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description the a1140, a1142, and a1143 devices are sensitive, two-wire, unipolar, hall effect switches that are factory-programmed at end-of-line to optimize magnetic switchpoint accuracy. these devices use a patented high frequency chopper-stabilization technique, 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 in sensing seat track position, seat belt buckle presence, hood/trunk latching, and shift selector position. two-wire unipolar switches, such as the a1140/a1142/a1143 family, 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 diagnostics 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 condition. the a1140/a1142/a1143 family of switches also features on-chip a1140-ds, rev. 17 features and benefits ? chopper stabilization ? low switchpoint drift over operating temperature range ? low sensitivity to stress ? factory programmed at end-of-line for optimized switchpoints ? on-chip protection ? supply transient protection ? reverse-battery protection ? on-board voltage regulator ? 3.5 to 24 v operation sensitive two-wire chopper-stabilized unipolar hall effect switches continued on the next page? functional block diagram not to scale packages: 3 pin sot23w (suffix lh), and 3 pin sip (suffix ua) a1140, a1142, and a1143 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
sensitive two-wire chopper-stabilized unipolar hall effect switches a1140, a1142, and a1143 2 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com transient protection and a zener clamp to protect against overvoltage conditions on the supply line. the output currents of the a1143 switch high in the presence of a south (+) polarity magnetic field of sufficient strength, and switch low otherwise, as in the presence of a weak field or a north (?) polarity field. the other two devices in the family (a1140 and a1142) have an opposite output: the currents switch low in the presence of a south-polarity magnetic field of sufficient strength, and switch high otherwise. the other differences in the switches are their defined low current levels and magnetic switchpoints. all 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 ultramini 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, a1182, and a1183. absolute maximum ratings characteristic symbol notes rating units supply voltage v cc 28 v reverse supply voltage v rcc ?18 v magnetic flux density b unlimited g operating ambient temperature t a range e ?40 to 85 oc range l ?40 to 150 oc maximum junction temperature t j (max) 165 oc storage temperature t stg ?65 to 170 oc description (continued) nc 1 2 3 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
sensitive two-wire chopper-stabilized unipolar hall effect switches a1140, a1142, and a1143 3 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com product selection guide part number packing 1 package operating ambient temperature, t a (c) output level in south (+) field 2 supply current at low output, i cc(l) (ma) a1140elhlt-t 3,4 tape and reel, 3000 pieces/reel surface mount ?40 to 85 low 2 to 5 a1142elhlt-t 5 tape and reel, 3000 pieces/reel surface mount ?40 to 85 low 5 to 6.9 a1142lua-t 5 bulk bag, 500 pieces/bag through hole ?40 to 150 a1143elhlt-t 5 tape and reel, 3000 pieces/reel surface mount ?40 to 85 high a1143eua-t 5 bulk bag, 500 pieces/bag through hole a1143llhlt-t 5 tape and reel, 3000 pieces/reel surface mount ?40 to 150 A1143LUA-T 5 bulk bag, 500 pieces/bag through hole 1 contact allegro for additional packing options. 2 south (+) magnetic fields must be of sufficient strength. 3 this device is available only in limited distribution. interested customers should contact the appropriate sales person or fiel d application engineer for more information on availability. 4 variant is in production but has been determined to be not for new design. this classification indicates that sale of the varia nt is cur- rently restricted to existing customer applications. the variant should not be purchased for new design applications because ob solescence in the near future is probable. samples are no longer available. status change: january 31, 2011. 5 these variants are in production, however, they have been deemed pre-end of life. the products are approaching end of life. wit hin a minimum of 6 months, the devices will enter their final, last time buy, order phase. suggested replacements: for the a1142elhlt -t use the a1152llhlx-t, for the a1143elhlt-t and the a1143llhlt-t use the a1153llhlx-t. status change: january 31, 2011. suggested replacements: for the a1142lua-t use the a1152lua-t, for the a1143eua-t and the A1143LUA-T use the a1153lua-t. status change: march 8, 2011.
sensitive two-wire chopper-stabilized unipolar hall effect switches a1140, a1142, and a1143 4 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com 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 cc(l) b>b op for a1140 2 ? 5 ma b>b op for a1142; bb op for a1143 b 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 measured without bypass capacitor between vcc and gnd. use of a bypass capacitor results in slower current change. 3 measured with and without bypass capacitor of 0.01 f. adding a larger bypass capacitor causes longer power-on time. 5 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. 6 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 a1140, a1142 i cc = i cc(l) 50 80 110 g a1143 i cc = i cc(h) release point b rp a1140, a1142 i cc = i cc(h) 45 65 105 g a1143 i cc = i cc(l) hysteresis b hys b hys = b op ? b rp 51530g *typical data are for initial design estimations only, and assume optimum manufacturing and application conditions, such as t a = 25c and v cc = 12 v. performance may vary for individual units, within the specified maximum and minimum limits.
sensitive two-wire chopper-stabilized unipolar hall effect switches a1140, a1142, and a1143 5 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com characteristic data 0 2 6 8 10 supply current (low) versus ambient temperature at various levels of v cc (a1142 and a1143) supply current (low) versus ambient temperature at various levels of v cc (a1140) 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 cc(l) (ma) i cc(l) (ma) 0 2 6 8 10 4 4 ?50 0 50 100 150 200 ?50 0 50 100 150 200 ?50 0 50 100 150 200 operate point versus ambient temperature at various levels of v cc (a1140, a1142, and a1143) supply current (high) versus ambient temperature at various levels of v cc (a1140, a1142, and a1143) 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 cc(h) (ma) b op (g) 10 12 16 18 20 14 ?50 0 50 100 150 200 switchpoint hysteresis versus ambient temperature at various levels of v cc (a1140, a1142, and a1143) ambient temperature, t a (c) v cc 3.5 v 12.0 v 24.0 v b hys (g) 0 2 6 8 10 4 ?50 0 50 100 150 200 50 60 80 90 110 100 70
sensitive two-wire chopper-stabilized unipolar hall effect switches a1140, a1142, and a1143 6 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com thermal characteristics may require derating at maximum conditions, see application information characteristic symbol test conditions* value units package thermal resistance r ja package lh, 1-layer pcb with copper limited to solder pads 228 oc/w package lh, 2-layer pcb with 0.463 in. 2 of copper area each side connected by thermal vias 110 oc/w package ua, 1-layer pcb with copper limited to solder pads 165 oc/w *additional thermal information available on allegro web site. 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 temperature (oc) maximum allowable v cc (v) power derating curve (r ja = 228 oc/w) 1-layer pcb, package lh (r ja = 110 oc/w) 2-layer pcb, package lh (r ja = 165 oc/w) 1-layer 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 oc/w) 1-layer pcb, p a ckage u a (r ja = 22 8 o c /w ) 1-layer pc b, pa cka ge lh (r j a = 110 oc/w) 2-layer pcb, packag e lh
sensitive two-wire chopper-stabilized unipolar hall effect switches a1140, a1142, and a1143 7 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com functional description b op b rp b hys i cc(h) i cc i cc(l) switch to low switch to high b+ b? i+ 0 (a) a1140, a1142 b op b rp b hys i cc(h) i cc i cc(l) switch to high switch to low b+ i+ b? 0 (b) a1143 operation the output, i cc , of the a1140 and a1142 devices switch low after the magnetic field at the hall element exceeds the oper- ate point threshold, b op . when the magnetic field is reduced to below the release point threshold, b rp , the device output goes high. the differences 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 pres- ence of external mechanical vibration and electrical noise. the a1143 device switches with opposite polarity for similar b op and b rp values, in comparison to the a1140 and a1142 (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).
sensitive two-wire chopper-stabilized unipolar hall effect switches a1140, a1142, and a1143 8 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com 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 element. 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 illustrated 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 device 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
sensitive two-wire chopper-stabilized unipolar hall effect switches a1140, a1142, and a1143 9 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com 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 .
sensitive two-wire chopper-stabilized unipolar hall effect switches a1140, a1142, and a1143 10 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com 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.
sensitive two-wire chopper-stabilized unipolar hall effect switches a1140, a1142, and a1143 11 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com 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 7637-2 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.
sensitive two-wire chopper-stabilized unipolar hall effect switches a1140, a1142, and a1143 12 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com package lh, 3-pin; (sot-23w) 0.55 ref gauge plane seating plane 0.25 bsc 0.95 bsc 0.95 1.00 0.70 2.40 2 1 a active area depth, 0.28 mm ref b c c b reference land pattern layout all pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary to meet application process requirements and pcb layout tolerances branding scale and appearance at supplier discretion a pcb layout reference view standard branding reference view 1 branded face n = last two digits of device part number t = temperature code nnt 2.90 +0.10 ?0.20 44 8x 10 ref 0.180 +0.020 ?0.053 0.05 +0.10 ?0.05 0.25 min 1.91 +0.19 ?0.06 2.98 +0.12 ?0.08 1.00 0.13 0.40 0.10 for reference only; not for tooling use (reference dwg. 802840) dimensions in millimeters dimensions exclusive of mold flash, gate burrs, and dambar protrusions exact case and lead configuration at supplier discretion within limits shown d hall element, not to scale d d d 1.49 0.96 3
sensitive two-wire chopper-stabilized unipolar hall effect switches a1140, a1142, and a1143 13 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com package ua, 3-pin sip 23 1 0.79 ref 1.27 nom 2.16 max 0.51 ref 45 c 45 b e e e 2.04 1.44 gate burr area a b c dambar removal protrusion (6x) a d e d branding scale and appearance at supplier discretion hall element, not to scale active area depth, 0.50 mm ref for reference only; not for tooling use (reference dwg-9049) dimensions in millimeters dimensions exclusive of mold flash, gate burrs, and dambar protrusions exact case and lead configuration at supplier discretion within limits shown standard branding reference view = supplier emblem n = last two digits of device part number t = temperature code nnt 1 mold ejector pin indent branded face 4.09 +0.08 ?0.05 0.41 +0.03 ?0.06 3.02 +0.08 ?0.05 0.43 +0.05 ?0.07 15.75 0.51 1.52 0.05
sensitive two-wire chopper-stabilized unipolar hall effect switches a1140, a1142, and a1143 14 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com copyright ?2004-2010, allegro microsystems, inc. 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. for the latest version of this document, visit our website: www.allegromicro.com revision history revision revision date description of revision rev. 17 march 8, 2011 change in product availability

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