Electronic Components Datasheet Search |
|
RE46C145S16F Datasheet(PDF) 9 Page - Microchip Technology |
|
RE46C145S16F Datasheet(HTML) 9 Page - Microchip Technology |
9 / 26 page 2009-2012 Microchip Technology Inc. DS22181C-page 9 RE46C145 3.0 DEVICE DESCRIPTION 3.1 Standby Internal Timing With the external components specified in the Typical Application for R12 and C5, the internal oscillator has a nominal period of 10 ms. Normally the analog circuitry is powered down to minimize standby current (typically 4 µA at 9V). Once every 10 seconds the detection circuitry (normal gain) is powered up for 10 ms. Prior to completion of the 10 ms period, the IRED pulse is active for 100 µs. At the conclusion of the 10 ms period, the photo amplifier is compared to an internal reference to determine the chamber status and latched. If a smoke condition is present, the period to the next detection decreases and additional checks are made. Three consecutive smoke detections will cause the device to go into alarm, and the horn circuit and interconnect will be active. Once every 43 seconds the status of the battery volt- age is checked. This status is checked and latched at the conclusion of the LED pulse. In addition, once every 43 seconds the chamber is activated and, using the high gain mode (capacitor C1), a check of the chamber is made by amplifying background reflections. If either the low battery or the photo chamber test fails, the horn will chirp for 10 ms every 43 seconds. The oscillator period is determined by the values of R9, R12 and C5 (see Typical Application). The oscillator period is as follows: EQUATION 3-1: 3.2 Smoke Detection Circuitry A comparator compares the photo amp output to an internal reference voltage. If the required number of consecutive smoke conditions is met, the device will go into local alarm and the horn will be active. In local alarm, the C2 gain is internally increased by approximately 10% to provide alarm hysteresis. 3.3 Push-to-Test Operation If the TEST input pin is activated (VIH), after one internal clock cycle, the smoke detection rate increases to once every 330 ms. In this mode, the high-gain capacitor C1 is selected, and background reflections are used to simulate a smoke condition. After the required consecutive detections, the device will go into a local alarm condition. When the TEST input is deactivated (VIL) and after one clock cycle, the normal gain capacitor C1 is selected. The detection rate continues at once every 330 ms until three consecutive no smoke conditions are detected. At this point, the device returns to standby timing. 3.4 LED Operation In standby, the LED is pulsed on for 10 ms every 43 seconds. In a local alarm condition or the push-to- test alarm, the LED pulse frequency is increased to once every .5 seconds. In the case of a remote alarm, the LED is not active. In the Timer mode of operation, the LED is pulsed on for 10 ms every 10 seconds. 3.5 Interconnect Operation The bidirectional I/O pin allows for interconnection of multiple detectors. In a local alarm condition, this pin is driven high immediately through a constant current source. Shorting this output to ground will not cause excessive current. The I/O is ignored as an input during a local alarm. The I/O pin also has an NMOS discharge device that is active for 1 second after the conclusion of any type of local alarm. This device helps to quickly discharge any capacitance associated with the interconnect line. If a remote active-high signal is detected, the device goes into remote alarm and the horn will be active. Internal protection circuitry allows for the signaling unit to have a higher supply voltage than the signaled unit, without excessive current draw. The interconnect input has a 670 ms nominal digital filter. This allows for interconnection to other types of alarms (carbon monoxide, for example) that may have a pulsed interconnect signal. Note: All timing references are nominal. See Electrical Characteristics for limits. T= TR +TF Where: TR = .6931 x R12 x C5 TF = .6931 x R9 x C5 |
Similar Part No. - RE46C145S16F |
|
Similar Description - RE46C145S16F |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |