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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 s 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 (le) package (0.65 mm nominal lead pitch) and a 20-contact qfn (es) package with exposed thermal pad. both packages are lead (pb) free with 100% matte tin leadframe plating. 5303-ds, rev. 1 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 packages: not to scale a5303 typical application diagram c o n t r o l l o g i c s o u t 0 v d d t e s t c 1 5 6 n f c 2 5 . 6 n f d e t e c t g ai n s el ec t s t r o b e i r e d v dd o s c t i m i n g l o w b a t t 1 . 2 v 3 v 1 0 0 f l e d v s s 5 6 0 ? 2 0 0 k ? 1 0 f v d d - 1 . 6 v o s c c a p 1 5 0 0 p f p u sh - t o - te st h u s h c o n n e ct h u s h t o v s s t o d i sa b l e t i m e r m o d e c o n n e ct t o a l l o w ti m e r ( hu sh ) m o d e o p e r a t i o n i s e t l v s e t lo w ba tt sa m p l e a a a r e si st o r co n n e ct e d b e t w e e n t h i s p i n a n d v d d o r v s s a d j u st s t h e l o w - b a t t e r y t h r e sh o l d s o u t 1 v o i ce i c o u t p u t s 10 ? 100 k? s o u t 2 t r e s i / o 2 2 0 ? t o / f r o m o t h e r u n i t s v dd v dd v dd b l i n k i n st a n d b y , b l i n k = v d d ca u se s l e d t o b l i n k, b l i n k = v s s ca u se s l e d n o t t o b l i n k h o r n o u t p u t t o o p t i o n a l b o o st co n v e r t e r t o d r i v e a p i e z o h o r n s m o ke c h a m b e r r e d l e d b b r 1 r 2 5 k ? 3 k ? 3 ? 1 k ? 20-contact qfn 4 mm 4 mm 0.75 mm (es package) 20-pin tssop (le package)
2 selection guide part number pb-free and rohs package packing a5303sestr-t yes 20-contact qfn 1500 pieces / 7-in. reel 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 v ss C2.3 to 6 v dc input voltage range v in referenced to v ss C0.3 to 6 v operating ambient temperature range t a allegro range s C20 to 85 oc maximum junction temperature t j (max) 150 oc storage temperature range t stg C55 to 150 oc pin-out diagram thermal characteristics characteristic symbol test conditions* value units package thermal resistance r ja es package, 4-layer pcb, based on jedec standard 37 oc/w le package, estimated, single-layer pcb, minimal exposed copper area 127 oc/w *additional thermal information available on allegro website. terminal list number name function es le 14 1 sout1 logic push-pull output for controlling an external sound ic 15 2 sout0 logic push-pull output for controlling an external sound ic 16 3 i/o input-output to interconnected detectors 17 4 blink logic input for enabling/disabling the led blink during standby 18 5 hush input for photoamplifier timer mode reference; can also disable timer mode 19 6 iset a resistor on this pin connected to vss sets the ired output current 20 7 vdd positive supply voltage 1 8 ired terminal to drive smoke chamber ir led 2 9 strobe strobed supply (v dd C 2 v) for photoamplifier low-side reference 3 10 detect photoamplifier input 4 11 c2 sets photoamplifier gain in standby mode 5 12 c1 sets photoamplifier gain in supervisory mode 6 13 lvset optionally used with a resistor to adjust the low-battery threshold 7 14 tres connection for resistor to set clock times/frequency 8 15 vss negative supply voltage 9 16 osc cap connection for capacitor and resistor to set clock times/frequency 10 17 test enables push-to-test mode; starts timer mode, if enabled 11 18 horn logic output which optionally enables a boost converter to drive a horn 12 19 led output to drive visible led 13 20 sout2 logic push-pull output for controlling an external sound ic pad C C exposed pad for enhanced thermal dissipation 1 2 3 4 5 6 7 8 9 10 20 19 18 17 16 15 14 13 12 11 sout1 sout0 i/o blink hush iset vdd ired strobe detect sout2 led horn test osc cap vss tres lvset c1 c2 le package es package pad 15 14 13 12 11 1 2 3 4 5 6 7 8 9 10 20 19 18 17 16 vdd iset hush blink io lvset tres vss osc cap test sout0 sout1 sout2 led horn ired strobe detect c2 c1 photoelectric smoke detector with interconnect, timer, and latching alarm indicator a5303 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
3 dc electrical characteristics 1 valid at t a = 25c, v dd = 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 C 2.3 5.0 a during strobe on, ired off C 210 300 a during strobe on, ired on C 220 300 a input current i in blink, c1, c2, detect, osc cap, tres (pulldown off) C100 0 100 na test pulldown current i in(test) v test = v dd = 3 v C 3.5 C a logic voltage low v i(l) C C v dd 0.3 v logic voltage high v i(h) v dd 0.7 C C v strobe output voltage v st inactive C v dd C v active, i o = 100 to 500 a v dd C 2.1 v dd C 2.0 v dd C 1.9 v line regulation v st(vdd) active, v dd = 2.3 to 5.5 v C C60 C db strobe temperature coefficient st v strobe , v dd = 2.3 to 5.5 v C 0.01 C % / c maximum ired current setting i ired(max) current is set by selection of resistor on iset pin C C 300 ma ired current i ired r iset = 3 89 100 111 ma ired temperature coefficient ired i ired , v dd = 2.3 to 5.5 v C 0.40 C % / c led drive current i led v led = 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 v dd C 1.0 C v dd C 0.3 v smoke comparator reference voltage v ref any alarm condition, except hush mode C v dd C 1.6 C v i/o input impedance z i/o(in) no alarm conditions 40 83 C k i/o output impedance z i/o(out) local or test alarm C 3.9 5.7 k 1 limits over the operating temperature range are based on characterization data. characteristics are production tested at 25c only. 2 typical values are at 25c and are given for circuit design information only. photoelectric smoke detector with interconnect, timer, and latching alarm indicator a5303 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
4 continued on the next page ac electrical characteristics 1 valid at t a = 25c, v dd = 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 2 10 9.6 10.75 11.9 s low battery test t battery no low-battery detected 2 18 41.3 45.9 50.5 min t battery2 low-battery detected 2 12 39 43 48 s degraded chamber test t chamber no degraded chamber detected 2 18 41.3 45.9 50.5 min t chamber2 degraded chamber detected 2 12 39 43 48 s led pulse period t led0 no local or remote smoke, blink = vss C C no led pulses C C t led1 no local or remote smoke, blink = vdd 2 12 39 43 48 s t led3 local smoke 48 0.45 0.50 0.55 s t led4 remote smoke only C C no led pulses C C t led6 pushbutton test, induced alarm 48 0.45 0.50 0.55 s t led7 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 t st1 no local or remote smoke 2 10 9.6 10.75 11.9 s t st2 after 1 of 3 valid samples 192 1.8 2.0 2.2 s t st3 after 2 of 3 valid samples and during local alarm 96 0.8 1.0 1.1 s t st4 remote smoke only 768 7.2 8.0 8.9 s t st5 chamber test, no local alarm 2 18 41.3 45.9 50.5 min t st6 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 t ired1 no local or remote smoke 2 10 9.6 10.75 11.9 s t ired2 after 1 of 3 valid samples 192 1.8 2.0 2.2 s t ired3 after 2 of 3 valid samples and during local alarm 96 0.8 1.0 1.1 s t ired4 remote smoke only 768 7.2 8.0 8.9 s t ired5 chamber test, no local alarm 2 18 41.3 45.9 50.5 min t ired6 pushbutton test, induced alarm 24 225 252 278 ms ired pulse width t w(ired) 0.01 94 105 116 s i/o to active delay t d(io) local alarm C C 0 C 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 t osc 94.5 C 137 13 t osc ms photoelectric smoke detector with interconnect, timer, and latching alarm indicator a5303 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
5 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 t off1(horn) local, remote, or test alarm (see timing diagrams section) 48 450 500 550 ms t off2(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 2 11 to 3072 2 11 t osc 21.5 C 32.3 3072 t osc s 1 limits over the operating temperature range are based on characterization data. characteristics are production tested at 25c only. 2 typical values are at 25c and are given for circuit design information only. ac electrical characteristics (continued) 1 valid at t a = 25c, v dd = 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 indicator a5303 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
6 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 f, but it should be selected based on the photochamber background reflections reaching the detector and the required level of sensitivity. a e = 1 + (c 1 / 12), where c 1 is in pf. a e should not exceed 10,000 and thus c 1 should not exceed 0.1 f. 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 + (c 2 / 12), where c 2 is in pf. a e should not exceed 10,000 and thus c 2 should not exceed 0.1 f. 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 C 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 / r iset (1) the chosen resistor should set a maximum of 300 ma (typically a minimum of 1). 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 indicator a5303 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
7 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 r osccap c osccap (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 s. the internal clock high time can be calculated by: t high = 0.693 r tres c osccap (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 e , is internally reduced to about 55% that during the normal-gain mode. thus, a e = 1 + (c 2 / 22), where c 2 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 C 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 a. thus, the photoamp-divider (8 k in the typical application) in parallel with the hush divider (r1 + r2) shall be no less than 4 k. 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 C 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 photoelectric smoke detector with interconnect, timer, and latching alarm indicator a5303 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
8 increased by internal selection of c1 so that background reflec - tions in the smoke chamber can be used to simulate a smoke con - dition, and ired pulses every 252 ms (nominal). after the third ired pulse (three consecutive simulated smoke conditions), the successful test signals a continuous passing-test-alarm condition to the sound ic, outputs the temporal pattern to the piezo horn, and activates the i/o pin. when the pushbutton is released, the input returns to v ss due to the internal pulldown. after one oscil - lator cycle, the amplifier gain returns to normal, and after three additional ired pulses (less than one second), the device exits this mode and returns to standby. this high-to-low transition on test also resets and starts the 10-minute (nominal) hush timer mode, if the mode is enabled via the hush pin. the high-to-low transition also resets the latching alarm indicator, if it is latched. if the chamber malfunctions or is too dirty, the push-test will fail to simulate a smoke condition, and after three failed strobe pulses the device signals a continuous failing-test-alarm condi - tion on the soutx pins. the piezo driver and the i/o pins are not enabled. diagnostic test/calibration mode is available to facilitate calibra - tion and test of the ic and the assembled detector. it is initiated by pulling test below v ss by continuously drawing 200 a from the pin for at least one clock cycle on osc cap. the cur - rent should not exceed 500 a and under these conditions, test pin voltage will clamp at approximately 250 mv below v ss . one option is to connect test to a C5 v supply through a 15 k resistor. in this mode, certain device pins are reconfigured as described in table 1. the ired pulse rate is increased to one pulse every osc cap cycle and the strobe pin is always active. to exit this mode, the test pin should be floated, or returned to v ss , for at least one osc cap cycle. latching alarm indicator when multiple smoke detectors are networked through the i/o line, the latching alarm indicator allows the user to identify which detector(s) initiated an alarm. when a local alarm condition occurs, the initiating detector(s) will latch the event in memory. after the alarm condition has expired (the device stops signaling the alarm condition to the sound ic) the initiating detector(s) will output an additional 10 ms led pulse every 43 seconds. if the blink pin is connected to vdd, the additional pulse will occur 0.67 seconds after the normal standby pulse. the user can clear the latched alarm condition by pressing and releasing the push-to- test button. if the user does not press the push-to-test button, the latched alarm condition will cease after 24 hours to preserve bat - tery life, and to prevent masking future latched alarm indications. alarm indications alarm conditions include: local smoke detection, a remote alarm, low battery, and degraded chamber sensitivity. these are indi - cated by a combination of soutx output, piezo horn, and led signals, which continue until the alarm condition is resolved. a local alarm always overrides a remote alarm and a push-test. remote alarm always overrides a push-test. a local alarm, remote alarm, or a push-test will inhibit warning signals for low battery or degraded chamber. during a local or a remote alarm condition, the device continu - ously signals an alarm condition on the soutx pins that indi - cates the type of the alarm. the piezo horn output is a continuous modulated tone (temporal horn pattern), nominally: 0.5 s on, 0.5 s off, 0.5 s on, 0.5 s off, 0.5 s on, and 1.5 s off. the visible led also distinguishes a local alarm from a remote alarm. during a table 1. alternate pin configuration during diagnostic test/calibration mode pin name alternate configuration i/o disabled as an output. a logic high on this pin places the photoamplifier output on the blink pin. the amplifier output appears as pulses. hush if the i/o pin is high, this pin controls the amplifier gain capacitor. if this pin is low, normal gain is selected. if this pin is high, supervisory gain is selected. note: if i/o is low, clocking this pin will cause the device to exit diagnostic/calibration mode and enter an allegro-defined test mode. blink if the i/o pin is high, this pin is reconfigured as the photoamplifier output. sout0 if the i/o pin is high and the hush pin is low (normal gain), taking this pin to a high logic level increases the amplifier gain by 45% (hysteresis). sout2 this pin is reconfigured as the smoke integrator output. three consecutive smoke detections will cause this pin to go high and three consecutive no-smoke detections cause this pin to go low. led this pin becomes a low-battery indicator. the open- drain nmos output is normally off. if v dd falls below the low-battery threshold, the output turns on. osc cap this pin may be driven by an external clock source. driving this pin low and high drives the internal clock low and high. the external rc network may remain intact. photoelectric smoke detector with interconnect, timer, and latching alarm indicator a5303 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
9 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 indicator a5303 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
10 timing diagrams (not to scale) osc cap str o be i r e d internal c loc k standby mode soutx v dd cha mber sen s itivity photo s a mple chamb er t e s t low -batte ry tes t low -batte ry tes t chamb er t e s t led soutx low batt ery condition degraded chamber condition t o s c t w ( s t ) t w ( l ed) t w ( hor n ) t hor n t s out x t s mo k e , t s t 1 , t i r ed1 t c hamber , t st5 , t i r ed5 t batte r y , t l ed0 , t st5 , t i r ed5 (low battery ) (degraded chamber) t es t event h o r n h o r n t hor n sout (2:0) = (hhl) sout (2:0) = (hlh) t s out x t sp( hor n ) t w ( hor n ) t w ( s out x ) t c hamber 2 t c hamber 2 t b a tte r y 2 t w ( s out x ) led t l ed1 t w ( hor n ) led, b l i n k = v d d t l ed1 t c hamber these t w o pulses w ill not e x ist if blink = v s s t s p ( l ed) t c hamber t w ( l ed) t batte r y t batte r y led, b l i n k = v s s ( l ed off) t b a tte r y 2 t w ( i r ed) photoelectric smoke detector with interconnect, timer, and latching alarm indicator a5303 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
11 h o r n local smoke detection condition t o n ( hor n ) t o ff1 ( hor n ) t o ff2 ( hor n ) i/o t s t 2 , i r ed2 t s t 3 , i r ed3 t s t 3 , i r ed3 t w ( l ed) 3rd strobe w i thout smoke 1st strobe w i th smoke 3rd strobe w i th smoke strobe i r e d t w ( s t ) t dump p m u d e g r a h c o / i ) t u p t u o ( remote al arm condition (input ) h o r n i/o t on( hor n ) t o ff1 ( hor n ) t o ff2 ( hor n ) t r(io ) t w ( s t ) strobe t s t 4 , i r ed4 t l ed3 soutx sout (2:0) = (llh) soutx sout (2:0) = (lhl) chamber (smoke present) led blin k = v s s o r v d d ( l ed off) led blin k = v s s o r v d d photoelectric smoke detector with interconnect, timer, and latching alarm indicator a5303 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
12 test alarm mode (passing) led blin k = v s s o r v d d h o r n i/o strobe test t dump i/o charge dump t on( hor n ) t o ff1 ( hor n ) t o ff2 ( hor n ) t s t 6 , i r ed6 (out put ) t w ( s t ) t w ( l ed) t l ed6 soutx sout (2:0) = (lhh) t est al arm mode (failing) led blin k = v s s o r v d d h o r n i/o strobe test t w ( s t ) t w ( l ed) soutx sout (2:0) = (hll) t fai l photoelectric smoke detector with interconnect, timer, and latching alarm indicator a5303 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
13 package es, 20-contact qfn with exposed thermal pad 0.95 c seating plane c 0.08 21x 20 20 2 1 1 2 20 2 1 a a terminal #1 mark area coplanarity includes exposed thermal pad and terminals b exposed thermal pad (reference only, terminal #1 identifier appearance at supplier discretion) for reference only, not for tooling use (reference dwg-2864) dimensions in millimeters exact case and lead configuration at supplier discretion within limits shown c d d c reference land pattern layout (reference ipc7351 qfn50p400x400x80-21bm) 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) 4.10 0.30 0.50 4.10 0.50 bsc 0.75 0.05 0.25 +0.05 ?0.07 2.45 +0.10 ?0.15 2.45 +0.10 ?0.15 0.40 0.10 4.00 0.10 4.00 0.10 2.45 2.45 b pcb layout reference view photoelectric smoke detector with interconnect, timer, and latching alarm indicator a5303 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
14 package le, 20-pin tssop a 1.20 max 0.15 0.00 0.30 0.19 0.20 0.09 8o 0o 0.60 0.15 1.00 ref c sea ting plane c 0.10 20x 0.65 bsc 0.25 bsc 2 1 20 6.500.10 4.400.10 6.400.20 gauge plane sea ting 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 20 2 1 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 indicator a5303 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
15 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 ?2001-2012, allegro microsystems, inc. allegro microsystems, inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to per - mit 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. allegros products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of allegros product can reasonably be expected to cause bodily harm. 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. revision history revision revision date description of revision rev. 1 november tbd, 2012 add es package photoelectric smoke detector with interconnect, timer, and latching alarm indicator a5303 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com

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