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A5338
Package A, 16-lead DIP
Smoke Detector with Interconnect and Timer
The A5338CA is a low-current, CMOS circuit providing all of the required features for an ionizationtype 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 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 0C to +50C.
Approximate Scale 1:1
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
Typical Application
9V 200 k
50 k 200 k
Push to set 1 To other units 200 2 3 +SUPPLY or -SUPPLY RLV 16 Push to test
TIMER START I/O LOW-V SET
GUARD2
Smoke Chamber
DETECT IN 15
A5338
GUARD1 14 13 12 11 COSC 0.1 F RS +SUPPLY or -SUPPLY
4 TIMER OUT 5 330 6 RT 8.2 M 7 8 LED +SUPPLY TIMING RES FEEDBACK
SENSIVITIVTY SET OSC CAP HORN2
HORN1 10 -SUPPLY 9
1 M 200 k
Horn
1 F
0.001 F RST
Dwg. EC-005A
26110.1
A5338
Smoke Detector with Interconnect and Timer
Functional Block Diagram
I/O
+SUPPLY
VDD
VDD
FEEDBACK HORN2
LOW-V SET
- +
HORN1 LED Logic
SENSITIVITY SET Power-On Reset - -SUPPLY VSS GUARD1 DETECT IN Part Number A5338CA +
TIMING RES OSC CAP TIMER OUT
Oscillator and Timing
Parameter Supply Voltage Range2 Reverse Battery Logic Input Voltage Range2 Logic Input Current Operating Temperature Range (C) Junction Temperature Storage Temperature Range
1CMOS 2Voltages
devices have input static protection, but are susceptible to damage when exposed to extremely high static electrical charges. are references to VSS.
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- GUARD2 TIMER START
+
Selection Guide
Package 16-pin DIP, 300 mil spacing Packing 25 pieces per tube
Absolute Maximum Ratings1
Symbol VDD - VI II TA TJ TS 10.5 V Conditions Min. -0.5 - -0.3 - 0 - -55 - - - - Typ. - - Max. Units 15 20 VDD + 0.3 10 50 150 125 V s V mA C C C
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A5338
Smoke Detector with Interconnect and Timer
Pin-out Diagram
TIMER START I/O LOW-V SET TIMER OUT LED +SUPPLY TIMING RES FEEDBACK
1 2 3 4 5 6 7 8 V DD OSC. & TIMING LOGIC
16 15 14 13 12 11 10 V SS 9
GUARD2 DETECT IN GUARD1 SENSITIVITY SET OSC CAP HORN2 HORN1 -SUPPLY
HORN DRIVER
Dwg. PC-004
Terminal List Table
Number
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Name
TIMER START I/O LOW-V SET TIMER OUT LED +SUPPLY TIMING RES FEEDBACK -SUPPLY HORN1 HORN2 OSC CAP SENSITIVITY SET GUARD1 DETECT IN GUARD2 Logic input for setting device mode.
Function
Logic input/output, where multiple detectors can be connected. 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. Terminal for a resistor, RST, to reduce sensitivity during Timer mode. LED output. Device supply, VDD. Terminal for timing resistor. Feedback from horn external circuit. Device supply, VSS. Horn driver output 1. Horn driver output 2. Terminal for timing oscillator capacitor. Terminal for resistor, RS, to adjust sensitvity for a particular smoke chamber. Terminal for smoke detector guard 1. Terminal for smoke detector input. Terminal for smoke detector guard 2.
26110.1
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A5338
Smoke Detector with Interconnect and Timer
Characteristic Supply Voltage Range Supply Current
ELECTRICAL CHARACTERISTICS1 at TA = 25C, VDD = 9.0 V, VSS = 0 V, COSC = 0.1 F, RT = 8.2 M, unless otherwise noted
Symbol VDD IDD IS VIO VOhys VIC(guard) VIC(det) Active Guard Impedance Zguard Test Pin Test Conditions 6 Operating VDD = 9.0 V, no alarm, no loads 6 VDD = 12 V, no alarm, no loads 15 0 to 40% RH, VI(detect in) = 0 to 9.0 V 14-15 Active guard 16-15 Active guard 15-13 Smoke detect comparator 13 No alarm condition to alarm 14-15 13-15 14 16 Guard amplifier Smoke detect comparator With reference to VSS With reference to VSS No alarm Alarm Min. 6.0 -- -- -1.0 -100 -100 -50 90 2.0 0.5 Typ. 9.0 5.0 -- -- -- -- -- 130 -- -- Max. 12 9.0 12 1.0 100 100 50 170 VDD - 0.5 VDD - 2.0 -- -- 2.00 48 12 8.0 7.8 51.5 0.5 0.9 -- -- 208 12 104 48 -- 2.5 80 -- -- 12 48 12 60 -- -- 1.99 -- --
Detector Input Current2 Input Offset Voltage Hysteresis Common Mode Range
Units V A A pA mV mV mV mV V V s ms ms min V % V V V V ms ms ms s V V A A mA ms s s A mA mA s V s
-- 10 -- 500 1.34 1.67 Oscillator Period tOSC 12 32 40 Oscillator Pulse Width tw(osc) 4 8.0 10 Timer Period ttimer 4 After VTIMER_START transition high-to-low (smoke detected) 5.0 6.5 Low Voltage Threshold VDD(th) 6 TA = 0 to 50C 7.2 -- Sensitivity Adjust Voltage VS 13 VSENSITIVITY_SET/VDD, SENSITIVITY SET pin open circuit 48.5 50 IO(horn) = 16 mA, VDD = 9.0 V -- 0.1 -- -- IO(horn) = 16 mA, VDD = 7.2 V HORNx Output Voltage VO(horn) 10-11 IO(horn) = -16 mA, VDD = 9.0 V 8.5 8.8 IO(horn) = -16 mA, VDD = 7.2 V 6.3 -- Alarm 120 160 HORNx Output ON Time ton(horn) 10-11 Low battery 8.0 10 Alarm 60 80 HORNx Output OFF Time toff(horn) 10-11 Low Battery 32 40 1 4.5 -- VIH(ts) TIMER START Logic Levels VIL(ts) 1 -- -- TIMER START Input Current II(ts) 1 VI(ts) = 9.0 V 20 -- TIMER OUT Output Current IO(to) 4 VO(to) = 0.5 V 500 -- LED Output ON Current ILED 5 VDD = 7.2 V, VLED = 1.0 V 10 -- LED Output ON Time ton(led) 5 8.0 10 No alarm; in Standby mode 32 40 LED Output OFF Time toff(led) 5 No alarm; in Timer mode after VTIMER_START transition high-to-low 8.0 10 2 No alarm, V(IO) = VDD - 2.0 V 25 -- I/O Current2 I(io) -7.5 -- Alarm, V(IO) = VDD - 2.0 V Charge dump, V(io) = 1.0 V 5.0 -- I/O Charge Dump Duration tf(io) 2 After local alarm 1.33 1.66 2 External alarm signal in 3.0 -- I/O Alarm Voltage VI(io) I/O Delay td(io) 2 Alarm signal out -- 3.0 1Alarm (smoke detected) condition is defined as V DETECT_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.
26110.1
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
4
A5338
Smoke Detector with Interconnect and Timer
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 VDD 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 hysteresis and reduces false triggering. An active guard is provided on both GUARDx pins, adjacent to the DETECT IN detector 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 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 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-batterywarning 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 VDD and VSS. The sensitivity can be externally adjusted to the individual characteristics 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 VDD 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 ), 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 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. During 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 lowbattery 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 internal 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 VDD 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.
26110.1
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A5338
Smoke Detector with Interconnect and Timer
Timing Requirements: Nontimer Mode
(Circuit Shown in Typical Application)
1.67 s Internal Oscillator 24 Cycles LED LED Off
10 ms
40 ms
24 Cycles
30 Cycles
LED On Internal Smoke Comparator Ssmple HORNx
12 Cycles
6 Cycles
6 Cycles
HORN On
Low Battery Warning
HORN Off Smoke Chamber Condition VDETECT_IN > VSENSITIVITY_SET (no smoke) VDETECT_IN < VSENSITIVITY_SET (smoke) VDETECT_IN > VSENSITIVITY_SET (no smoke)
Dwg. WC-003
Timing Requirements: Timer Mode
(Circuit Shown in Typical Application)
OSC CAP 1.67 s Internal Oscillator 232 Cycles TIMER START 10 ms
TIMER OUT 6 Cycles LED
Dwg. WC-005-3
Outputs Off (High Z)
LED On
26110.1
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
6
A5338
Smoke Detector with Interconnect and Timer
I/O Operation: V(IO) Input
Remote Alarm Mode 40 ms 1.67 s
Internal Oscillator
4 Cycles
2 Cycles
HORNx
HORN On
HORN Off
I/O
HORN not self-completing when in remote-only alarm
I/O Operation: V(IO) Output
Local Alarm Mode
Internal Oscillator
HORN On HORNx
HORN Off 78 Cycles
I/O
Dwg. WC-004
26110.1
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
7
A5338
Smoke Detector with Interconnect and Timer
Package A, 16-pin DIP
.775 19.69 .735 18.67 16
A B
.014 0.36 .008 0.20
.280 7.11 .240 6.10 A 1 2
.300 .7.62
.430 10.92 MAX
.195 4.95 .115 2.92 .015 2.92 MIN .005 0.13 MIN .070 1.78 .045 1.14 16X .100 .2.54 .150 3.81 .115 2.92
SEATING PLANE
C
.022 .056 .014 .036 .010 [0.25] M C
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
The products described here are manufactured under one or more U.S. patents or U.S. patents pending. 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 performance, 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 systems without express written approval. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use. Copyright(c)2005 AllegroMicrosystems, Inc.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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