A5338

A5338 ALLEGRO

Document overview

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Technical content

Features

„ Interconnect up to 125 detectors „ Piezoelectric horn driver „ Guard outputs for detector input „ Pulse testing for low battery „ Power-on reset „ Internal reverse battery protection „ Internal timer and control for reduced sensitivity „ Built-in hysteresis reduces false triggering Smoke Detector with Interconnect and Timer A5338 Package A, 16-lead DIP Approximate Scale 1:1 The A5338CA 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 facili- tate 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 A5338CA 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. Typical Application Dwg. EC-005A

9 V 200 kΩ

50 kΩ 200 kΩ 200 Ω A5338 8.2 M RT Ω 1 μF 0.1 μ F 1 MΩ 200 kΩ 0.001 μF 330 Ω To other units TIMER START GUARD2 DETECT IN GUARD1 SENSIVITIVTY SET OSC CAP HORN2 HORN1 –SUPPLY LOW-V SET TIMER OUT LED +SUPPLY +SUPPLY or –SUPPLY +SUPPLY or –SUPPLY TIMING RES FEEDBACK I/O Push to test Smoke Chamber Horn Push to set RS RST RLV COSC

26110.1 Worcester, Massachusetts 01615-0036 (508) 853-5000

115 Northeast Cutoff, Box 15036

www.allegromicro.com Allegro MicroSystems, Inc. Smoke Detector with Interconnect and TimerA5338 Selection Guide Part Number Package Packing A5338CA 16-pin DIP, 300 mil spacing 25 pieces per tube Parameter Symbol Conditions Min. Typ. Max. Units Supply Voltage Range2 VDD –0.5 – 15 V Reverse Battery – 10.5 V – – 20 s Logic Input Voltage Range2 VI –0.3 VDD + 0.3 V Logic Input Current I I – – 10 mA Operating Temperature Range (C) T A 0 – 50 °C Junction Temperature T J – – 150 °C Storage Temperature Range T S –55 – 125 °C 1CMOS devices have input static protection, but are susceptible to damage when exposed to extremely high static electrical charges. 2Voltages are references to VSS. Absolute Maximum Ratings1 LOW-V SET –SUPPLY +SUPPLY I/O TIMING RES FEEDBACK DETECT IN OSC CAP Power-On Reset Oscillator and Timing Logic SENSITIVITY SET GUARD1 GUARD2 HORN1 HORN2 LED TIMER OUT TIMER START VDDVDD VSS Functional Block Diagram

www.allegromicro.com Allegro MicroSystems, Inc. Smoke Detector with Interconnect and TimerA5338 Terminal List Table Pin-out Diagram Number Name Function 1 TIMER START Logic input for setting device mode. 2 I/O Logic input/output, where multiple detectors can be connected.

3 LOW-V SET Terminal for a resistor, RLV, to the –SUPPLY pin (VSS) or to the +SUPPLY pin (VDD),

which may be added to modify the battery Low Voltage Threshold, VDDL. 4 TIMER OUT Terminal for a resistor, RST, to reduce sensitivity during Timer mode. 5 LED LED output. 6 +SUPPLY Device supply, V DD. 7 TIMING RES Terminal for timing resistor. 8 FEEDBACK Feedback from horn external circuit. 9 –SUPPLY Device supply, V SS. 10 HORN1 Horn driver output 1. 11 HORN2 Horn driver output 2. 12 OSC CAP Terminal for timing oscillator capacitor. 13 SENSITIVITY SET Terminal for resistor, RS, to adjust sensitvity for a particular smoke chamber. 14 GUARD1 Terminal for smoke detector guard 1. 15 DETECT IN Terminal for smoke detector input. 16 GUARD2 Terminal for smoke detector guard 2. 71 0 LOGIC OSC. & TIMING HORN DRIVER GUARD2 DETECT IN GUARD1 SENSITIVITY SET OSC CAP HORN2 HORN1 –SUPPLY TIMER START I/O LOW-V SET TIMER OUT LED +SUPPLY TIMING RES FEEDBACK V DD Dwg. PC-004 VSS

www.allegromicro.com Allegro MicroSystems, Inc. Smoke Detector with Interconnect and TimerA5338 ELECTRICAL CHARACTERISTICS1 at TA = 25°C, VDD = 9.0 V, VSS = 0 V, COSC = 0.1 μF, RT = 8.2 MΩ, unless otherwise noted Characteristic Symbol Test Pin Test Conditions Min. Typ. Max. Units Supply Voltage Range V DD 6 Operating 6.0 9.0 12 V Supply Current I DD 6 VDD = 9.0 V, no alarm, no loads — 5.0 9.0 μA VDD = 12 V, no alarm, no loads — — 12 μA Detector Input Current2 IS 15 0 to 40% RH, V I(detect in) = 0 to 9.0 V –1.0 — 1.0 pA Input Offset Voltage V IO 14-15 Active guard –100 — 100 mV 16-15 Active guard –100 — 100 mV 15-13 Smoke detect comparator –50 — 50 mV Hysteresis V Ohys 13 No alarm condition to alarm 90 130 170 mV Common Mode Range VIC(guard) 14-15 Guard amplifier 2.0 — VDD - 0.5 V VIC(det) 13-15 Smoke detect comparator 0.5 — VDD - 2.0 V Active Guard Impedance Z guard

14 With reference to V SS —1 0— Ω

16 With reference to V SS — 500 — Ω

Oscillator Period t OSC 12 No alarm 1.34 1.67 2.00 s Alarm 32 40 48 ms Oscillator Pulse Width t w(osc) 4 8.0 10 12 ms Timer Period t timer 4 After V TIMER_START transition high-to-low (smoke detected) 5.0 6.5 8.0 min Low Voltage Threshold V DD(th) 6T A = 0 to 50°C 7.2 — 7.8 V Sensitivity Adjust Voltage V S 13 V SENSITIVITY_SET/VDD, SENSITIVITY SET pin open circuit 48.5 50 51.5 % HORNx Output Voltage V O(horn) 10-11 IO(horn) = 16 mA, VDD = 9.0 V — 0.1 0.5 V IO(horn) = 16 mA, VDD = 7.2 V — — 0.9 V IO(horn) = –16 mA, VDD = 9.0 V 8.5 8.8 — V IO(horn) = –16 mA, VDD = 7.2 V 6.3 — — V HORNx Output ON Time t on(horn) 10-11 Alarm 120 160 208 ms Low battery 8.0 10 12 ms HORNx Output OFF Time t off(horn) 10-11 Alarm 60 80 104 ms Low Battery 32 40 48 s TIMER START Logic Levels VIH(ts) 1 4.5 — — V VIL(ts) 1 — — 2.5 V TIMER START Input Current I I(ts) 1V I(ts) = 9.0 V 20 — 80 μA TIMER OUT Output Current I O(to) 4V O(to) = 0.5 V 500 — — μA LED Output ON Current I LED 5V DD = 7.2 V, VLED = 1.0 V 10 — — mA LED Output ON Time t on(led) 5 8.0 10 12 ms LED Output OFF Time t off(led) 5 No alarm; in Standby mode 32 40 48 s No alarm; in Timer mode after VTIMER_START transition high-to-low 8.0 10 12 s I/O Current2 I(io) 2 No alarm, V (IO) = VDD - 2.0 V 25 — 60 μA Alarm, V(IO) = VDD - 2.0 V -7.5 — — mA Charge dump, V(io) = 1.0 V 5.0 — — mA I/O Charge Dump Duration t f(io) 2 After local alarm 1.33 1.66 1.99 s I/O Alarm Voltage V I(io) 2 External alarm signal in 3.0 — — V I/O Delay t d(io) 2 Alarm signal out — 3.0 — s 1Alarm (smoke detected) condition is defined as VDETECT_IN < VSENSITIVITY_SET; No-Alarm (no smoke detected) condition is defined as VDETECT_IN > VSENSITIVITY_SET. 2Negative current is defined as coming out of (sourcing) the specified device pin.

www.allegromicro.com Allegro MicroSystems, Inc. Smoke Detector with Interconnect and TimerA5338 Functional Description The A5338 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 s during no-smoke conditions. Every 1.67 s, internal power is applied to the entire circuit and a check is made for smoke. Every 24 oscillator cycles (40 s total), the LED is pulsed and a check is made for low battery by comparing V DD to an internal reference. Because very low currents are used in the device, the oscillator capacitor, COSC, at the OSC CAP pin should be a low-leakage type (PTFE, polystyrene, or polypropylene). Detector Circuitry. When smoke is detected, the resistor divider network that sets the sensitivity (smoke trip point) is altered to increase the voltage on the SENSITIVITY SET pin by 130 mV typical, when there are no external connections to the SENSITIVITY SET pin or LOW-V SET pin. This provides hys- teresis and reduces false triggering. An active guard is provided on both GUARDx pins, adjacent to the DETECT IN detec- tor input pin. The voltage at the GUARDx pins will be within 100 mV of DETECT IN. 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 protec- tion 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 160 ms ON, and 80 ms OFF, typical. During the OFF time, smoke is again checked and the circuit will inhibit further horn output if smoke is not sensed. During smoke conditions, the low-battery- warning is inhibited. The LED is driven at a 1 Hz rate, and will only turn ON while the horn outputs are in the OFF state. Sensitivity Adjust. The detector sensitivity to smoke is set internally by a voltage divider connected between V DD and VSS. The sensitivity can be externally adjusted to the individual char- acteristics of the ionization chamber by connecting a resistor, RS, between the SENSITIVITY SET pin and +SUPPLY , or between SENSITIVITY SET pin and –SUPPLY . 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, RLV , between the LOW-V SETpin and +SUPPLY . The threshold can be decreased by connecting RLV between LOW-V SETpin and –SUPPLY . The battery voltage level is checked every 40 s during the 10 mA, 10 ms LED pulse. If an LED is not used, it should be replaced with an equivalent resistor (typically 500 to 1000 Ω), such that the bat- tery 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 mode. When a high-to-low transition occurs at the TIMER START pin, the internal timer is reset, Timer mode is enabled, and the circuit is reset to a no-alarm condition. Dur- ing Hush mode, the LED will flash at a 10 s 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, however, will continue to completion of the nominal 6.5 minute period (232 oscillator cycles). If Timer mode is not used, the TIMER START pin should be tied low. While in Hush mode, the battery is checked. If a low-battery condition is detected, the low- battery warning chirp will be activated. I/O. The I/O pin provides a terminal 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 s delay. The LED is suppressed when an alarm is signaled from another interconnected unit. An inter- nal NMOS device acts as a charge dump to aid in applications involving a large (distributed) capacitance on the I/O pin. 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 the FEEDBACK and OSC CAP pins low during power-up, then reducing V DD and monitoring HORN1. All functional tests can be accelerated by driving OSC CAP with a 2 kHz square wave. The 10 ms strobe period must be maintained for proper operation of the comparator circuitry.

www.allegromicro.com Allegro MicroSystems, Inc. Smoke Detector with Interconnect and TimerA5338 1.67 s 10 ms 40 ms

24 Cycles

Dwg. WC-003 LED Off LED On HORN On HORN Off LED Dwg. WC-005-3 LED On TIMER START TIMER OUT Outputs Off (High Z)

12 Cycles 6 Cycles 6 Cycles

30 Cycles

VDETECT_IN > VSENSITIVITY_SET (no smoke) VDETECT_IN > VSENSITIVITY_SET (no smoke) VDETECT_IN < VSENSITIVITY_SET (smoke) 1.67 s 10 ms

232 Cycles

6 Cycles

Timing Requirements: Nontimer Mode (Circuit Shown in Typical Application) Timing Requirements: Timer Mode (Circuit Shown in Typical Application)

www.allegromicro.com Allegro MicroSystems, Inc. Smoke Detector with Interconnect and TimerA5338 HORN not self-completing when in remote-only alarm I/O 40 ms 1.67 s I/O Local Alarm Mode Remote Alarm Mode Dwg. WC-004 Internal Oscillator HORNx Internal Oscillator HORNx

2 Cycles4 Cycles

78 Cycles

I/O Operation: V(IO) Input I/O Operation: V(IO) Output

www.allegromicro.com Allegro MicroSystems, Inc. Smoke Detector with Interconnect and TimerA5338 Package A, 16-pin DIP Allegro MicroSystems, Inc. reserves the right to make, from time to time, such de par tures from the detail spec i fi ca tions as may be required to permit improvements in the per for mance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro products are not authorized for use as critical components in life-support devices or sys tems without express written approval. The in for ma tion in clud ed herein is believed to be ac cu rate and reliable. How ev er, Allegro MicroSystems, Inc. assumes no re spon si bil i ty for its use; nor for any in fringe ment of patents or other rights of third parties which may result from its use. Copyright©2005 AllegroMicrosystems, Inc. .070 .045 1.78 1.14 .150 .115 3.81 2.92 .195 .115 4.95 2.92 .014 .008 0.36 0.20 .430 MAX 10.92 .015 MIN 2.92 .005 MIN 0.13 .775 .735 19.69 18.67 A B CSEATING PLANE .022 .014 .056 .03616X .010 [0.25] M C .100 .2.54 .300 .7.62 .280 .240 7.11 6.10 A Preliminary dimensions, for reference only Dimensions in inches Metric dimensions (mm) in brackets, for reference only (reference JEDEC MS-001 BB) Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown A Terminal #1 mark area