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document number: mc14568 rev. 1.0, 11/2006 freescale semiconductor product preview ? freescale semiconductor, in c., 2006. all rights reserved. this document contains certain information on a new product. specifications and information herein are subject to change without notice. low-power cmos ionization smoke detector with interconnect and timer the mc14568, when used with an ionization chamber and a small number of external components, will detect smoke. when smoke is sensed, an alarm is sounded via an external piezoelectric trans ducer and internal drivers. this circuit is designed to operate in smoke detect or systems that comply with ul217 and ul268 specifications. an internal oscillator with associated logi c controls the overall functionality by powering down the device for 1.67 seconds and sensing smoke in a 10 ms window. in this way, standby current consumption is reduced to between 5.0 and 9.0 a, thus providing longer battery life. in addition, a networking capability allows as many as 125 to be interconnected so that if any unit senses smoke, all units will sound an alarm. the mc14568 is supplied in a 16-pin dual in-line plastic package and is designed to run on a power supply between 6 to 12 volts. features ? speed-up sampling rate of 40 ms of internal clock period (pin 12) after first detection of smoke ? timer function for reduced sensitivity for a nominal period of 6.43 minutes (10 minutes max) ? high-smoke detection in the ?reduced sensitivity? mode ? internal and external low battery threshold ? internal and external smoke reference settings ? guaranteed power up without random led and horn chirps ? reversed battery protection ? low leakage detect pin ? metal option to add double chirp at end of reduced sensitivity period; default is no chirp ? pb-free packaging designated by suffix code ed ordering information device case no. package pc14568p/r2 648-08 plastic dip pc14568ed/r2 mc14568 p suffix ed suffix (pb-free) plastic dip case 648-08 low-power cmos ionization smoke detector with interconnect and timer figure 1. pin connections 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 timer start i/o low-v set timer out led vdd timing r feedback guard 2 detect input guard 1 sensitivity set oscillator cap horn 2 horn 1 vss
sensors 2 freescale semiconductor mc14568 figure 2. functional block diagram caution: cmos devices have input static protection but are susceptible to dam age when exposed to extremely high static electric al charges . table 1. maximum ratings rating symbol value unit supply voltage range v dd - 0.5 to +15 v input voltage range v in - 0.3 to v dd +0.3 v maximum current (source/sink) by pins 6 (vdd) and pin 9 (vss) i ds 30 ma maximum current input pins i in 10 ma maximum current output pins (pins 2, 4, 5, 10, 11) ? 25 ma maximum current (pin 15) ? 1.0 ma operating temperature range t a 0 to +50 c storage temperature range t stg - 55 to +125 c human body model esd rating v esd 1000 v ( ) vdd 6 3 13 9 2 i/o v dd logic low-v set. sensitivity set. ?supply vss 13 15 16 1 + ? + ? + ? feedback horn 2 horn 1 led 5 v dd power on reset oscillator & timing 12 7 4 v dd osc cap. timing res. timer out timer start 8 11 10
sensors freescale semiconductor 3 mc14568 table 2. electrical characteristics characteristics noted under conditions t a = +25 c, v dd = 9.0 v, v ss = 0 v, c 12 = 0.1 f (oscillator pin) r7 = 8.2 m ? f/fn (timing resistor pin) unless otherwise noted. symbol characteristic test condition test pin min typ max unit v dd supply voltage range operating 6 6.0 9.0 12 v i in detector input current 0 to 40% rh, v in = 0 to 9.0 v 15 ? ? 1.0 pa v os input offset voltage active guard active guard detect comparator 14 ? 15 16 ? 15 15 ? 13 ? ? ? ? ? ? 100 100 50 mv v hys hysteresis no alarm to alarm 13 80 130 160 mv v cm common mode range guard amplifier smoke comparator 14 ? 15 13 ? 15 0.5 0.5 ? ? v dd ? 2.0 v dd ? 2.0 v lo-z hi-z active guard impedance to v cc to v cc 14 16 ? ? 10 500 ? ? k ? t cl oscillator period no alarm alarm 12 1.34 32 1.67 40 2.0 48 s ms timer out pulse width 4 8.0 10 12 ms timer period after pin 1 high to low, no smoke 4 ? 6.43 10 min v th low voltage threshold t a = 0 to 50 c 6 7.2 ? 7.8 v sensitivity adj. voltage v 13 /v dd , pin 3 open circuit 13 48.5 50 51.5 % low battery threshold pin 3 open circuit 3 60.6 63 65.6 % horn output voltage i out = 16 ma, v dd = 9.0 v i out = 16 ma, v dd = 7.2 v i out = -16 ma, v dd = 9.0 v i out = -16 ma, v dd = 7.2 v 10 ? 11 ? ? 8.5 6.3 0.1 ? 8.8 ? 0.5 0.9 ? ? v pw on horn output on time alarm low battery 10 ? 11 450 8.0 500 10 550 12 ms pw off horn output off time alarm alarm low battery 10 ? 11 450 1350 32 500 1500 40 550 1650 48 ms feedback v ih v il 86.3 ? ? ? ? 2.7 v timer start logic levels v ih v il 14.5 ? ? ? ? 2.5 v timer start input current v in = 9.0 v 1 20 ? 80 a timer out output current v out = 0.5 v 4 500 ? ? a i lon led output on current v dd = 7.2 v, v out = 1.0 v 5 10 ? ? ma t lon led output on time no local alarm, not latched 5 8.0 10 12 ms t loff led output off time no alarm, standby no alarm, timer mode 532 8.0 40 10 48 12 s
sensors 4 freescale semiconductor mc14568 pin descriptions timer start (pin 1) an internal timer is provided that can be used in various configurations to allow fo r a period of reduced smoke detector sensitivity (?hush?). when a high-to-low transition occurs at pin 1, the internal timer is reset, the timer mode enabled, and the circuit reset to a no alarm condition. i/o (pin 2) pin 2 is an input/output pin designed to be connected to other smoke units for remote smoke sensing. in a local smoke condition, this pin is driven high by the unit sensing smoke. all other units in the net work will then go into remote smoke mode. low-v set (pin 3) pin 3 is the low voltage set pin. this pin has an internal fixed bias to monitor the battery. using an external resistor from pin 3 to either vdd or vss allows the user to change this bias to some fraction of v dd . timer output (pin 4) this pin is an open drain output that can be used in various timer configurations to alter the ic?s sensitivity. a high to low transition on pin 1 causes this output to pulse for 231 internal clock cycles. led (pin 5) this pin is the led cathode connection pin and is driven low when the led pulses. vdd (pin 6) this is the positive power supply for the entire ic. timing resistor (pin 7) this pin, when tied through a resistor to vdd, works along with pin 12 to set the bias curren t that controls the oscillation frequency. feedback (pin 8) this is the feedback pin used for driving the piezo electric element. vss (pin 9) this is the negative power supply pin for the entire ic (usually ground). horn 1 (pin 10) this is one of two pins that drive the horn element (i.e., brass and silver). horn 2 (pin 11) this is one of two pins that drive the horn element (i.e., brass and silver). oscillator cap (pin 12) this pin, when tied to a low leakage capa citor to vss, works with pin 7 to set the internal oscillation frequency. sensitivity set (pin 13) this pin is set internally to provide the reference sensitivity for the detect pin (pin 15). an external resistor from pi n 13 to either vdd or vss can adjust the sensitivity. guard 1/low z (pin 14) this pin provides a low impedance guard for the detect pin (pin 15) to reduce leakage currents. detect input pin (pin 15) this pin functions as a low leakage smoke detect pin when used in conjunction with an ionization type element. guard 2/high z (pin 16) this pin provides a high impedance guard for the detect pin (pin 15) to reduce leakage currents. i i/o i/o current (1) v i/o = v dd - 2.0 v v i/o = v dd - 2.0 v v i/o = 1.0 v no alarm alarm charge dump 225 -75 5.0 ? ? ? 60 ? ? a ma ma i/o charge dump duration after local alarm or test 2 1.33 1.66 1.99 s i/o delay alarm out 2 ? 3.0 ? s v i/o i/o v ih , v il v ih , v dd = 9.0 v v il , v dd = 9.0 v 23.2 ? ? ? ? 1.5 v i dd supply current v dd = 9.0 v v dd = 12 v no alarm, no loads no alarm, no loads 6? ? 5.0 ? 9.0 12 a 1. this specification also shows v oh of v dd - 2.0 v and v ol of 1.0 v at respective currents. 2. negative current is defined as coming out of (sourcing) the specified device pin. 3. alarm (smoke) condition is defined as v 15 < v 13 ; no alarm (no smoke) condition as v 15 > v 13 . 4 no loads means the ic in standby mode with a 0.1 f capacitor on pin 12 to vss and an 8.2 m ? resistor on pin 7 to vdd with pin 2 tied low (led and horn are off). table 2. electrical characteristics (continued) characteristics noted under conditions t a = +25 c, v dd = 9.0 v, v ss = 0 v, c 12 = 0.1 f (oscillator pin) r7 = 8.2 m ? f/fn (timing resistor pin) unless otherwise noted. symbol characteristic test condition test pin min typ max unit
sensors freescale semiconductor 5 mc14568 device operation in a no smoke condition (i.e., standby mode with detect pin 15 higher than internal reference pin 13), the oscillator operates with a perio d of 1.67 s and the led will flash once every 24-clock periods (or every 40 s). the smoke detect pin (pin 15) is connected to the ionization chamber and leads to the inverting input of a cmos detect comparator. the voltage on this pin is compared to an internal reference voltage on the non- inverting input of the detect comp arator set up by a resistor divider network and a fet switch ( this reference voltage can be increased or decreased by an external resistor from pin 13 to vdd or vss) . periodically (every 1.67 s and for a 10 ms window) power is supplied to the entire ic and a check is made for a smoke condition. during this window the fet switch is turned on and the detect pin voltage (pin 15) is compared to the internal reference voltage (pin 13). if the detect pin is lower than the reference this indicates a smoke condition. a smoke condition speeds up the internal oscillator, which now oscillates with an internal period of 40 ms (the rising edge of the saw tooth periodic signal on pin 12 remains the same while the falling edge falls faster in a smoke condition). furthermore, a smoke condition causes the resistor divider network that sets the smoke detect reference voltage to change in such a way as to make the reference voltage increase by approximately 130 mv (with no external connections to pin 13 or to pin 3). this provides hysteresis and reduces false triggering. this hysteresis is turned off when the ic exits a smoke condition and returns to standby mode. once in a smoke condition, the led will flash every 24- clock cycles (once every second) . the horn (piezo electric element) driver is activated during a smoke condition with a typical on/off time of 160 ms on, 80 ms off. during the off time, the ic re-checks to see if a smoke condition still exists. if no smoke is detected the horn driver is suppressed. during a smoke condition the low voltage battery check is inhibited. no smoke and low battery check during a no smoke condition (i.e., standby mode) the led is pulsed to load the battery every 24-clock cycles (every 40 seconds) and a fraction of the battery voltage (set internally by a resistor divider network and pulsed ?on? by a internal fet) is compared to an internal reference voltage set by a reversed biased zener diode by an internal cmos comparator. the fraction of the supply voltage (pin 3) to be compared to the internal reference voltage for low battery check can be raised or lowered by connecting an external resistor between pin 3 and vdd or pin 3 and vss. if low battery is detected a warning ?chirp? will be sounded by the horn driver once every 24-clock cycles (a low battery condition does not cause the oscillator to speed up as does a smoke condition). low batt ery check will still be performed in reduced sensitivity mode and a low battery chirp will be heard if v dd falls below specified value. timer an internal timer is provided that can be used in various configurations to allow for a period of reduced smoke detector sensitivity.
sensors 6 freescale semiconductor mc14568 figure 3. mc14568 timing diagram for the timer circuit figure 4. mc14568 oscillator waves in stand by and smoke conditions pin 12 osc cap pin 1 timer start internal clock pin 4 timer out pin 5 led check for smoke window 231 clock cycles 6 clock cycles time time time time time time time 10 ms 1.67 s 40 ms 10 ms check for smoke window check for smoke window smoke no smoke
sensors freescale semiconductor 7 mc14568 figure 5. mc14568 typical application diagram note 1: the low voltage set point can be tailored to custom er?s requirement with the us e of an external resistor. note 2: the sensitivity adjustment se t point can be tailored to the customer?s requirement during the timer mode can with the use of an external resistor. note 3: the smoke reference set point can be tailored to the customer?s requirement with the use of an external resistor. 9.0 v 50 k timer mode to other units note 1 330 8.2 m 1.0 f note 2 1 m 1 m test ionization chamber note 3 0.1 f 1.5 m 220 k 0.001 f piezo 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 timo i/o low v timstrt led vdd timing res fdbck hi_z det lo_z smk_ref osc horn 2 horn 1 vss
sensors 8 freescale semiconductor mc14568 package dimensions the mc14568 is supplied in a low-cost, 16-pin dual in-line plastic pa ckage. it is rated for continuous operation over the tem- perature range of 0c to +50c. case 648-08 issue t 16-lead plastic dip page 1 of 3
sensors freescale semiconductor 9 mc14568 package dimensions case 648-08 issue t 16-lead plastic dip page 2 of 3
sensors 10 freescale semiconductor mc14568 package dimensions case 648-08 issue t 16-lead plastic dip page 3 of 3
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