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data sheet 27621.41 the a3250x and a3251x programmable switches provide tooth/ valley recognition in large gear-tooth sensing, high-temperature appli- cations. each sensor consists of a single element, chopper-stabilized hall-effect ic that can be programmed to the desired magnetic switch point, optimizing sensor airgap and timing accuracy performance after final packaging. the small package can be easily assembled and used in conjunction with a wide variety of gear/target shapes and sizes. the a3250x output turns on in the presence of a sufficiently large south- pole magnetic field while the a3251x turns off with a sufficiently large south-pole magnetic field. the sensing technology used for these sensors is hall-effect based. the sensor incorporates a single-element hall ic that switches in response to magnetic signals created by a ferrous target. the program- mability of the circuit eliminates magnet and system offsets such as those caused by tilt yet provides zero-speed detection capabilities without the associated running jitter inherent in classical digital solu- tions. a proprietary dynamic offset cancelation technique, with an internal high-frequency clock, minimizes the residual offset voltage, which is normally caused by device overmolding, temperature dependancies, and thermal stress. this technique produces devices that have an extremely stable quiescent output voltage, are immune to mechanical stress, and have precise recoverability after temperature cycling. many problems normally associated with low-level analog signals are minimized by having the hall element and amplifier in a single chip. output precision is obtained by internal gain adjustments during the manufacturing process and operate-point programming in the user? application. these sensor systems are ideal for use in gathering speed, position, and timing information using gear-tooth-based configurations. they are particularly suited to those applications that require accurate duty cycle control or accurate edge detection. the lower vibration sensitivity also 3250 dwg. ph-003-2 1 supply v cc ground 3 2 output x ptct always order by complete part number: the prefix 'a' + the basic four-digit part number + a suffix to indicate operating temperature range + a suffix to indicate package style, e.g., a3250llt . preliminary information (subject to change without notice) march 20, 2000 absolute maximum ratings supply voltage, v cc ........................ 26.5 v* reverse supply voltage, v rcc ............ -18 v output off voltage, v out ..................... v cc output current, i out ..... internally limited over-voltage supply current, i cc ... 100 ma magnetic flux density, b ............ unlimited operating temperature range, t a suffix ? .................... -40 c to +85 c suffix ? .................. -40 c to +150 c storage temperature range, t s ................................ -65 c to +170 c *fault conditions that produce supply voltage transients will be clamped by an internal zener diode. these conditions can be tolerated but should be avoided. programmable, chopper- stabilized, hall-effect switch continued next page
115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 3250 programmable, chopper- stabilized, precision, hall-effect switch 2 copyright ?2000, allegro microsystems, inc. functional block diagram makes these devices extremely useful for transmission speed sensing. the first character of the part number suffix deter- mines the device operating temperature range. suffix ? is for the automotive and industrial temperature range of -40 c to +85 c. suffix ? is for the auto- motive and military temperature range of -40 c to +150 c. two package styles provide a magnetically optimized package for most applications. suffix lt is a miniature sot-89/to-243aa transistor package for surface-mount applications; while suffix ua?is a three-lead ultra-mini-sip for through-hole mounting. features and benefits chopper stabilized for extremely low switch-point drift and immunity to mechanical stress externally programmed switch point on-chip supply-transient protection output short-circuit protection reverse battery protection wide operating voltage range defined power-on state dwg. fh-020-3 ground output <1 ? supply dynamic offset cancellation current limit reg. low-pass filter sample & hold program logic offset adjust 1 3 2 power-up control x
3250 programmable, chopper- stabilized, precision, hall-effect switch www.allegromicro.com 3 electrical characteristics over operating voltage and temperature range (unless otherwise noted). limits characteristic symbol test conditions min. typ. max. units supply voltage v cc operating 4.25 26.5 v power-on state pos after programming, v cc = 0 5 v: a3250x, b < b op high high high a3251x, b < b rp low low low low output voltage v out(sat) output on, i out = 20 ma 175 400 mv output current limit i outm output on, v out = 12 v 658095 ma output leakage current i off output off, v out = 24 v 10 a supply current i cc before programming, output off 3.0 7.0 ma before programming, output on 4.0 8.0 ma reverse supply current i rcc v rcc = -30 v -5.0 ma power-on delay t on v cc > 5 v 20 50 s output rise time t r r l = 820 ? , c l = 20 pf 200 ns output fall time t f r l = 820 ? , c l = 20 pf 100 ns clock frequency f c 340 khz zener voltage v z i zt = 100 a, t a = 25 c 273237 v zener impedance z z i zt = 10 ma, t a = 25 c50 ? note: typical data is at v cc = 5 v and t a = +25 c and is for design information only. limits characteristic symbol test conditions min. typ. max. units a3250x operate point b xp programmable offset range 500 670 850 g (output turns on), b op initial (before programming) 20 g a3251x release point resolution 10 g (output turns off), b rp ? b xp after programming, b xp 500 g -35 +35 g hysteresis b hys after programming, |b op b rp | 5.0 35 g note: typical data is at v cc = 5 v and t a = +25 c and is for design information only. magnetic characteristics over operating supply voltage and temperature range.
115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 3250 programmable, chopper- stabilized, precision, hall-effect switch 4 typical electrical characteristics 0 25 50 75 100 ambient temperature in c -50 dwg. gh-053-2 125 -25 supply current in ma 5.0 4.0 3.0 2.0 1.0 150 b < b rp b > b op v = 5 v cc 10 15 20 25 supply voltage in volts 0 dwg. gh-041-2 5 supply current in ma 0 2.0 4.0 6.0 8.0 10 b > b op b < b rp t = +25 c a 0 25 50 75 100 300 0 ambient temperature in c 200 100 -50 dwg. gh-040-4 saturation voltage in mv 150 -25 125 i = 20 ma v = 4.5?4 v out cc
3250 programmable, chopper- stabilized, precision, hall-effect switch www.allegromicro.com 5 functional description dwg. eh-012 reg sample & hold x chopper-stabilized technique. these devices use a proprietary dynamic offset cancellation 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. this technique produces devices that have an extremely stable quiescent hall output voltage, are immune to thermal stress, and have precise recoverability after temperature cycling. this technique will also slightly degrade the device output repeatabil- ity. 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. the chopper- stabilizing technique cancels the mismatching of the resistors by changing the direction of the current flowing through the hall plate and hall voltage measurement taps, while maintaining the hall-voltage signal that is induced by the external magnetic flux. the signal is, then, captured by a sample-and-hold circuit. operation. the output of the a3250x switches low (turns on) when a magnetic field (south pole) perpendicular to the hall sensor exceeds the operate point threshold (b op ). after turn-on, the output is capable of sinking 20 ma and the output voltage is v out(sat) . the a3250x operate point is programmable (see next section). when the magnetic field is reduced below the release point (b rp ), the device output goes high (turns off). +v hall voltage b + dwg. ah-011-2 +b 0 output voltage flux density dwg. gh-007-2 0 rp b v out(sat) cc v op b +v a3250x output characteristic
115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 3250 programmable, chopper- stabilized, precision, hall-effect switch 6 supply output dwg. eh-013 0.1 f supply 1 v cc 3 2 x ptct functional description (contd) the output of the a3251x switches high (turns off) when a magnetic field (south pole) perpendicular to the hall sensor exceeds the release point threshold (b rp ). the a3251x release point is programmable (see next section). when the magnetic field is reduced below the operate point (b op ), the device output goes low (turns on). after turn-on, the output is capable of sinking 20 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 hysteresis 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 chopper-stabiliza- tion technique. the simplest form of magnet that will operate these devices is a bar magnet with the south-seeking pole towards the branded surface of the device. many other methods of operation are possible. extensive applications information on magnets and hall-effect sensors is also available in the allegro electronic data book ams-702 or application note 27701, or www.allegromicro.com +b 0 output voltage flux density dwg. gh-007-5 0 cc v rp b op b v out(sat) +v a3251x output characteristic
3250 programmable, chopper- stabilized, precision, hall-effect switch www.allegromicro.com 7 programming protocol the a3250x operate point and a3251x release point are programmed by serially addressing the device through the supply terminal (pin1). after the correct operate/release point is determined, the device programming bits are selected and then a ?ock?set to prevent any further (accidental) programming. program enable. to program the device, a sequence of pulses is used to activate/enable the addressing mode as shown in figure 1. this sequence of a v pp pulse, at least seven v ph pulses, and a v pp pulse with no supply interrup- tions, is designed to prevent the device from being pro- grammed accidentally (for example, as a result of noise on the supply line). v pp v ph v pl 0 t d(1) t d(0) dwg. wh-013 program enable (at least 7 pulses) t d(1) figure 1 program enable programming protocol over operating temperature range. limits characteristic symbol description min. typ. max. units programming voltage v pl minimum voltage during programming 4.5 5.0 5.5 v v ph 9.0 10 11 v v pp 20 23 25 v programming current i pp max. supply current during programming 250 ma pulse width t d(0) off time between bits 20 s t d(1) enable, address, program, or lock bit on time 20 s t dp program pulse on time 100 300 s pulse rise time t r v pl to v ph or v pp 11 s pulse fall time t f v ph or v pp to v pl 5.0 s note: typical data is at t a = +25 c and is for design information only.
115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 3250 programmable, chopper- stabilized, precision, hall-effect switch 8 * in application, the terms ?ear?and ?arget?are often interchanged. however, ?ear?is preferred when motion is transferred. address determination. the operate point is adjust- able in 64 increments. with the appropriate target or gear* in position, the 64 switch points are sequentially selected (figure 2) until the required operate point is reached. note that the difference between the operate point and the release point (hysteresis) is a constant for all addresses. set-point programming. after the desired set-point address is determined (0 through 63), each bit of the equivalent binary address is programmed individually. for example, as illustrated in figure 3, to program address code 5 (binary 000101), bits 1 and 3 need to be programmed. each bit is programmed during the wide v pp pulse and is not reversible. lock programming. after the desired set point is programmed, the program lock is then activated (figure 4) to prevent further programming of the device. v ph v pl 0 t d(1) t d(0) dwg. wh-014 address 0 address 1 address 2 address n (up to 63) address n-1 address n-2 figure 2 address determination figure 4 lock programming v pp v ph v pl 0 t d(1) t d(0) dwg. wh-016 t dp program enable lock program (65 pulses) t d(1) figure 3 set-point programming v pp v ph v pl 0 t d(1) t d(0) dwg. wh-015 program enable bit 1 program bit 3 program (000100) address 4 t dp program enable t d(1)
3250 programmable, chopper- stabilized, precision, hall-effect switch www.allegromicro.com 9 all allegro sensors are subjected to stringent qualification requirements prior to being released to production. to become qualified, except for the destructive esd tests, no failures are permitted. criteria for device qualification qualification test test method and test conditions test length samples comments biased humidity (hast) t a = 130 c, rh = 85% 50 hrs 77 v cc = v out = 5 v high-temperature jesd22-a108, 408 hrs 77 v cc = 24 v, operating life (htol) t a = 150 c, t j = 165 cv out = 20 v accelerated htol jesd22-a108, 504 hrs 77 v cc = 24 v, t a = 175 c, t j = 190 cv out = 20 v autoclave, unbiased jesd22-a102, condition c, 96 hrs 77 t a = 121 c, 15 psig high-temperature mil-std-883, method 1008, 1000 hrs 77 (bake) storage life t a = 170 c temperature cycle mil-std-883, method 1010, 500 cycles 77 -65 c to +150 c latch-up pre/post 6 reading electro-thermally pre/post 6 induced gate leakage reading esd, cdf-aec-q100-002 pre/post x per test to failure, human body model reading test all leads > tbd electrical distributions per specification 30
115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 3250 programmable, chopper- stabilized, precision, hall-effect switch 10 sensor locations ( 0.005 [0.13 mm] die placement) package designators ua and "ua-tl" although sensor location is accurate to three sigma for a particular design, product improvements may result in small changes to sensor location. 0.045" 1.14 mm 1 3 2 dwg. mh-008-8a 0.0305" 0.775 mm nom active area depth 0.088" 2.24 mm a 1 3 2 dwg. mh-011-9b 0.0195" 0.50 mm nom branded surface active area depth 0.080" 2.04 mm 0.056" 1.44 mm a package designator lt 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 departures from the detail specifications as may be required to permit 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. allegro products are not authorized for use as critical components in life-support appliances, devices, or systems without express written approval. the information included herein is believed to be accurate and reliable. however, allegro microsystems, inc. assumes no responsibil- ity for its use; nor for any infringements of patents or other rights of third parties that may result from its use. allegro
3250 programmable, chopper- stabilized, precision, hall-effect switch www.allegromicro.com 11 dwg. ma-009-3a in 1 23 0.072 0.064 0.167 0.155 0.059 bsc 0.0189 0.0142 0.047 0.035 0.102 0.090 0.063 0.055 0.0173 0.0138 0.090 0.084 0.0221 0.0173 0.118 bsc 0.181 0.173 dwg. ma-009-3a mm 1 23 4.60 4.40 1.83 1.62 4.25 3.94 1.50 bsc 0.48 0.36 1.20 0.89 2.60 2.29 1.60 1.40 0.44 0.35 2.29 2.13 0.56 0.44 3.00 bsc package designator 'lt' (sot-89/to-243aa) dimensions in inches (for reference only) dimensions in millimeters (controlling dimensions) 13 b 2.5 0.8 2.6 1.2 4.6 2.0 dwg. ma-012-3 mm pads 1, 2, 3, and a standard sot-89 layout pads 1, 2, 3, and b low-stress version pads 1, 2, and 3 only lowest stress, but not self aligning 2 0.7 typ 0.8 typ a note: exact body and lead configuration at vendor? option within limits shown. 1 b 0.098 0.031 0.102 0.047 0.181 0.079 dwg. ma-012-3 in ds 1, 2, 3, and a standard sot-89 layout ds 1, 2, 3, and b low-stress version ds 1, 2, and 3 only lowest stress, but not self aligning 2 0.028 typ 0.031 typ a 3
115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 3250 programmable, chopper- stabilized, precision, hall-effect switch 12 surface-mount lead form (suffix '-tl') dimensions in inches (controlling dimensions) dimensions in millimeters (for reference only) package designator 'ua' 0.095 0.005 0.020 min flat dwg. mh-015 in 0.004 max 0.002 max 0 8 2.41 0.13 0.51 min flat dwg. mh-015 mm 0.10 max 0.051 max 0 8 dwg. mh-014e mm 4.17 4.04 1.57 1.47 0.44 0.35 1.27 bsc 45 16.26 15.24 0.48 0.36 2.16 max 45 0.79 123 3.10 2.97 see note dwg. mh-014e in 0.164 0.159 0.062 0.058 0.0173 0.0138 0.050 bsc 45 0.640 0.600 0.0189 0.0142 0.085 max 45 0.031 123 0.122 0.117 see note notes: 1. tolerances on package height and width represent allowable mold offsets. dimensions given are measured at the widest po int (parting line). 2. exact body and lead configuration at vendor? option within limits shown. 3. height does not include mold gate flash. 4. recommended minimum pwb hole diameter to clear transition area is 0.035?(0.89 mm). 5. where no tolerance is specified, dimension is nominal.

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