MC145010

*Maximum Ratings are those values beyond which damage to the device may occur. Functional operation should be restricted to the limits in the Electrical Characteristics tables.
** Derating: 12 mW/°C from 25° to 60°C.
*** Derating: 3.5 mW/°C from 25° to 60°C.

This device contains protection circuitry to guard against damage due to high static voltages or electric fields. However, precautions must be taken to avoid applications of any voltage higher than maximum rated voltages to this highimpedance circuit. For proper operation, Vin and Vout should be constrained to the range V_SS 3 (V_in or V_out) 3 V_DD except for the I/O, which can exceed V_DD, and the Test input, which can go below V_SS.

Unused inputs must always be tied to an appropriate logic voltage level (e.g., either V_SS or V_DD). Unused outputs and/or an unused I/O must be left open

The CMOS MC145010 is an advanced smoke detector component containing sophisticated verylowpower analog and digital circuitry. The MC145010 is used with an infrared 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 onchip pushpull drivers and an external piezoelectric transducer.

The variablegain photo amplifier MC145010 allows direct interface to IR detectors (photodiodes). 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. Medium gain is selected during a localsmoke condition. High gain is used during pushbutton test. During standby, the special monitor circuit of MC145010 which periodically checks for degraded chamber sensitivity uses high gain, also.

The I/O pin, in combination with VSS, MC145010 can be used to interconnect up to 40 units for common signaling. An onchip current sink provides noise immunity when the I/O is an input. A localsmoke condition activates the shortcircuitprotected I/O driver, thereby signaling remote smoke to the interconnected units. Additionally, the I/O pin of MC145010 can be used to activate escape lights, enable auxiliary or remote alarms, and/or initiate autodialers.

While in standby, the lowsupply detection circuitry conducts periodic checks using a pulsed load current from the LED pin. The trip point is set using two external resistors. The supply for the MC145010 can be a 9 V battery.A visible LED flash accompanying a pulsating audible alarm indicates a localsmoke condition. A pulsating audible alarm with no LED flash indicates a remotesmoke condition. A beep or chirp occurring virtually simultaneously with an LED flash indicates a lowsupply condition. A beep occurring halfway between LED flashes indicates degraded chamber sensitivity. A lowsupply condition does not affect the smoke detection capability if VDD . 6 V. Therefore,the lowsupply condition and degraded chamber sensitivity of MC145010 can be further distinguished by performing a pushbutton (chamber) test.