RE46C165SW16F datasheet(14/30 Pages) MICROCHIP

14 / 30 page

RE46C165/6/7/8

DS22251A-page 14

 2010 Microchip Technology Inc.

3.6

Low Battery Detection

In standby, an internal reference is compared to the

voltage divided VDD supply. A low battery status is

latched at the conclusion of the LED pulse. The horn

will chirp once for 10 ms every 43 seconds, until the

low battery condition no longer exists. The low battery

chirp occurs next to the LED pulse.

The low battery notification does not sound in a local or

remote alarm condition.

3.7

Chamber Fail Detection

In standby, a chamber test is also performed every

43 seconds, by switching to the high gain capacitor C1

and

sensing

the

photo

chamber

background

reflections. Two consecutive chamber test failures will

cause the horn to chirp 3 times for 10 ms spaced

323 ms apart. This will repeat every 42 seconds, as

long as a chamber test fail exists. The failed chamber

test chirps occur ~21 seconds after the LED pulse in

Standby mode (not hush).

The chamber fail notification does not sound in a local

or remote alarm condition.

3.8

Timer Mode

If resistors RADJ1 and RADJ2 (see Typical Application

figure) are in place and a high-to-low transition occurs

on the TEST input, the device enters a timer mode

(10 minutes maximum for RE46C165/6 devices,

1 minute maximum for RE46C167/8). In this mode, the

smoke comparator reference is switched from the

internal VDD – 3.5V reference to the voltage that

appears on VSEN. This allows the sensitivity to be

modified for the duration of the timer period. High gain

operations (push-to-test and chamber test) always use

the internal VDD – 3.5V reference. The chamber test is

performed in Timer mode.

If VSEN is left unconnected or tied to VSS, the Hush

Timer mode operation is inhibited.

If the smoke level causes the reduced sensitivity set

point to be exceeded during this timer period, the unit

will go into a local alarm condition, the horn will sound,

and the Timer mode is cancelled. If an external only

alarm occurs during the Timer mode, the Timer mode

is cancelled.

If the test button is pushed in a standby, reduced

sensitivity mode, the unit is tested normally. Upon

release of the test button, the 10 minute maximum

timer mode counter is reset and restarted.

3.9

Alarm Memory

If a detector has entered a local alarm, when exiting

that local alarm, the alarm memory latch is set. Initially

the LED can be used to visually identify any unit that

had previously been in a local alarm condition. The

LED will flash 3 times spaced 1.3 seconds apart. This

pattern will repeat every 43 seconds. The duration of

the flash is 10 ms. In order to conserve battery power,

this visual indication will stop after a period of 24 hours.

The user will always be able to identify a unit with an

active alarm memory by pressing the push-to-test

button. When this button is active, the horn will chirp

and the LED will pulse on for 10 ms every 250 ms. The

push-to-test alarm will not activate until the alarm

memory is reset.

If the alarm memory condition is set, any time the push-

to-test button is pressed and then released, the alarm

memory latch is reset.

The initial 24 hour visual indication is not displayed if a

low battery condition exits.

3.10

Diagnostic Mode

In addition to the normal function of the TEST input, a

special diagnostic mode is available to calibrate and

test the smoke detector. Taking the TEST pin below

VSS and sourcing ~200 µA 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

Table 3-1 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 ms nominal.

RE46C165SW16F Datasheet(PDF) 14 Page - Microchip Technology

RE46C165SW16F Datasheet(HTML) 14 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Datasheet Download

Link URL