A5303

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Description

The A5303 is a low-current BiCMOS photoelectric smoke detector circuit with ultra-low standby current and can operate for 10 years powered by inexpensive batteries. This device can be used with an infrared optical chamber to sense light scattered from smoke particles. A networking capability allows units to be interconnected so that if any unit senses smoke all units will sound an alarm. Special features are incorporated in the design to facilitate calibration and testing of the finished detector. A variable-gain photoamplifier can be directly interfaced to an infrared emitter-detector pair. The amplifier gain levels are determined by two external capacitors and are internally selected depending on the operating mode. Low gain is selected during standby and timer modes. During a local alarm, this low gain is increased (internally) by approximately 45% to provide hysteresis. High gain is used during pushbutton test and to periodically monitor the chamber sensitivity during standby. The internal oscillator and timing circuitry minimize standby power by sensing for smoke for only 100 μs once every 10 s. A special three-stage-speedup sensing scheme is incorporated to minimize the time to an audible alarm and also to reduce false triggering. Chamber sensitivity is periodically monitored and two consecutive cycles of degraded sensitivity are required for a warning signal to occur. The A5303 is supplied in a thin profile (<1.2 mm overall height) 20-pin TSSOP package (0.65 mm nominal lead pitch). The package is lead (Pb) free with 100% matte tin leadframe plating. 5303-DS Features and Benefits ▪ Low average standby current allows 10-year battery life ▪ 2.3 to 5.5 V operating range ▪ Interconnect option ▪ Logic outputs to control an external sound IC ▪ Low battery detection and warning ▪ Chamber sensitivity test and warning ▪ Triple horn-chirp to distinguish chamber warning ▪ Power-on reset (POR) ▪ Digital filter on I/O provides significant noise immunity ▪ Timer (hush) mode for enabling reduced sensitivity period ▪ Built-in circuits to reduce false triggering ▪ ESD protection circuitry on all pins ▪ Temporal Horn Pattern, per UL217, NFPA72, ISO8201 ▪ Latching alarm indicator identifies alarm-initiating devices Photoelectric Smoke Detector with Interconnect, Timer, and Latching Alarm Indicator Package: 20-pin TSSOP (suffix LE) Not to scale A5303 Typical Application Diagram Control Logic SOUT0 VDD TEST 56 nF 5.6 nF DETECT Gain Select STROBE IREDVDD OSC Timing Low Batt 1.2 V 3 V 100 μF LED VSS 560 Ω 200 kΩ 10 μF VDD - 1.6 V OSCCAP 1500 pf Push-to-test HUSH Connect HUSH to VSS to disable timer mode Connect to allow timer (hush) mode operation ISET LVSET Low Batt Sample A A A resistor connected between this pin and VDD or VSS adjusts the low-battery thresholdSOUT1 Voice IC outputs 10 ΜΩ100 kΩ SOUT2 TRES I/O 220 Ω To / from other units VDD VDDVDD BLINK In standby, BLINK = VDD causes LED to blink, BLINK = VSS causes LED not to blinkHORN Output to optional boost converter to drive a piezo horn Smoke Chamber Red LED B B 5 k Ω 3 kΩ 3 Ω 1 kΩ

Photoelectric Smoke Detector with Interconnect, Timer, and Latching Alarm IndicatorA5303 2Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A. Selection Guide Part Number Pb-free and RoHS Package Packing A5303SLE-T Yes 20-pin TSSOP (JEDEC MO-153AC) 75 pieces / tube A5303SLETR-T Yes 20-pin TSSOP (JEDEC MO-153AC) 4000 pieces / reel Absolute Maximum Ratings Characteristic Symbol Notes Rating Units Supply Voltage Range V DD Referenced to VSS –2.3 to 6 V DC Input Voltage Range V IN Referenced to VSS –0.3 to 6 V Operating Ambient Temperature Range T A Allegro Range S –20 to 85 ºC Maximum Junction Temperature T J(max) 150 ºC Storage Temperature Range T stg –55 to 150 ºC Pin-out Diagram Thermal Characteristics Characteristic Symbol Test Conditions* Value Units Package Thermal Resistance R θJA Estimated, single-layer PCB, minimal exposed copper area 127 ºC/W *Additional thermal information available on Allegro website. Terminal List Number Name Function

1 SOUT1 Logic push-pull output for controlling an external sound IC

2 SOUT0 Logic push-pull output for controlling an external sound IC

3 I/O Input-output to interconnected detectors

4 BLINK Logic input for enabling/disabling the LED blink during standby

5 HUSH Input for photoamplifier timer mode reference; can also disable timer mode

6 ISET A resistor on this pin connected to VSS sets the IRED output current

7 VDD Positive supply voltage

8 IRED Terminal to drive smoke chamber IR LED

9 STROBE Strobed supply (V

DD – 2 V) for photoamplifier low-side reference

10 DETECT Photoamplifier input

11 C2 Sets photoamplifier gain in standby mode

12 C1 Sets photoamplifier gain in supervisory mode

13 LVSET Optionally used with a resistor to adjust the low-battery threshold

14 TRES Connection for resistor to set clock times/frequency

15 VSS Negative supply voltage

16 OSC CAP Connection for capacitor and resistor to set clock times/frequency

17 TEST Enables push-to-test mode; starts timer mode, if enabled

18 HORN Logic output which optionally enables a boost converter to drive a horn

19 LED Output to drive visible LED

20 SOUT2 Logic push-pull output for controlling an external sound IC

Photoelectric Smoke Detector with Interconnect, Timer, and Latching Alarm IndicatorA5303 3Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. DC ELECTRICAL CHARACTERISTICS1 Valid at TA = 25°C, VDD = 2.3 to 5.5 V, configured as in Typical Application Diagram (unless otherwise noted) Characteristics Symbol Test Conditions Min. Typ. 2 Max. Unit Supply Voltage Range V DD Operating 2.3 3.0 5.5 V Operating Supply Current I DD During standby, STROBE off – 2.3 5.0 μA During STROBE on, IRED off – 210 300 μA During STROBE on, IRED on – 220 300 μA Input Current I IN BLINK, C1, C2, DETECT, OSC CAP, TRES (pulldown off) –100 0 100 nA TEST Pulldown Current I IN(TEST) VTEST = VDD = 3 V – 3.5 – μA Logic Voltage Low V I(L) –– VDD × 0.3 V Logic Voltage High V I(H) VDD × 0.7 –– V Strobe Output Voltage V ST Inactive – V DD –V Active, IO = 100 to 500 μA VDD – 2.1 VDD – 2.0 VDD – 1.9 V Line Regulation ΔVST(ΔVDD) Active, VDD = 2.3 to 5.5 V – –60 – dB Strobe Temperature Coefficient αST VSTROBE, VDD = 2.3 to 5.5 V – 0.01 – % / °C Maximum IRED Current Setting I IRED(MAX) Current is set by selection of resistor on ISET pin – – 300 mA IRED Current I IRED RISET = 3 Ω 89 100 111 mA IRED Temperature Coefficient αIRED IIRED, VDD = 2.3 to 5.5 V – 0.40 – % / °C LED Drive Current I LED VLED = 0.5 V 0.6 1.2 1.8 mA Low-Battery Warning Threshold V DD(th) LVSET open 2.4 2.5 2.6 V Low-Battery Warning Minimum V DD(warn) VDD voltage guaranteed to operate SOUTx pins 1.8 V Common Mode Voltage V IC Photoamplifier input VDD – 1.0 – VDD – 0.3 V Smoke Comparator Reference Voltage V REF Any alarm condition, except hush mode – VDD – 1.6 –V I/O Input Impedance Z I/O(in) No alarm conditions 40 83 – k Ω I/O Output Impedance Z I/O(out) Local or test alarm – 3.9 5.7 k Ω 1Limits over the operating temperature range are based on characterization data. Characteristics are production tested at 25°C only. 2Typical values are at 25°C and are given for circuit design information only.

Photoelectric Smoke Detector with Interconnect, Timer, and Latching Alarm IndicatorA5303 4Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. Continued on the next page… AC ELECTRICAL CHARACTERISTICS1 Valid at TA = 25°C, VDD = 2.3 to 5.5 V, configured as in Typical Application Diagram (unless otherwise noted) Characteristics Symbol Test Conditions OSC Count Min. Typ. 2 Max. Unit Oscillator Period t osc 1 9.4 10.5 11.5 ms Smoke Check t smoke 210 9.6 10.75 11.9 s Low Battery Test tbattery No low-battery detected 2 18 41.3 45.9 50.5 min tbattery2 Low-battery detected 2 12 39 43 48 s Degraded Chamber Test tchamber No degraded chamber detected 2 18 41.3 45.9 50.5 min tchamber2 Degraded chamber detected 2 12 39 43 48 s LED Pulse Period tled0 No local or remote smoke, BLINK = VSS – – No LED Pulses tled1 No local or remote smoke, BLINK = VDD 2 12 39 43 48 s tled3 Local smoke 48 0.45 0.50 0.55 s tled4 Remote smoke only – – No LED Pulses tled6 Pushbutton test, induced alarm 48 0.45 0.50 0.55 s tled7 Timer mode, no alarm 2 10 9.67 10.75 11.83 s LED Pulse Width t w(led) 1 9.5 10.5 11.5 ms LED Pulse Spacing t sp(led) 3 pulses, degraded chamber 2 6 0.60 0.67 0.74 s STROBE Pulse Period tst1 No local or remote smoke 2 10 9.6 10.75 11.9 s tst2 After 1 of 3 valid samples 192 1.8 2.0 2.2 s tst3 After 2 of 3 valid samples and during local alarm 96 0.8 1.0 1.1 s tst4 Remote smoke only 768 7.2 8.0 8.9 s tst5 Chamber test, no local alarm 2 18 41.3 45.9 50.5 min tst6 Pushbutton test, induced alarm 24 225 252 278 ms STROBE Pulse Width t w(st) 1 9.5 10.5 11.5 ms IRED Pulse Period tired1 No local or remote smoke 2 10 9.6 10.75 11.9 s tired2 After 1 of 3 valid samples 192 1.8 2.0 2.2 s tired3 After 2 of 3 valid samples and during local alarm 96 0.8 1.0 1.1 s tired4 Remote smoke only 768 7.2 8.0 8.9 s tired5 Chamber test, no local alarm 2 18 41.3 45.9 50.5 min tired6 Pushbutton test, induced alarm 24 225 252 278 ms IRED Pulse Width t w(ired) 0.01 94 105 116 μs I/O to Active Delay t d(io) Local alarm – – 0 – s I/O Charge Dump Duration t dump End of local alarm or test 96 0.9 1.0 1.1 s Rising Edge on I/O to Alarm t r(io) No local alarm 9 to 13 9 × tosc 94.5 – 137 13 × tosc ms

Photoelectric Smoke Detector with Interconnect, Timer, and Latching Alarm IndicatorA5303 5Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. SOUTx Output Warning Period t soutx Low supply or degraded chamber 2 12 38.9 43 47.1 s SOUTx Output Warning Pulse Width t w(soutx) Low supply or degraded chamber 1 9.5 10.5 11.5 ms Horn Warning Pulse Period t horn Low battery or degraded chamber 2 12 38.9 43 47.1 s Horn Warning Pulse Width t w(horn) Low battery or degraded chamber 1 9.5 10.5 11.5 ms Horn Warning Pulse Spacing t sp(horn) 3 chirps, degraded chamber 2 6 0.60 0.67 0.74 s Horn On-Time t on(horn) Local, remote, or test alarm 48 450 500 550 ms Horn Off-Time toff1(horn) Local, remote, or test alarm (see Timing Diagrams section) 48 450 500 550 ms toff2(horn) Local, remote, or test alarm (see Timing Diagrams section) 144 1350 1500 1650 ms Timer Mode Duration t timer 57344 9.0 10.0 11.0 min Failed Push-Test Indication on SOUTx t FAIL After TEST input goes low 211 to 3072 211 × tosc 21.5 – 32.3 3072 × tosc s 1Limits over the operating temperature range are based on characterization data. Characteristics are production tested at 25°C only. 2Typical values are at 25°C and are given for circuit design information only. AC ELECTRICAL CHARACTERISTICS (continued)1 Valid at TA = 25°C, VDD = 2.3 to 5.5 V, configured as in Typical Application Diagram (unless otherwise noted) Characteristics Symbol Test Conditions OSC Count Min. Typ. 2 Max. Unit

Photoelectric Smoke Detector with Interconnect, Timer, and Latching Alarm IndicatorA5303 6Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. Pin and Circuit Description (In Typical Application) C1 Pin A capacitor connected to this pin determines the gain of the photoamplifier, A e , during the push-to-test mode and during the chamber monitor test. A typical capacitor value for this high- gain (supervisory) mode is 0.047 μF, but it should be selected based on the photochamber background reflections reaching the detector and the required level of sensitivity. A e = 1 + (C1 / 12), where C1 is in pF. Ae should not exceed 10,000 and thus C1 should not exceed 0.1 μF. Coupling of other signals to the C1, C2, and DETECT inputs must be minimized. C2 Pin A capacitor connected to this pin determines the gain of the photoamplifier, A e, during standby. A typical capacitor value for this low-gain mode is 4700 pF, but it should be selected based on a specific photochamber and the desired level of sensitiv- ity to smoke. A e = 1 + (C2 / 12), where C2 is in pF. Ae should not exceed 10,000 and thus C2 should not exceed 0.1 μF. This gain increases by a nominal 45% after a local alarm is detected (three consecutive detections). A resistor must be installed in series with the C2 capacitor. DETECT Pin This is the input to the photoamplifier and is connected to the cathode of the photodiode. The photodiode is operated at zero bias and should have low dark leakage current and low capaci- tance. A shunt resistor must be installed in parallel with the photodiode. STROBE Pin This output provides a strobed, regulated voltage of V DD – 2 V . The minus side of all internal and external photoamplifier cir- cuitry is referenced to this pin. VDD Pin This pin is connected to the positive supply potential, typically 3 V . LVSET Pin This pin allows the user to externally adjust the low-battery alarm threshold. To increase the threshold, a resistor can be con- nected between LVSET and VDD. To decrease the threshold, a resistor can be connected between LVSET and VSS. IRED Pin This output provides a pulsed drive current for the external IR emitter. To minimize noise impact, the IRED is not active when the visible LED output is active. ISET Pin This pin allows the user to externally set the IRED current by connecting a resistor between it and VSS. The IRED current controls the amount of light generated by the IR LED in the chamber. The IRED current, in mA, can be approximated using the following equation: I IRED (mA) = 300 / RISET (1) The chosen resistor should set a maximum of 300 mA (typically a minimum of 1Ω). I/O Pin A connection at this pin allows multiple smoke detectors to be interconnected. If any single unit detects smoke, its I/O pin is driven high, and all connected units will sound their associated alarm indicators. As an input, this pin is sampled every 4 clock cycles (nominally 43 ms) during standby, and two consecutive samples and one additional clock with I/O high are required before signaling an alarm. If the I/O line goes low at all during the 96.8 ms, the remote alarm is not enabled, providing sig- nificant immunity to I/O noise and other pulses on the I/O line which are shorter than 9 clock cycles. The LED is suppressed when an alarm is signaled from an interconnected unit, and any local-alarm condition causes this pin to be ignored as an input. An internal NMOS device acts as a charge dump to aid in applications involving a large (distributed) capacitance, and is activated at the end of a local or test alarm. This pin has an on-chip pull-down device and must be left unconnected if not used. In the application, there should be a series current-limiting resistor to other smoke alarms. SOUT0, SOUT1, SOUT2 Pins These pins provide push-pull CMOS logic outputs to control an external sound IC. The outputs indicate the state of the device as follows: Condition SOUT2 SOUT1 SOUT0 Standby L L L Local Alarm L L H Remote Alarm L H L Push-Test Passed L H H Push-Test Failed H L L Low-Battery H L H Degraded Chamber H H L

Photoelectric Smoke Detector with Interconnect, Timer, and Latching Alarm IndicatorA5303 7Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. HORN Pin The HORN pin is a logic output provided to enable an optional, external boost converter that can drive a piezoelectric (piezo) horn. Using a boost converter to drive a piezo horn allows alarms to generate high SPL levels from low supply voltages. HORN will be driven high to enable the boost converter. The output of the boost converter will be connected to the piezo horn such that the horn will sound when the converter is enabled. If a boost con- verter and horn are not used, this pin should be left open. BLINK Pin This logic input determines the LED operation while the device is in standby. If BLINK is connected to VDD the device will blink once every approximately 43 s in standby. If BLINK is connected to VSS the device will not blink in standby. If a low-battery or degraded-chamber condition exists while the device is in standby, the LED will blink as described in the Alarm Indications section, regardless of the state of the BLINK pin. The BLINK pin has no effect when the device is in local, remote, or test alarm. LED Pin This open-drain NMOS output is used to directly drive a visible LED. The LED indicates detector status as follows (with compo- nent values as in the typical application, all times nominal): Condition Pulse Occurrence Standby, BLINK = VDD Every 43.0 s Standby, BLINK = VSS No LED pulses Local Smoke Every 0.5 s Remote Alarm No pulses Test Mode Every 0.5 s Timer (Hush) Mode Every 10.8 s OSC CAP (Oscillator Capacitor) Pin A capacitor between this pin and VDD, along with a parallel resistor, forms part of a two-terminal oscillator and sets the inter- nal clock low time. With component values shown, this nominal time is 10.4 ms and essentially the oscillator period, which is also the STROBE pulse width. The internal clock low time can be calculated by: T low = 0.693 × ROSCCAP × COSCCAP (2) TRES (Timing Resistor) Pin A resistor between this pin and OSC CAP is part of the two-termi- nal oscillator and sets the internal clock high time, which is also the IRED pulse width. With component values shown, this time is nominally 105 μs. The internal clock high time can be calculated by: T high = 0.693 × RTRES × COSCCAP (3) VSS Pin This pin is connected to the negative supply potential (usually ground). HUSH Pin This input pin serves two purposes in standby mode. It serves to enable/disable entering the internal 10-minute (nominal) “hush” timer mode, and also as the reference for the smoke comparator during timer mode. Timer mode allows the user to temporarily hush alarms caused by nuisance smoke or steam (such as from cooking). When the voltage on this pin is greater than approximately 50 mV , entering timer mode is enabled, and a high-to-low transi- tion on the TEST pin resets and starts timer mode. If use of timer mode is not desired this pin must be connected to VSS, and timer mode is disabled. During timer mode the smoke comparator reference is established externally by a resistive divider (R1 and R2) between VDD and STROBE. Also, during timer mode the photoamplifier gain, A is internally reduced to about 55% that during the normal-gain mode. Thus, A e = 1 + (C2 / 22), where C2 is in pF. These two conditions allow the detector to operate with reduced sensitivity during timer mode. If the level of smoke increases such that the temporary alarm threshold is reached, a local alarm will sound. If the HUSH pin is connected directly to STROBE without using a resistor divider, then a local alarm will never occur during timer mode, regardless of the smoke level. When not in timer mode, the smoke comparator reference is set internally to approximately V DD – 1.6 V . The resistor dividers formed by the adjustable photoamp-divider and the HUSH divider (R1 + R2, if timer mode is used) should be chosen so that the load on STROBE does not exceed 500 μA. Thus, the photoamp-divider (8 kΩ in the typical application) in parallel with the HUSH divider (R1 + R2) shall be no less than 4 kΩ. TEST Pin This pin has an internal pulldown device and is used to manually invoke push-to-test mode and timer mode. Push-to-test mode is initiated by a voltage greater than approximately V DD – 0.5 V on this pin (usually the closure of a normally open push-button switch to VDD). After one oscillator cycle, the amplifier gain is

Worcester, Massachusetts 01615-0036 U.S.A. transition also resets the latching alarm indicator, if it is latched. SS, for at least one OSC CAP cycle. occurs, the initiating detector(s) will latch the event in memory. tery life, and to prevent masking future latched alarm indications. signals, which continue until the alarm condition is resolved. A local alarm always overrides a remote alarm and a push-test. Table 1. Alternate Pin Configuration During Diagnostic pin is high, supervisory gain is selected. amplifier gain by ≈45% (hysteresis). SOUT2 This pin is reconfigured as the smoke integrator output. low-battery threshold, the output turns on. OSC CAP This pin may be driven by an external clock source. and high. The external RC network may remain intact.

Photoelectric Smoke Detector with Interconnect, Timer, and Latching Alarm IndicatorA5303 9Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. local alarm, the LED blinks every 0.5 s (nominally), but during a remote alarm, the LED is disabled and does not blink. The degraded-chamber test occurs periodically (nominally every 45.9 min). During this test, the gain of the photoamplifier is switched to the high (supervisory) level, set by C1. The device expects that the photodiode will receive enough background reflections in the chamber to cause an alarm condition. If a faulty, dirty, or obstructed chamber prevents this during a test, the test period decreases to 43 s. After two consecutive failed tests, the device signals a degraded chamber condition to the sound IC. It also chirps the horn and pulses the LED three times every 43 seconds. The condition is resolved when the chamber is either cleared or cleaned, and the test period then reverts to (nominally) 45.9 min. The low-battery test also occurs periodically (also nominally every 45.9 min, but at a different time than the degraded-chamber test). During this test a resistive divider off VDD is compared to an internal band-gap reference. If V DD is below the threshold, the device signals a low battery condition to the sound IC and the test period decreases to 43 s. It also chirps the horn and pulses the LED once every 43 seconds. The condition is resolved when the battery is replaced and the test period then reverts to (nominally) 45.9 min.

Photoelectric Smoke Detector with Interconnect, Timer, and Latching Alarm IndicatorA5303 10Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. Timing Diagrams (Not to Scale) OSC CAP STROBE IRED Internal clock Standby Mode SOUTx VDD Chamber sensitivity Photo sample Chamber test Low-battery test Low-battery test Chamber test LED SOUTx Low Battery Condition Degraded Chamber Condition tosc tw(st) tw(led) tw(horn) thorn tsoutx tsmoke, tst1, tired1 tchamber, tst5, tired5 tbattery, tled0, tst5, tired5 (Low battery) (Degraded chamber) Test event HORN HORN thorn SOUT(2:0) = (HHL) SOUT(2:0) = (HLH) tsoutx tsp(horn) tw(horn) tw(soutx) tchamber2 tchamber2 tbattery2 tw(soutx) LED tled1 tw(horn) LED, BLINK = VDD tled1 tchamber these two pulses will not exist if BLINK = VSS tsp(led) tchamber tw(led) tbattery tbattery LED, BLINK = VSS (LED OFF) tbattery2 tw(ired)

Photoelectric Smoke Detector with Interconnect, Timer, and Latching Alarm IndicatorA5303 11Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. HORN Local Smoke Detection Condition ton(horn) toff1(horn)toff2(horn) I/O tst2,ired2 tst3,ired3 tst3,ired3tw(led) 3rd strobe without smoke1st strobe with smoke 3rd strobe with smoke STROBE IRED tw(st) tdump pmud egrahc O/I)TUPTUO( Remote Alarm Condition (INPUT) HORN I/O ton(horn) toff1(horn)toff2(horn) tr(io) tw(st) STROBE tst4,ired4 tled3 SOUTx SOUT(2:0) = (LLH) SOUTx SOUT(2:0) = (LHL) Chamber (smoke present) LED BLINK = VSS or VDD (LED OFF) LED BLINK = VSS or VDD

Photoelectric Smoke Detector with Interconnect, Timer, and Latching Alarm IndicatorA5303 12Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. Test Alarm Mode (passing) LED BLINK = VSS or VDD HORN I/O STROBE TEST tdump I/O charge dump ton(horn) toff1(horn)toff2(horn) tst6,ired6 (OUTPUT) tw(st) tw(led) tled6 SOUTx SOUT(2:0) = (LHH) Test Alarm Mode (failing) LED BLINK = VSS or VDD HORN I/O STROBE TEST tw(st)tw(led) SOUTx SOUT(2:0) = (HLL) tFAIL

Photoelectric Smoke Detector with Interconnect, Timer, and Latching Alarm IndicatorA5303 13Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. Package LE, 20-Pin TSSOP A

1.20 MAX

0.15 0.00 0.30 0.19 0.20 0.09 0.60 ±0.15

1.00 REF

C SEATING PLANEC0.10 20X

0.65 BSC

0.25 BSC

6.50±0.10 GAUGE PLANE SEATING PLANE A Terminal #1 mark area For Reference Only; not for tooling use (reference MO-153 AC) Dimensions in millimeters Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown 0.45 1.70 Reference land pattern layout (reference IPC7351 SOP65P640X110-21M); All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary to meet application process requirements and PCB layout tolerances; when mounting on a multilayer PCB, thermal vias at the exposed thermal pad land can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5) PCB Layout Reference View B B 6.10 0.65

Photoelectric Smoke Detector with Interconnect, Timer, and Latching Alarm IndicatorA5303 14Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. For the latest version of this document, visit our website: www.allegromicro.com Allegro MicroSystems offers an industry-leading range of ionization and photoelectric smoke detector ICs. For a current listing, please visit our website at: www.allegromicro.com Copyright ©2001-2010, Allegro MicroSystems, Inc. The products described herein are manufactured under one or more of the following U.S. patents: 5,045,920; 5,264,783; 5,442,283; 5,389,889; 5,581,179; 5,517,112; 5,619,137; 5,621,319; 5,650,719; 5,686,894; 5,694,038; 5,729,130; 5,917,320; and other patents pending. 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 per- mit 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’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system. 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.