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a1147 and a1148 a1147-ds, rev. 4 worcester, massachusetts 01615-0036 (508) 853-5000 115 northeast cutoff, box 15036 www.allegromicro.com allegro microsystems, inc. ab so lute max i mum rat ings supply voltage, v cc .......................................... 28 v reverse-supply voltage, v rcc ........................ ?18 v magnetic flux density, b ......................... unlimited power dissipation, p d ............................ graph, p. 5 operating temperature ambient, t a , range e.................. ?40oc to 85oc ambient, t a , range l................ ?40oc to 150oc maximum junction, t j(max) ........................ 165oc storage temperature, t s .................. ?65oc to 170oc on-chip protection supply transient protection reverse-battery protection on-board voltage regulator 3.5 to 24 v operation low current ultrasensitive two-wire chopper-stabilized unipolar hall effect switches package lh, 3-pin sot features and benefits the a1147 and a1148 devices are two-wire, unipolar, hall effect switches that are factory-programmed at end-of-line to optimize ultrasensitive magnetic switchpoint accuracy. these devices use a patented high frequency chopper-stabilization tech- nique, produced using the allegro advanced bicmos wafer fabrication process, to achieve magnetic stability and to eliminate offset inherent in single-element devices exposed to harsh application environments. commonly found in a number of automotive applications, these switches are utilized to sense seat track position, seat belt buckle presence, hood/trunk latch- ing, and shift selector position. two-wire unipolar switches, such as the a1147 and a1148, are particularly advantageous in price-sensitive applications because they require one less wire for operation than do switches with the more traditional open-collector output. additionally, the system designer inherently gains diagnos- tics because there is always output current flowing, which should be in either of two narrow ranges. any current level not within these ranges indicates a fault con- dition. these devices also feature on-chip transient protection and a zener clamp to protect against overvoltage conditions on the supply line. the output currents of the a1148 switches high in the presence of a south (+) polarity magnetic field of sufficient strength, and switches low otherwise, as in the presence of a weak field or a north (?) polarity field. the a1147 has an oppo- site output: the currents switch low in the presence of a south-polarity magnetic field of sufficient strength, and switch high otherwise. both versions are offered in two package styles. the lh is a sot-23w, miniature low-profile package for surface-mount applications. the ua is a three-lead ultra- mini sip for through-hole mounting. each package is available in a lead (pb) free version (suffix, ?t ) with 100% matte tin plated leadframe. field-programmable versions also available: a1180 and a1181. package ua, 3-pin sip chopper stabilization low switchpoint drift over operating temperature range low sensitivity to stress factory programmed at end-of-line for optimized switchpoints 1:1 1:1
2 a1147-ds, rev. 4 worcester, massachusetts 01615-0036 (508) 853-5000 115 northeast cutoff, box 15036 www.allegromicro.com allegro microsystems, inc. low current ultrasensitive two-wire chopper-stabilized unipolar hall effect switches a1147 and a1148 nc 1 2 3 functional block diagram amp regulator low-pass filter gnd vcc gnd package ua only 0.01 uf v+ clock/logic dynamic offset cancellation sample and hold to all subcircuits 1. vcc 2. no connection 3. gnd 1 2 3 1. vcc 2. gnd 3. gnd package lh, 3-pin sot package ua, 3-pin sip
3 a1147-ds, rev. 4 worcester, massachusetts 01615-0036 (508) 853-5000 115 northeast cutoff, box 15036 www.allegromicro.com allegro microsystems, inc. low current ultrasensitive two-wire chopper-stabilized unipolar hall effect switches a1147 and a1148 electrical characteristics over the operating voltage and temperature ranges, unless otherwise specified characteristic symbol test conditions min. typ. max. units supply voltage 1 v cc 3.5 ? 24 v supply current 2 i ccl b > b op for a1147 2 ? 5 ma i cch b > b op for a1148 12 ? 17 ma reverse supply current i rcc v rcc = ?18 v ? ? ?1.6 ma supply zener clamp voltage v zsupply i cc = i ccl(max) + 3 ma; t a = 25c 28 ? 40 v supply zener clamp current 3 i zsupply v zsupply = 28 v ? ? 10 ma output slew rate 4 di/dt capacitance of the oscilloscope performing the measurement = 20 pf ? 36 ? ma/s chopping frequency f c ? 200 ? khz power-on time 5 t on c bypass = 0.01 f ? ? 25 s power-on state 6,7 pos t < t on ; v cc slew rate > 25 mv/s ? high ? ? 1 v cc represents the generated voltage between the vcc pin and the gnd pin. 2 relative values of b use the algebraic convention, where positive values indicate south magnetic polarity, and negative values indicate north magnetic polarity; therefore greater b values indicate a stronger south polarity field (or a weaker north polarity field, if present). 3 i zsupply(max) = i ccl(max) + 3 ma. 4 measured without bypass capacitor between vcc and gnd. use of a bypass capacitor results in slower current change. 5 measured with and without bypass capacitor of 0.01 f. adding a larger bypass capacitor causes longer power-on time. 6 pos is defined as true only with a v cc slew rate of 25 mv / s or greater. operation with a v cc slew rate less than 25 mv / s can permanently harm device performance. 7 pos is undefined for t > t on or b rp < b < b op . magnetic characteristics over the operating voltage and temperature ranges, unless otherwise specified characteristic symbol test conditions min. typ.* max. units operate point b op a1147 i cc = i ccl 20 37 80 g a1148 i cc = i cch release point b rp a1147 i cc = i cch 10 22 60 g a1148 i cc = i ccl hysteresis b hys b hys = b op ? b rp 51530g *typical data taken at t a = 25
4 a1147-ds, rev. 4 worcester, massachusetts 01615-0036 (508) 853-5000 115 northeast cutoff, box 15036 www.allegromicro.com allegro microsystems, inc. low current ultrasensitive two-wire chopper-stabilized unipolar hall effect switches a1147 and a1148 characteristic data supply current (high) versus ambient temperature at various levels of v cc (a1147 and a1148) supply current (low) versus ambient temperature at various levels of v cc (a1147 and a1148) ambient temperature, t a (c) ambient temperature, t a (c) v cc 3.5 v 12.0 v 24.0 v v cc 3.5 v 12.0 v 24.0 v i ccl (ma) i cch (ma) 0 2 6 8 10 4 ?50 0 50 100 150 200 ?50 0 50 100 150 200 ?50 0 50 100 150 200 switchpoint hysteresis versus ambient temperature at various levels of v cc (a1147 and a1148) operate point versus ambient temperature at various levels of v cc (a1147 and a1148) ambient temperature, t a (c) ambient temperature, t a (c) v cc 3.5 v 12.0 v 24.0 v v cc 3.5 v 12.0 v 24.0 v b op (g) b hys (g) 0 10 20 30 50 60 70 40 10 12 16 18 20 14 ?50 0 50 100 150 200 5 0 10 15 25 30 40 35 20
5 a1147-ds, rev. 4 worcester, massachusetts 01615-0036 (508) 853-5000 115 northeast cutoff, box 15036 www.allegromicro.com allegro microsystems, inc. low current ultrasensitive two-wire chopper-stabilized unipolar hall effect switches a1147 and a1148 thermal characteristics may require derating at maximum conditions, see application information characteristic symbol test conditions value units package thermal resistance r ja package lh, minimum-k pcb (single layer, single-sided with copper limited to solder pads) 110 oc/w package lh, low-k pcb (single layer, double-sided with 0.926 in 2 copper area) 228 oc/w package ua, minimum-k pcb (single layer, single-sided with copper limited to solder pads) 165 oc/w 6 7 8 9 2 3 4 5 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 20 40 60 80 100 120 140 160 180 maximum allowable v cc (v) t j(max) = 165oc; i cc =i cc(max) power derating curve (r ja = 228 oc/w) minimum-k pcb, package lh (r ja = 110 oc/w) low-k pcb, package lh (r ja = 165 oc/w) minimum-k pcb, package ua v cc(min) v cc(max) 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 20 40 60 80 100 120 140 160 180 temperature (c) power dissipation, p d (m w) power dissipation versus ambient temperature (r ja =165 o c /w) minimum-k p cb, pac kag eua ( r ja =228 oc/ w ) mini m u m- k pcb, packa ge lh (r ja = 110 oc/w) low-k pcb, package lh
6 a1147-ds, rev. 4 worcester, massachusetts 01615-0036 (508) 853-5000 115 northeast cutoff, box 15036 www.allegromicro.com allegro microsystems, inc. low current ultrasensitive two-wire chopper-stabilized unipolar hall effect switches a1147 and a1148 functional description b op b rp b hys i cc(h) i cc i cc(l) switch to low switch to high b+ bC i+ 0 () b op b rp b hys i cc(h) i cc i cc(l) switch to high switch to low b+ i+ bC 0 (b) operation the output, i cc , of the a1147 device switches low after the mag- netic field at the hall sensor exceeds the operate point threshold, b op . when the magnetic field is reduced to below the release point threshold, b rp , the device output goes high. the differ- ences between the magnetic operate and release point is called the hysteresis of the device, b hys . this built-in hysteresis allows clean switching of the output even in the presence of external mechanical vibration and electrical noise. the a1148 device switches with opposite polarity for similar b op and b rp values, in comparison to the a1147 (see figure 1). figure 1. alternative switching behaviors are available in the a114x device family. on the horizontal axis, the b+ direction in dicates increasing south polarity magnetic field strength, and the b? direction indicates decreasing south polarity field strength (inc luding the case of increasing north polarity).
7 a1147-ds, rev. 4 worcester, massachusetts 01615-0036 (508) 853-5000 115 northeast cutoff, box 15036 www.allegromicro.com allegro microsystems, inc. low current ultrasensitive two-wire chopper-stabilized unipolar hall effect switches a1147 and a1148 chopper stabilization technique when using hall-effect technology, a limiting factor for switchpoint accuracy is the small signal voltage developed across the hall element. this voltage is disproportionally small relative to the offset that can be produced at the output of the hall sensor. this makes it difficult to process the signal while maintaining an accurate, reliable output over the specified oper- ating temperature and voltage ranges. chopper stabilization is a unique approach used to minimize hall offset on the chip. the patented allegro technique, namely dynamic quadrature offset cancellation, removes key sources of the output drift induced by thermal and mechanical stresses. this offset reduction technique is based on a signal modulation- demodulation process. the undesired offset signal is separated from the magnetic field-induced signal in the frequency domain, through modulation. the subsequent demodulation acts as a modulation process for the offset, causing the magnetic field- induced signal to recover its original spectrum at baseband, while the dc offset becomes a high-frequency signal. the magnetic- sourced signal then can pass through a low-pass filter, while the modulated dc offset is suppressed. this configuration is illus- trated in figure 2. the chopper stabilization technique uses a 200 khz high frequency clock. for demodulation process, a sample and hold technique is used, where the sampling is performed at twice the chopper frequency (400 khz). this high-frequency operation allows a greater sampling rate, which results in higher accuracy and faster signal-processing capability . this approach desensi- tizes the chip to the effects of thermal and mechanical stresses, and produces devices that have extremely stable quiescent hall output voltages and precise recoverability after temperature cycling. this technique is made possible through the use of a bicmos process, which allows the use of low-offset, low-noise amplifiers in combination with high-density logic integration and sample-and-hold circuits. the repeatability of magnetic field-induced switching is affected slightly by a chopper technique. however, the allegro high- frequency chopping approach minimizes the affect of jitter and makes it imperceptible in most applications. applications that are more likely to be sensitive to such degradation are those requiring precise sensing of alternating magnetic fields; for example, speed sensing of ring-magnet targets. for such applica- tions, allegro recommends its digital sensor families with lower sensitivity to jitter. for more information on those devices, contact your allegro sales representative. figure 2. chopper stabilization circuit (dynamic quadrature offset cancellation) amp regulator clock/logic hall element sample and hold low-pass filter
8 a1147-ds, rev. 4 worcester, massachusetts 01615-0036 (508) 853-5000 115 northeast cutoff, box 15036 www.allegromicro.com allegro microsystems, inc. low current ultrasensitive two-wire chopper-stabilized unipolar hall effect switches a1147 and a1148 application information for additional general application information, visit the allegro web site at www. allegromicro.com. gnd a114x vcc v+ 0.01 f a b b gnd ecu package ua only a b maximum separation 5 mm r sense c byp figure 3. typical application circuit typical application circuit the a114x family of devices must be protected by an external bypass capacitor, c byp , connected between the supply, vcc, and the ground, gnd, of the device. c byp reduces both external noise and the noise generated by the chopper-stabilization func- tion. as shown in figure 3, a 0.01 f capacitor is typical. installation of c byp must ensure that the traces that connect it to the a114x pins are no greater than 5 mm in length. all high-frequency interferences conducted along the supply lines are passed directly to the load through c byp , and it serves only to protect the a114x internal circuitry. as a result, the load ecu (electronic control unit) must have sufficient protection, other than c byp , installed in parallel with the a114x. a series resistor on the supply side, rs (not shown), in combina- tion with c byp , creates a filter for emi pulses. when determining the minimum v cc requirement of the a114x device, the voltage drops across r s and the ecu sense resistor, r sense , must be taken into consideration. the typical value for r sense is approximately 100 ? .
9 a1147-ds, rev. 4 worcester, massachusetts 01615-0036 (508) 853-5000 115 northeast cutoff, box 15036 www.allegromicro.com allegro microsystems, inc. low current ultrasensitive two-wire chopper-stabilized unipolar hall effect switches a1147 and a1148 power derating the device must be operated below the maximum junction temperature of the device, t j(max) . under certain combinations of peak conditions, reliable operation may require derating sup- plied power or improving the heat dissipation properties of the application. this section presents a procedure for correlating factors affecting operating t j . (thermal data is also available on the allegro microsystems web site.) the package thermal resistance, r ja , is a figure of merit sum- marizing the ability of the application and the device to dissipate heat from the junction (die), through all paths to the ambient air. its primary component is the effective thermal conductivity, k, of the printed circuit board, including adjacent devices and traces. radiation from the die through the device case, r jc , is relatively small component of r ja . ambient air temperature, t a , and air motion are significant external factors, damped by overmolding. the effect of varying power levels (power dissipation, p d ), can be estimated. the following formulas represent the fundamental relationships used to estimate t j , at p d . p d = v in i in (1) ? t = p d r ja (2) t j = t a + ? t (3) for example, given common conditions such as: t a = 25c, v cc = 12 v, i cc = 4 ma, and r ja = 140 c/w, then: p d = v cc i cc = 12 v 4 ma = 48 mw ? t = p d r ja = 48 mw 140 c/w = 7c t j = t a + ? t = 25c + 7c = 32c a worst-case estimate, p d(max) , represents the maximum allow- able power level (v cc(max) , i cc(max) ), without exceeding t j(max) , at a selected r ja and t a . example : reliability for v cc at t a = 150c, package ua, using minimum-k pcb. observe the worst-case ratings for the device, specifically: r ja = 165c/w, t j(max) = 165c, v cc(max) = 24 v, and i cc(max) = 17 ma. calculate the maximum allowable power level, p d(max) . first, invert equation 3: ? t max = t j(max) ? t a = 165 c ? 150 c = 15 c this provides the allowable increase to t j resulting from internal power dissipation. then, invert equation 2: p d(max) = ? t max r ja = 15c 165 c/w = 91 mw finally, invert equation 1 with respect to voltage: v cc(est) = p d(max) i cc(max) = 91 mw 17 ma = 5 v the result indicates that, at t a , the application and device can dissipate adequate amounts of heat at voltages v cc(est) . compare v cc(est) to v cc(max) . if v cc(est) v cc(max) , then reli- able operation between v cc(est) and v cc(max) requires enhanced r ja . if v cc(est) v cc(max) , then operation between v cc(est) and v cc(max) is reliable under these conditions.
10 a1147-ds, rev. 4 worcester, massachusetts 01615-0036 (508) 853-5000 115 northeast cutoff, box 15036 www.allegromicro.com allegro microsystems, inc. low current ultrasensitive two-wire chopper-stabilized unipolar hall effect switches a1147 and a1148 device qualification program emc (electromagnetic compatibility) requirements test name reference specification esd ? human body model aec-q100-002 esd ? machine model aec-q100-003 conducted transients iso 7637-1 direct rf injection iso 11452-7 bulk current injection iso 11452-4 tem cell iso 11452-3 contact allegro for information. contact your local representative for emc results.
11 a1147-ds, rev. 4 worcester, massachusetts 01615-0036 (508) 853-5000 115 northeast cutoff, box 15036 www.allegromicro.com allegro microsystems, inc. low current ultrasensitive two-wire chopper-stabilized unipolar hall effect switches a1147 and a1148 product selection guide use the complete part numbers when ordering part number pb-free packing a package operating ambient temperature, t a (c) output level in south (+) field b a1147elhlt ? tape and reel, 3000 pieces/reel surface mount ?40 to 85 low a1147elhlt-t yes a1147eua ? bulk bag, 500 pieces/bag through hole a1147eua-t yes a1147euati ? tape and reel, 2000 pieces/reel A1147EUATI-T yes a1147llhlt ? tape and reel, 3000 pieces/reel surface mount ?40 to 150 a1147llhlt-t yes a1147lua ? bulk bag, 500 pieces/bag through hole a1147lua-t yes a1147luati ? tape and reel, 2000 pieces/reel a1147luati-t yes a1148elhlt ? tape and reel, 3000 pieces/reel surface mount ?40 to 85 high a1148elhlt-t yes a1148eua ? bulk bag, 500 pieces/bag through hole a1148eua-t yes a1148euati ? tape and reel, 2000 pieces/reel a1148euati-t yes a1148llhlt ? tape and reel, 3000 pieces/reel surface mount ?40 to 150 a1148llhlt-t yes a1148lua ? bulk bag, 500 pieces/bag through hole a1148lua-t yes a1148luati ? tape and reel, 2000 pieces/reel a1148luati-t yes a contact allegro for additional packing options. b south (+) magnetic fields must be of sufficient strength.
12 a1147-ds, rev. 4 worcester, massachusetts 01615-0036 (508) 853-5000 115 northeast cutoff, box 15036 www.allegromicro.com allegro microsystems, inc. low current ultrasensitive two-wire chopper-stabilized unipolar hall effect switches a1147 and a1148 package lh, 3-pin; (sot-23w) 2.40 bsc .094 1.00 bsc .039 0.70 bsc .028 3.10 2.90 .122 .114 2.10 1.85 .083 .073 3.00 2.70 .118 .106 0.55 ref .022 1.49 nom .059 0.28 nom .011 0.96 nom .038 0.95 bsc .037 0.95 bsc .037 0.25 min .010 0.15 0.00 .006 .000 1.13 0.87 .045 .034 0.20 0.13 .008 .005 8o 0o 0.50 .020 .012 0.30 0.25 bsc .010 gauge plane seating plane 2 1 3 dimensions in millimeters u.s. customary dimensions (in.) in brackets, for reference only a hall element b active area depth 0.28 [.011] c c fits sc?59a solder pad layout a package ua, 3-pin sip b .164 .159 4.17 4.04 .122 .117 3.10 2.97 .062 .058 1.57 1.47 .017 .014 0.44 0.35 .019 .014 0.48 0.36 .640 .600 16.26 15.24 .085 max 2.16 .050 bsc 1.27 .031 ref 0.79 .0195 nom 0.50 .0805 nom 2.04 1.44 .0565 nom 45 bsc 45 bsc dimensions in inches metric dimensions (mm) in brackets, for reference only 23 1 a a b dambar removal protrusion hall element
13 a1147-ds, rev. 4 worcester, massachusetts 01615-0036 (508) 853-5000 115 northeast cutoff, box 15036 www.allegromicro.com allegro microsystems, inc. low current ultrasensitive two-wire chopper-stabilized unipolar hall effect switches a1147 and a1148 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 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 cur- rent. allegro products are not authorized for use as critical compo- nents 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 ? 2004, 2005 allegro microsystems, inc.

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