description the a3340 hall effect switch is an extremely temperature-stable and stress-resistant sensor especially suited for operation over extended temperature ranges up to 150c. superior high-temperature performance is made possible through dynamic offset cancellation, which reduces the residual offset voltage normally caused by device overmolding, temperature dependencies, and thermal stress. the device includes on a single silicon chip a voltage regulator, hall-voltage generator, small-signal amplifier, chopper stabilization, schmitt trigger, and a short-circuit protected open-collector output to sink up to 25 ma. a south pole of sufficient strength will turn the output off. an on-board regulator permits operation with supply voltages of 4.2 to 24 volts. two package styles provide a magnetically optimized package for most applications. suffix lh is an sot23w surface mount package and while suffix ua is a three-lead ultramini sip for through hole mounting. the a3340 complements the a3240, which offers the same features, but with the opposite output polarity. a3340-ds, rev. 1 features and benefits ? resistant to physical stress ? superior temperature stability ? output short-circuit protection ? operation from unregulated supply ? reverse battery protection ? sol id-state reliability ? small size chopper-stabilized, precision hall-effect switch packages: 3 pin sot23w (suffix lh), and 3 pin sip (suffix ua) functional block diagram not to scale a3340 regulator gnd vcc vout control current limit <1 7 dynamic offset cancellation sample and hold to all subcircuits amp amp
chopper-stabilized, precision hall-effect switch a3340 2 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com selection guide part number packing* mounting ambient, t a b rp (min) b op (max) a3340elhlt-t 7-in. reel, 3000 pieces/reel 3-pin sot23w surface mount ?40oc to 85oc 550 a3340eua-t bulk, 500 pieces/bag 3-pin sip through hole a3340llhlt-t 7-in. reel, 3000 pieces/reel 3-pin sot23w surface mount ?40oc to 150oc A3340LUA-T bulk, 500 pieces/bag 3-pin sip through hole *contact allegro for additional packing options. absolute maximum ratings characteristic symbol notes rating units supply voltage v cc 26.5 v reverse supply voltage v rcc ?30 v output off voltage v out 26 v reverse output voltage v rout ?0.5 v continuous output current i out internal current limiting (intended to protect the device from output short circuits) 25 ma reverse output current i rout ?50 ma 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
chopper-stabilized, precision hall-effect switch a3340 3 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com operating characteristics , valid over t a , unless otherwise noted characteristic symbol test conditions min. typ. 1 max. units electrical characteristics supply voltage range 2 v cc operating, t j < 165c 4.2 ? 24 v output leakage current i off v out = 24 v, b > b op ??10 a output saturation voltage v out(sat) i out = 20 ma, b < b rp ? 185 500 mv output current limit i om b > b op 30 ? 60 ma power-on time t po v cc > 4.2 v ? ? 50 s chopping frequency f c ? 340 ? khz output rise time t r r load = 820 , c load = 20 pf ? 0.2 2.0 s output fall time t f r load = 820 , c load = 20 pf ? 0.1 2.0 s supply current i cc b < b rp , v cc = 12 v ? 3.0 6.0 ma b > b op , v cc = 12 v ? 4.0 6.0 ma reverse battery current i rcc v rcc = ?30 v ? ? -5.0 ma zener voltage v zd v z + v d , i cc = 15 ma, t a = 25c 28 32 37 v zener impedance z zd z z + z d , i cc = 15 ma, t a = 25c ? 50 ? magnetic characteristics 3 operate point 4 b op ?3550 g release point 4 b rp 5.0 25 ? g hysteresis b hys b op ? b rp ?6? g 1 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. 2 maximum voltage must be adjusted for power dissipation and junction temperature. 3 1 g (gauss) = 0.1 mt (millitesla). 3 b op = operate point (output turns off); b rp = release point (output turns on).
chopper-stabilized, precision hall-effect switch a3340 4 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (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 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 q ja = 228 oc/w) package lh, 1-layer pcb (r q ja = 110 oc/w) package lh, 2-layer pcb (r q ja = 165 oc/w) package ua, 1-layer pcb 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 (mw) power dissipation versus ambient temperature (r q ja = 165 o c/w ) package ua, 1-la yer pcb (r q ja = 228 oc/w) packag e lh, 1-layer pcb (r q ja = 110 o c/w) package lh, 2-layer pc b
chopper-stabilized, precision hall-effect switch a3340 5 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com typical operating characteristics as a function of temperature supply current output saturation voltage switch points 050100 ambient temperature in c -50 dwg. gh-026-5 switch points in gauss 30 operate point 150 -25 25 75 125 40 50 0 10 20 v cc = 4.5 v v cc = 24 v release point 0255075100 300 0 ambient temperature in c 200 100 -50 dwg. gh-029-4 saturation voltage in mv 150 -25 125 i out = 20 ma v cc = 12 v 6.0 supply current in ma 5.0 4.0 3.0 2.0 0255075100 ambient temperature in c -50 dwg. gh-028-5 125 -25 150 output on, b < b rp output off, b > b op v cc = 12 v
chopper-stabilized, precision hall-effect switch a3340 6 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com supply current output saturation voltage typical operating characteristics as a function of supply voltage switch points 4.0 4.5 5.0 supply voltage in volts 3.0 dwg. gh-021-2 3.5 release point switch point in gauss 40 30 20 10 0 operate point 24 t a = 150 c t a = -40 c 4.0 4.5 5.0 supply voltage in volts 3.0 dwg. gh-055-1 3.5 24 t a = 150 c t a = +25 c t a = -40 c i out = 20 ma 250 150 saturation voltage in mv 200 225 175 4.0 6.0 9.0 supply voltage in volts 3.0 dwg. gh-058-4 5.0 12 t a = 150 c t a = +25 c t a = -40 c 7.0 5.0 3.0 1.0 supply current in ma 6.0 4.0 2.0 8.0 0 output on 10 11 8.0 7.0
chopper-stabilized, precision hall-effect switch a3340 7 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com dwg. eh-012 reg x sample & hold +v cc b ? v hall +v hall +b 0 flux density 0 b cc v b +v op rp output voltage v out(sat) supply output dwg. eh-013 0.1 f supply x ptct vcc gnd vout chopper-stabilized technique. the hall element can be considered as a resistor array similar to a wheatstone bridge. a large portion of the offset is a result of the mismatching of these resistors. these devices use a proprietary dynamic offset cancel- lation technique, with an internal high-frequency clock to reduce the residual offset voltage of the hall element that is normally caused by device overmolding, temperature dependencies, and thermal stress. the chopper-stabilizing technique cancels the mismatching of the resistor circuit by changing the direction of the current flowing through the hall plate using cmos switches and hall voltage measurement taps, while maintaing the hall- voltage signal that is induced by the external magnetic flux. the signal is then captured by a sample-andhold circuit and further processed using low-offset bipolar circuitry. this technique pro- duces devices that have an extremely stable quiescent hall output voltage, are immune to thermal stress, and have precise recover- ability after temperature cycling. this technique will also slightly degrade the device output repeatability. a relatively high sampling frequency is used in order that faster signals can be processed. more detailed descriptions of the circuit operation can be found in: technical paper stp 97-10, monolithic magnetic hall sensor using dynamic quadrature offset cancellation and technical paper stp 99-1, chopper-stabilized amplifiers with a track-and- hold signal demodulator. operation . the output of these devices switches high (turns off) when a magnetic field (south pole) perpendicular to the hall sensor exceeds the operate point thresh- old (b op ). when the magnetic field is reduced below the release point (b rp ), the device output goes low (turns on). after turn-on, the output is capable of sinking 25 ma and the output voltage is v out(sat) . the difference in the magnetic operate and release points is the hysteresis (b hys ) of the device. this built-in hyster- esis allows clean switching of the output even in the presence of external mechanical vibration and electrical noise. applications. it is strongly recommended that an external bypass capacitor be connected (in close proximity to the hall sensor) between the supply and ground of the device to reduce both external noise and noise generated by the chopperstabilization technique. the simplest form of magnet that will operate these devices is a ring magnet. other methods of operation, such as linear magnets, are possible. extensive applications information on magnets and hall-effect sensors is also available in application note 27701, or at www.allegromicro.com. functional description
chopper-stabilized, precision hall-effect switch a3340 8 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com package lh, 3-pin (sot-23w) b b b 0.95 2.975 0.180 1.91 0.40 0.05 1.00 0.25 1.49 0.96 0.38 2.90 4o 10o 10o gauge plane seating plane 2 1 3 all dimensions nominal, not for tooling use dimensions in millimeters a b active area depth hall element, not to scale a 0.28 pin-out diagrams terminal list name description number package lh package ua vcc connects power supply to chip 1 1 vout output from circuit 2 3 gnd ground 3 2 package lh 1 3 2 ptct x package ua ptct 12 3 g x
chopper-stabilized, precision hall-effect switch a3340 9 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com package ua, 3-pin sip b b b .161 [4.09] .060 [1.52] .031 [0.79] .119 [3.02] .590 [14.99] .017 [0.43] .050 [1.27] .016 [0.41] .085 [2.16] max 45 45 .081 2.06 1.45 .057 b all dimensions nominal, not for tooling use dimensions in inches, metric dimensions (mm) in brackets, for reference only 23 1 a a active area depth hall element (not to scale) .0195 [0.50] copyright ?2004, 2007, 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. for the latest version of this document, visit our website: www.allegromicro.com
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