5368 ALLEGRO
Document overview
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Technical content
WITH INTERCONNECT AND TIMER The A5368CA is a low-current, CMOS circuit providing all of the required features for an ionization-type smoke detector. A networking capability allows as many as 125 units to be interconnected so that if any unit senses smoke, all units will sound an alarm. In addition, special features are incorporated to facilitate alignment and test of the finished smoke detector. This device is designed to comply with Underwriters Laboratories Specification UL217. The internal oscillator and timing circuitry keeps standby power to a minimum by powering down the device for 1.66 seconds and sensing smoke for only 10 ms. Every 24 on/off cycles, a check is made for low battery condition. By substituting other types of sensors, or a switch for the ionization detector, this very-low power device can be used in numerous other battery-operated safety/security applications. The A5368CA is supplied in a low-cost, 16-pin dual in-line plastic package. It is rated for continuous operation over the temperature range of 0°C to +50°C.
FEATURES
n Interconnect Up to 125 Detectors n Piezoelectric Horn Driver n Guard Outputs for Detector Input n Pulse Testing for Low Battery n Power-ON Reset n Internal Reverse Battery Protection n Internal Timer & Control for Reduced Sensitivity n Built-In Hysteresis Reduces False Triggering n Temporal Horn Pattern Always order by complete part number: A5368CA . Data Sheet 26110.8* ABSOLUTE MAXIMUM RATINGS (Voltages are referenced to VSS) Supply Voltage Range, Input Voltage Range, Operating Temperature Range, Storage Temperature Range, CAUTION: CMOS devices have input static protection but are susceptible to damage when exposed to extremely high static electrical charges. LOGIC OSC. & TIMING HORN DRIVER GUARD DETECT. IN GUARD SENSITIVITY SET OSC. CAP. HORN HORN – SUPPLY TIMER START I / O LOW-V SET TIMER OUT LED + SUPPLY TIMING RES. FEEDBACK V DD Dwg. PC-004 V SS 5368
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000 FUNCTIONAL BLOCK DIAGRAM AND TYPICAL APPLICATION 9 V LOW-V SET – SUPPLY + SUPPLY I / O TIMING RES. FEEDBACK DETECT. IN OSC. CAP. POWER-ON RESET OSCILLATOR & TIMING LOGIC SENSITIVITY SET GUARD GUARD HORN 1 HORN 2 LED TIMER OUT TIMER START V DD 14 15 16 V DD V SS Dwg. FC-001B Copyright ' 1998, Allegro MicroSystems, Inc.
Characteristic Pin Test Conditions Min. Typ. Max. Units Supply Voltage Range 6 Operating 6.0 9.0 12 V Detector Input Current 15 0 to 40% RH, V IN = 0 to 9.0 V Ñ Ñ ±1.0 pA Input Offset Voltage 14-15 Active Guard Ñ Ñ ±100 mV 16-15 Active Guard Ñ Ñ ±100 mV 15-13 Detect Comparator Ñ Ñ ±50 mV Hysteresis 13 No Alarm to Alarm 90 130 170 mV Common Mode Range 14-15 Guard Amplifier 2.0 Ñ V DD - 0.5 V 13-15 Smoke Comparator 0.5 Ñ V DD - 2.0 V Active Guard Impedance 14 to V SS Ñ1 0Ñ k Ω 16 to V SS Ñ 500 Ñ k Ω Oscillator Period 12 No Alarm 1.34 1.67 2.00 s Alarm 32 40 48 ms Oscillator Pulse Width 4 8.0 10 12 ms Timer Period 4 After Pin 1 High-to-Low, No Smoke 8.0 10 12 min Low Voltage Threshold 6 T A = 0 to 50°C 7.2 Ñ 7.8 V Sensitivity Adj. Voltage 13 V 13/VDD, pin 13 open circuit 48.5 50 51.5 % Horn Output Voltage 10-11 I OUT = 16 mA, VDD = 9.0 V Ñ 0.1 0.5 V IOUT = 16 mA, VDD = 7.2 V Ñ Ñ 0.9 V IOUT = -16 mA, VDD = 9.0 V 8.5 8.8 Ñ V IOUT = -16 mA, VDD = 7.2 V 6.3 Ñ Ñ V Horn Output ON Time 10-11 Alarm (see figure, time ÒAÓ) 450 500 550 ms Low Battery 8.0 10 12 ms Horn Output OFF Time 10-11 Alarm (see figure, time ÒBÓ) 450 500 550 ms Alarm (see figure, time ÒCÓ) 1350 1500 1650 ms Low Battery 32 40 48 s Timer Start Logic Levels 1 V IH 4.5 Ñ Ñ V VIL Ñ Ñ 2.5 V Continued next page . . . ELECTRICAL CHARACTERISTICS at TA = +25°C, VDD = 9.0 V, VSS = 0 V, C12 = 0.1 µF, R7 = 8.2 MΩ (unless otherwise noted). NOTE 1: Negative current is defined as coming out of (sourcing) the specified device pin. NOTE 2: Alarm (Smoke) Condition is defined as V 15 < V13; No Alarm (No Smoke) Condition as V15 > V13. 5368 SMOKE DETECTOR WITH INTERCONNECT AND TIMER
Worcester, Massachusetts 01615-0036 (508) 853-5000 Timer Start Input Current 1 V IN = 9.0 V 20 Ñ 80 µA Timer Out Output Current 4 V OUT = 0.5 V 500 Ñ Ñ µA LED Output ON Current 5 V DD = 7.2 V, VOUT = 1.0 V 10 Ñ Ñ mA LED Output ON Time 5 No Local Alarm; Not Latched 8.0 10 12 ms LED Output OFF Time 5 No Alarm, In Standby 32 40 48 s No Alarm, Timer Mode 8.0 10 12 s I/O Current 2 No Alarm, V I/O = VDD - 2.0 V 25 Ñ 60 µA Alarm, VI/O = VDD - 2.0 V -7.5 Ñ Ñ mA Charge Dump, VI/O = 1.0 V 5.0 Ñ Ñ mA I/O Charge Dump Duration 2 After Local Alarm or Test 1.33 1.66 1.99 s I/O Alarm Voltage 2 External ÒAlarmÓ In 3.0 Ñ Ñ V I/O Delay 2 ÒAlarmÓ Out Ñ 3.0 Ñ s Supply Current 6 V DD = 9.0 V, No Alarm, No Loads Ñ 5.0 9.0 µA VDD = 12 V, No Alarm, No Loads Ñ Ñ 12 µA Test Limits Characteristic Pin Test Conditions Min. Typ. Max. Units ELECTRICAL CHARACTERISTICS continued NOTE 1: Negative current is defined as coming out of (sourcing) the specified device pin. NOTE 2: Alarm (Smoke) Condition is defined as V15 < V13; No Alarm (No Smoke) Condition as V15 > V13. CIRCUIT DESCRIPTION The A5368CA is a low-current CMOS circuit providing all of the required features for an ionization-type smoke detector. Oscillator. An internal oscillator operates with a period of 1.67 seconds during no- smoke conditions. Every 1.67 seconds, internal power is applied to the entire circuit and a check is made for smoke. Every 24 clock cycles (40 seconds), the LED is pulsed and a check is made for low battery by comparing V DD to an internal reference. Since very-low currents are used in the device, the oscillator capacitor at pin 12 should be a low-leakage type (PTFE, polysty- rene, or polypropylene). Detector Circuitry. When smoke is detected, the resistor divider network that sets the sensitivity (smoke trip point) is altered to increase the sensitivity set voltage (pin 13) by typically 130 mV with no exter- nal connections to pins 3 or 13. This provides hysteresis and reduces false triggering. An active guard is provided on both pins adjacent to the detector input (pin 15). The voltage at pins 14 and 16 will be within 100 mV of the input. This will keep surface leakage currents to a minimum and provide a method of measuring the input voltage without loading the ionization chamber. The active guard amplifier is not power strobed and thus provides constant protection from surface leakage currents. The detector input has internal diode protection against static damage. Alarm Circuitry. If smoke is detected, the oscillator period changes to 40 ms and the horn is enabled. The horn output is typically 0.5 s horn pattern). During the OFF time, smoke is checked and will inhibit further alarm output if smoke is not sensed. During smoke conditions the low battery alarm is inhibited and the LED is driven at a 1 Hz rate.
TYPICAL APPLICATIONSensitivity Adjust. The detector sensitiv- ity to smoke is set internally by a voltage divider connected between V DD and VSS. The sensitivity can be externally adjusted to the individual characteristics of the ionization chamber by connecting a resistor between pin 13 and V DD , or between pin 13 and VSS. Low Battery. The low battery threshold is set internally by a voltage divider connected between V DD and VSS. The threshold can be increased by connecting a resistor between pin 3 and V DD . The threshold can be de- creased by connecting a resistor between pin 3 and V SS. The battery voltage level is checked every 40 seconds during the 10 mA, 10 ms LED pulse. If an LED is not used, it should be replaced with an equivalent resistor (typically 500 Ω to 1000 Ω ) such that the battery loading remains at 10 mA. Timer. An internal timer is provided that can be used in various configurations to allow for 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. The LED will flash at a 10 second rate. If the level of smoke is increased such that the reduced sensitivity level is reached, the device will go into the alarm condition. The timer, how- ever, will continue to completion of the nominal 10-1/4 minute period (368 clock cycles). If the timer mode is not used, pin 1 should be tied low. I/O. A connection is provided at pin 2 to allow multiple smoke detectors to be commoned. If any single unit detects smoke (I/O is driven high), all connected units will sound their associated horns after a nominal 3 second delay. The LED is suppressed when an alarm is signaled from an interconnected NOTE 1: Use an external resistor to adjust sensitivity for a particular smoke chamber. NOTE 2: Select resistor to reduce sensitivity during timer mode. NOTE 3: A resistor to ground or V DD may be added to this pin to modify low battery voltage threshold. TIMER MODE TO OTHER UNITS NOTE NOTE LOGIC OSC. & TIMING HORN DRIVER V DD Dwg. EC-005A V SS 9 V NOTE 2 200 kW 50 kW 200 kW 200 W 8.2 MW 1 mF 0.1 mF 1 MW 200 kW PUSH TO TEST 0.001 mF 330 W unit. An internal NMOS device acts as a charge dump to aid in appli- cations involving a large (distributed) capacitance on pin 2. The charge dump is activated only on the removal of a local alarm. Testing. On power up, all internal counters are reset. Internal test circuitry allows for low battery check by holding pins 8 and 12 low during power up, then reducing V DD and monitoring HORN1 (pin 10). All functional tests can be accelerated by driving pin 12 with a 2 kHz square wave. The 10 ms strobe period must be maintained for proper operation of the comparator circuitry. 5368 SMOKE DETECTOR WITH INTERCONNECT AND TIMER
Worcester, Massachusetts 01615-0036 (508) 853-5000 TIMING DIAGRAMS IN TYPICAL APPLICATION NON-TIMER MODE TIMER MODE
19 CLOCK CYCLES
1.67 s NO ALARM NO LOW BATTERY STANDBY MODE 10 ms 40 ms
24 CLOCK CYCLES
V15 > V13 (NO SMOKE) V15 < V13 (SMOKE) V12 OSC. CAP INTERNAL CLOCK LED SMOKE COMPARATOR SMOKE CHAMBER HORN SAMPLE ALARM NO LOW BATTERY
30 CLOCK CYCLES
"A" ALARM AND LOW BATTERY NO ALARM LOW BATTERY Dwg. WC-003-2
12 CLOCK
"B"
13 CLOCK
73 CLOCK CYCLESI/O
"C" 1.67 s 10 ms V12 OSC. CAP INTERNAL CLOCK LED HORN Dwg. WC-005-1 LED ON TIMER START TIMER OUT
6 CLOCK CYCLES
368 CLOCK CYCLES
OUTPUTS OFF (HIGH Z) I/O CHARGE DUMP I/O
1.67 s40 ms
72 CLOCK CYCLES
Dwg. WC-004-1 HORN HORN CYCLE NOT SELF COMPLETING AFTER REMOTE OR LOCAL ALARM CONDITION IS REMOVED SINGLE HORN PULSE IN PROGRESS IS SELF COMPLETING AFTER LOCAL ALARM CONDITION IS REMOVED SHADED AND UNSHADED AREAS ARE DIFFERENT TIME SCALES I/O CHARGE DUMP 5368 SMOKE DETECTOR WITH INTERCONNECT AND TIMER
Worcester, Massachusetts 01615-0036 (508) 853-5000 Dimensions in Inches (controlling dimensions) Dimensions in Millimeters (for reference only) NOTES: 1. Lead thickness is measured at seating plane or below. 2. Lead spacing tolerance is non-cumulative. 3. Exact body and lead configuration at vendor’s option within limits shown. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the design of its products. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use. 0.014 0.008 0.300 BSC Dwg. MA-001-16A in 0.430 MAX 1 8 0.280 0.240 0.210 MAX 0.070 0.045 0.015 MIN 0.022 0.014 0.100 BSC 0.005 MIN 0.150 0.115 0.775 0.735 0.355 0.204 7.62 BSC Dwg. MA-001-16A mm 10.92 MAX 1 8 7.11 6.10 5.33 MAX 1.77 1.15 0.39 MIN 0.558 0.356 2.54 BSC 0.13 MIN 3.81 2.93 19.68 18.67