RE46C141S16F Datasheet, PDF (9/12 Pages) Microchip Technology – A Subsidiary of Microchip Technology Inc.

RE46C141
CMOS Photoelectric Smoke Detector ASIC with Interconnect
Product Specification
R&E International
A Subsidiary of Microchip Technology Inc.
Low Battery and Chamber Test – In standby an internal reference is compared to the voltage divided VDD supply.
Low battery status is latched at the conclusion of the LED pulse. The horn will chirp for 7.9ms every 32 seconds
until the low battery condition no longer exists. In standby a chamber test is also performed every 32 seconds by
switching to the high gain capacitor C1 and sensing the photo chamber background reflections. Two consecutive
chamber tests failures will also cause the horn to chirp for 7.9mS every 32 seconds. The low battery chirp occurs
next to the LED pulse and the failed chamber test chirp 16.2 seconds later. The low battery and chamber tests
are not performed in a local or remote alarm condition. The low battery alarm threshold is approximately equal to
((5*R15)/R14)+5 where R15 and R16 are in the same units.
Diagnostic Mode – In addition to the normal function of the TEST input a special diagnostic mode is available for
calibration and test of the smoke detector. Taking the TEST pin below VSS and sourcing ~300uA out of the pin
for 1 clock cycle will enable the diagnostic mode. In the diagnostic mode some of the pin functions are redefined.
Refer to the table below for redefined pin functions in the diagnostic mode. In addition in this mode STROBE is
always enabled and the IRED is pulsed at the clock rate of 10.5mS nominal.
Pin Name
IO
LBSET
FEED
COSC
HORNB
LED
Pin Number
7
15
10
12
8
11
Description
Disabled as an output. A high on this pin directs the photo amplifier output to pin C1
(1) or C2 (2), determined by the level on LBSET (15). Amplification occurs during
the IRED active time.
If IO is high then this pin controls the gain capacitor that is used. If LBSET is low
then normal gain is selected and the photo amp output appears on C1 (1). If LBSET
is high then high gain is selected and the photo amp output is on C2 (2).
If LBSET (15) is low then taking this input high will enable hysteresis, which is a
nominal 10% gain increase in normal gain mode.
If desired this pin can be driven by an external clock.
This pin becomes the smoke integrator output. A high level indicates that an alarm
condition has been detected.
The LED pin is used as a low battery indicator. For VDD above the low battery
threshold the open drain NMOS is off. If VDD falls below the threshold the NMOS
turns on.
© 2009 Microchip Technology Inc.
DS22177B-page 9