and the output, Pin 1,
constantly shows smoke/no smoke. Pin 1 = V
In this mode and during the 10 ms power strobe, chip current
rises to approximately 50 A.
LED PULSE
ing the LED pulse. The battery is loaded via a 10 mA pulse
for 11.6 ms. If the LED is not used, it should be replaced with
an equivalent resistor such that the battery loading remains
at 10 mA.
HYSTERESIS
sets sensitivity is altered to increase sensitivity. This yields
approximately 100 mV of hysteresis and reduces false
triggering.
Both the sensitivity threshold and the low battery voltage
Since the internal op amps and comparators are power
The 9–volt battery level is checked every 40 seconds dur-
When smoke is detected, the resistor/divider network that
DD
220 k *
or V
SS
0.1 F
. There will be a slight interaction here
1 M
*NOTE: Component values may
change depending on type of
piezoelectric horn used.
DD
and V
SS
1 M
. These voltages
MC145018
DD
for smoke.
TEST
5
SS
,