Archived by Freescale Semiconductor, Inc., 2009
Photoelectric Smoke Detector IC
with I/O For Line-Powered
The CMOS MC145011 is an advanced smoke detector component containing
sophisticated very-low-power analog and digital circuitry. The IC is used with an in-
frared photoelectric chamber. Detection is accomplished by sensing scattered light
from minute smoke particles or other aerosols. When detection occurs, a pulsating
alarm is sounded via on-chip push-pull drivers and an external piezoelectric trans-
The variable-gain photo amplifier allows direct interface to IR detectors (photo-
diodes). Two external capacitors C1 and C2, C1 being the larger, determine the
gain settings. Low gain is selected by the IC during most of the standby state. Me-
dium gain is selected during a local-smoke condition. High gain is used during push
button test. During standby, the special monitor circuit which periodically checks for
degraded chamber sensitivity uses high gain, also.
The I/O pin, in combination with VSS, can be used to interconnect up to 40 units
for common signaling. An on-chip current sink provides noise immunity when the I/
O is an input. A local-smoke condition activates the short-circuit-protected I/O driv-
er, thereby signaling remote smoke to the interconnected units. Additionally, the I/
O pin can be used to activate escape lights, enable auxiliary or remote alarms, and/
or initiate auto-dialers.
While in standby, the low-supply detection circuitry conducts periodic checks us-
ing a load current from the LED pin. The trip point is set using two external resistors.
The supply for the MC145011 must be a dc power source capable of supplying 35
mA continuously and 45 mA peak. When the MC145011 is in standby, an external
LED is continuously illuminated to indicate that the device is receiving power.
An extinguished LED accompanied by a pulsating audible alarm indicates a lo-
cal-smoke condition. A pulsating audible alarm with the LED illuminated indicates
a remote-smoke condition. A beep or chirp indicates a low-supply condition or de-
graded chamber sensitivity. A low-supply condition does not affect the smoke de-
tection capability if VDD ≥ 6 V. Therefore, the low-supply condition and degraded
chamber sensitivity can be distinguished by performing a push button (chamber)
test. This circuit is designed to operate in smoke detector systems that comply with
UL217 and UL268 specifications.
• Operating Voltage Range: 6 to 12 V
• Operating Temperature Range: -10 to 60°C
• Average Standby Supply Current (Visible LED Illuminated): 20 mA
• Power-On Reset Places IC in Standby Mode (Non-Alarm State)
• Electrostatic Discharge (ESD) and Latch Up Protection Circuitry on All Pins
• Chip Complexity: 2000 FETs, 12 NPNs, 16 Resistors, and 10 Capacitors
• Pb-Free Packaging Designated by Suffix Code ED
Rev. 5.0, 11/2006
DETECTOR IC WITH I/O FOR
ED SUFFIX (PB-FREE)
Figure 1. Pin Connections
Freescale Semiconductor, Inc. reserves the right to change the detail specifications, as may be required, to
permit improvements in the design of its products.
© Freescale Semiconductor, Inc., 2006. All rights reserved.