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description the ats643 is an optimized combination of integrated circuit and magnet that provides a manufacturer-friendly solution for true zero-speed digital gear-tooth sensing in two-wire applications. the device consists of a single-shot molded plastic package that includes a samarium cobalt magnet, a pole piece, and a hall-effect ic that has been optimized to the magnetic circuit and the automotive environment. this small package can be easily assembled and used in conjunction with a wide variety of gear shapes and sizes. the integrated circuit incorporates a dual element hall-effect sensor with signal processing circuitry that switches in response to differential magnetic signals created by rotating ferrous targets. the device contains a sophisticated compensating circuit to eliminate magnet and system offsets immediately at power-on. digital tracking of the analog signal is used to achieve true zero-speed operation, while also setting the device switchpoints. the resulting switchpoints are air gap independent, greatly improving output and duty cycle accuracy. the device also uses a continuous update algorithm to fine- tune the switchpoints while in running mode, maintaining ats643-ds, rev. 2 features and benefits ? fully-optimized differential digital gear tooth sensor ? single chip-ic for high reliability ? internal current regulator for 2-wire operation ? small mechanical size (8 mm diameter x 5.5 mm depth) ? switchpoints air gap independent ? digital output representing gear profile ? precise duty cycle accuracy throughout temperature range ? large operating air gaps ? <2 ms power-on time self-calibrating, zero-speed differential gear tooth sensor with continuous update continued on the next page? functional block diagram not to scale packages: 4 pin sip (suffix sh) ats643lsh hall amp agc threshold logic thresholdp thresholdn pdac internal regulator vcc (pin 1) ndac gnd (pin 4) reference generator and updates offset adjust continued on the next page?
self-calibrating, zero-speed differential gear tooth sensor with continuous update ats643lsh 2 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com part number pb-free 1 packing 2 i cc typical ats643lshtn-i1-t yes tape and reel 13-in. 800 pcs./reel 6.0 low to 14.0 high ma ATS643LSHTN-I2-T yes tape and reel 13-in. 800 pcs./reel 7.0 low to 14.0 high ma 1 pb-based variants are being phased out of the product line. certain variants cited in this footnote are in production but have been determined to be not for new design. this classification indicates that sale of this device is currently restricted to existing customer applications. the device should not be purchased for new design applications because obsolescence in the near future is probable. samples are no longer available. status change: may 1, 2006. these variants include: ats643lshtn-i1 and ats643lshtn-i2. 2 contact allegro for additional packing options. 3 some restrictions may apply to certain types of sales. contact allegro for details. ? agc and reference adjust circuit ? true zero-speed operation ? undervoltage lockout ? wide operating voltage range ? defined power-on state the device specifications even through large changes in air gap or temperature. the regulated current output is configured for two-wire operation, offering inherent diagnostic information. this device is ideal for obtaining speed and duty cycle information in gear-tooth based applications such as transmission speed sensing. features and benefits (continued) description (continued) absolute maximum ratings characteristic symbol notes rating units supply voltage v cc see power derating section ? ? reverse-supply voltage v rcc ?18 v operating ambient temperature t a range l ?40 to 150 oc maximum junction temperature t j (max) 165 oc storage temperature t stg ?65 to 170 oc terminal list name description number vcc connects power supply to chip 1 nc no connection. float or tie to vcc 2 test for allegro use, float or tie to gnd 3 gnd ground terminal 4 2 4 3 1 inout diagram
self-calibrating, zero-speed differential gear tooth sensor with continuous update ats643lsh 3 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com operating characteristics using reference target 60-0, t a and v cc within specification, unless otherwise noted characteristic symbol test conditions min. typ. max. units electrical characteristics supply voltage v cc operating; t j < 165 c 4.0 ? 24 v undervoltage lockout v cc(uv) v cc 0 5 v ? 3.5 4.0 v supply zener clamp voltage v z i cc = 19 ma for ats643-i1, and 19.8 ma for ats643-i2; t a = 25c 28 ? ? v supply current i cc(low) ats643-i1 4.0 6 8.0 ma ats643-i2 5.9 7 8.4 ma i cc(high) ats643-i1 12.0 14.0 16.0 ma ats643-i2 11.8 14.0 16.8 ma supply current ratio i cc(high) / i cc(low) ratio of high current to low current 1.85 ? 3.05 ? power-on characteristics power-on state i cc(po) t < t on ; di/dt < 5 s ? high ? ma power-on time 1 t on target gear speed < 100 rpm ? 1 2 ms output stage output slew rate 2 di/dt r load = 100 , c load = 10 pf ? 7 ? ma/ s output state v out r sense on high side (vcc pin); i cc = i cc(high) ? low ? mv r sense on low side (gnd pin); i cc = i cc(high) ? high ? mv continued on the next page.
self-calibrating, zero-speed differential gear tooth sensor with continuous update ats643lsh 4 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com operating characteristics (continued) using reference target 60-0, t a and v cc within specification, unless otherwise noted characteristic symbol test conditions min. typ. max. units switchpoint characteristics rotation speed s rot reference target 60-0 0 ? 12,000 rpm bandwidth bw equivalent to f ? 3db 25 40 ? khz operate point b op % of peak to peak referenced from pdac to ndac, ag < ag max ?65? % release point b rp % of peak to peak referenced from pdac to ndac, ag < ag max ?35? % calibration 3 initial calibration period c i quantity of rising output (current) edges required for accurate edge detection ? ? 3 edge agc calibration disable c f quantity of rising output (current) edges used for calibrating agc ? ? 3 edge start mode hysteresis po hys ? 175 ? mv dac characteristics dynamic offset cancellation ? 60 ? g tracking data resolution quantity of bits available for pdac/ndac tracking of both positive and negative signal peaks ?9?bit functional characteristics air gap range 4 ag dc within specification 0.5 ? 2.5 mm maximum operable air gap ag (opmax) output switching (no missed edges); dc not guaranteed ? ? 2.75 mm duty cycle variation dc wobble < 0.5 mm, ag within specification ? ? 10 % input signal range sig dc within specification 40 ? 1400 g minimum operable input signal sig (opmin) output switching (no missed edges); dc not guaranteed 30 ? ? g 1 power-on time includes the time required to complete the internal automatic offset adjust. the dacs are then ready for peak acq uisition. 2 di is the difference between 10% of i cc(low) and 90% of i cc(high) , and dt is time period between those two points. note: di/dt is dependent upon the value of the bypass capacitor, if one is used. 3 continuous update (calibration) functions continuously during running mode operation. 4 ag is dependent on the available magnetic field. the available field is dependent on target geometry and material, and should b e independently characterized. the field available from the reference target is given in the reference target parameter section of the datashee t.
self-calibrating, zero-speed differential gear tooth sensor with continuous update ats643lsh 5 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com reference gear magnetic profile two tooth-to-valley transitions -700 -600 -500 -400 -300 -200 -100 0 100 200 300 400 500 600 700 0123456789101112 gear rotation () differential b* (g) 0.50 mm ag 2.00 mm ag 0.50 0.75 1.00 1.25 1.50 1.75 2.00 ag (mm) reference gear magnetic gradient amplitude with reference to air gap 0 200 400 600 800 1000 1200 1400 1600 1800 ag (mm) peak-to-peak differential b* (g) 0.5 1 1.5 2 2.5 reference target, 60-0 (60 tooth target) characteristics symbol test conditions typ. units symbol key outside diameter d o outside diameter of target 120 mm face width f breadth of tooth, with respect to sensor 6mm circular tooth length t length of tooth, with respect to sensor; measured at d o 3mm circular valley length t v length of valley, with respect to sensor; measured at d o 3mm tooth whole depth h t 3mm material low carbon steel ? ? *differential b corresponds to the calculated difference in the magnetic eld as sensed simultaneously at the two hall elements in the device (b diff = b e1 ? b e2 ). reference target 60-0 of sensor branded face
self-calibrating, zero-speed differential gear tooth sensor with continuous update ats643lsh 6 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com characteristic data data taken from 3 lots, 30 pieces/lot; i1 trim reference target 60-0 duty cycle at 1000 rpm 40 45 50 55 60 C50 0 50 100 150 200 t a (c) duty cycle (%) duty cycle at 1000 rpm 40 45 50 55 60 00.511.522.533.5 ag (mm) duty cycle (%) -40 0 25 85 150 duty cycle (25c) 40 45 50 55 60 0 500 1000 1500 2000 2500 rpm duty cycle (%) t a (oc) 3.0 2.75 2.5 2.25 2.0 1.5 1.0 0.5 ag (mm) 3.0 2.75 2.5 2.25 2.0 1.5 1.0 0.5 ag (mm) continued on the next page.
self-calibrating, zero-speed differential gear tooth sensor with continuous update ats643lsh 7 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com characteristic data (continued) data taken from 3 lots, 30 pieces/lot; i1 trim i cc (low) 3 4 5 6 7 8 9 C50 0 50 100 150 200 i cc (ma) i cc(low) 3 4 5 6 7 8 9 0 5 10 15 20 25 30 v cc (v) icc (ma) i cc(high) 11 12 13 14 15 16 17 C50 0 50 100 150 200 t a (c) i cc (ma) 26.5v 20v 12v 4v i cc(high) 11 12 13 14 15 16 17 0 5 10 15 20 25 30 v cc (v) icc (ma) t a (c) 26.5 20.0 12.0 4.0 v cc 26.5 20.0 12.0 4.0 v cc 150 85 25 0 C40 t a (oc) 150 85 25 0 C40 t a (oc) b op b rp b hys i cc(high) i cc i cc(low) switch to high switch to low b+ i+ hysteresis of i icc switching due to b outputcurrentinrelationtosensedmag- neticfluxdensity.transitionthroughb op mustprecedebytransitionthroughb rp .
self-calibrating, zero-speed differential gear tooth sensor with continuous update ats643lsh 8 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 min. typ. max units package thermal resistance r ja minimum-k pcb (single-sided with copper limited to solder pads) 126 ? ? oc/w low-k pcb (single-sided with copper limited to solder pads and 3.57 in. 2 (23.03 cm 2 ) of copper area) 84 ? ? 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 = 126 oc/w) minimum-k pcb (r ja = 84 oc/w) low-k 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 (m w) t j(max) = 165oc; v cc =v cc(max) ;i cc =i cc(max) maximum power dissipation, p d(max) (r ja =126o c/w) minimum-k pcb ( r ja = 84 oc/w) low-k p cb
self-calibrating, zero-speed differential gear tooth sensor with continuous update ats643lsh 9 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com sensing technology. the ats643 module contains a single-chip differential hall effect sensor ic, a samarium cobalt magnet, and a flat ferrous pole piece (concentrator). as shown in figure 1, the hall ic supports two hall elements, which sense the magnetic profile of the ferrous gear target simultaneously, but at different points (spaced at a 2.2 mm pitch), generating a differential internal analog voltage (v proc ) that is processed for precise switching of the digital output signal. the hall ic is self-calibrating and also possesses a tempera- ture compensated amplifier and offset cancellation circuitry. its voltage regulator provides supply noise rejection throughout the operating voltage range. changes in temperature do not greatly affect this device due to the stable amplifier design and the offset rejection circuitry. the hall transducers and signal processing electronics are integrated on the same silicon substrate, using a proprietary bicmos process. target profiling during operation. when proper power is applied to the sensor, it is capable of providing digital informa- tion that is representative of the mechanical features of a rotating gear. the waveform diagram in figure 3 presents the automatic translation of the mechanical profile, through the magnetic profile that it induces, to the digital output signal of the ats643. no additional optimization is needed and minimal processing circuitry is required. this ease of use reduces design time and functional description target (gear) back-biasing magnet south pole north pole case (pin 1 side) (pin n >1 side) hall ic pole piece element pitch (concentrator) dual-element hall effect device hall element 1 hall element 2 of sensor rotating target branded face 1 4 incremental assembly costs for most applications. determining output signal polarity. in figure 3, the top panel, labeled mechanical position , represents the mechani- cal features of the target gear and orientation to the device. the bottom panel, labeled sensor output signal , displays the square waveform corresponding to the digital output signal that results from a rotating gear configured as shown in figure 2. that direc- tion of rotation (of the gear side adjacent to the face of the sensor) is: perpendicular to the leads, across the face of the device, from the pin 1 side to the pin 4 side. this results in the sensor output switching from low, i cc(low) , to high, i cc(high) , as the leading edge of a tooth (a rising mechanical edge, as detected by the sensor) passes the sensor face. in this configuration, the device output current switches to its high polarity when a tooth is the target feature nearest to the sensor. if the direction of rotation is reversed, so that the gear rotates from the pin 4 side to the pin 1 side, then the output polarity inverts. that is, the output signal goes high when a falling edge is detected, and a valley is the nearest to the sensor. note, however, that the polarity of i out depends on the position of the sense resistor, r sense (see operat- ing characteristics table). continuous update of switchpoints . switchpoints are the threshold levels of the differential internal analog signal, v proc , at which the device changes output signal polarity. the value of figure 1. relative motion of the target is detected by the dual hall ele- ments mounted on the hall ic. figure 2. this left-to-right (pin 1 to pin 4) direction of target rotation results in a high output signal when a tooth of the target gear is nearest the face of the sensor (see figure 3). a right-to-left (pin 4 to pin 1) rota- tion inverts the output signal polarity. figure 3. the magnetic profile reflects the geometry of the target, allow- ing the ats643 to present an accurate digital output response. b op(#1) b rp(#1) b op(#2) on off off on sensor internal switch state sensor orientation to target sensor internal differential analog signal, v proc mechanical position (target movement pin 1 to pin 4) sensor output signal, i out target (gear) sensor sensor branded face pin 1 side pin 4 side +t target magnetic profile +b +t +t this tooth sensed earlier this tooth sensed later
self-calibrating, zero-speed differential gear tooth sensor with continuous update ats643lsh 10 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com v proc is directly proportional to the magnetic flux density, b, induced by the target and sensed by the hall elements. when v proc transitions through a switchpoint from the appropriate higher or lower level, it triggers sensor switch turn-on and turn- off. as shown in figure 3, when the switch is in the off state, as v proc rises through a certain limit, referred to as the operate point , b op , the switch toggles from off to on. when the switch is in the on state, as v proc falls below b op to a certain limit, the b hys(#1) pk (#4) pk (#5) pk (#7) pk (#9) pk (#2) pk (#3) pk (#1) pk (#6) pk (#8) v proc (v) b rp(#1) b op(#1) b rp(#2) b rp(#3) b op(#3) b rp(#4) b op(#4) b hys(#4) b hys(#3) b hys(#2) t+ v+ b op(#2) (a) teag varying; cases such as eccentric mount, out-of-round region, normal operation position shift (b) internal analog signal, v proc , typically resulting in the sensor 0 360 target rotation () hysteresis band (delimited by switchpoints) v proc (v) v+ larger teag smaller teag sensor target larger teag target sensor smaller teag smaller teag release point , b rp , the switch toggles from on to off. as shown in panel c of figure 4, threshold levels for the ats643 switchpoints are established dynamically as function of the peak input signal levels. the ats643 incorporates an algorithm that continuously monitors the system and updates the switch- ing thresholds accordingly. the switchpoint for each edge is determined by the detection of the previous two edges. in this manner, variations are tracked in real time. figure 4. the continuous update algorithm allows the allegro sensor to immediately interpret and adapt to significant variances in the magnetic field generated by the target as a result of eccentric mounting of the target, out-of-round target shape, elevation due to lubricant build-up in journal gears, and similar dynamic application problems that affect the teag (total effective air gap). the algorithm is used to dynamically estab lish and subsequently update the device switchpoints (b op and b rp ). the hysteresis, b hys(#x) , at each target feature configuration results from this recalibration, ensuring that it remains properly proportioned and centered within the peak-to-peak range of the internal analog signal, v proc . as shown in panel a, the variance in the target position results in a change in the teag. this affects the sensor as a varying magnetic field, which results in proportional changes in the internal analog signal, v proc , shown in panel b. the continuous update algorithm is used to establish accurate switchpoints based on the fluctuation of v proc , as shown in panel c. (c) referencing the internal analog signal, v proc , to continuously update device response b hys switchpoint determinant peak values 1 b op(#1) pk (#1) , pk (#2) b rp(#1) pk (#2) , pk (#3) 2 b op(#2) pk (#3) , pk (#4) b rp(#2) pk (#4) , pk (#5) 3 b op(#3) pk (#5) , pk (#6) b rp(#3) pk (#6) , pk (#7) 4 b op(#4) pk (#7) , pk (#8) b rp(#4) pk (#8) , pk (#9)
self-calibrating, zero-speed differential gear tooth sensor with continuous update ats643lsh 11 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com power-on state operation . the ats643 is guaranteed to power-on in the high current state, i cc(high) . initial edge detection . the device self-calibrates using the initial teeth sensed, and then enters running mode. this results in reduced accuracy for a brief period (less than four teeth), however, it allows the device to optimize for continuous update yielding adaptive sensing during running mode. as shown in figure 5, the first three high peak signals are used to calibrate agc. however, there is a slight variance in the duration of ini- tialization, depending on what target feature is nearest the sensor when power-on occurs. figure 5. power-on initial edge detection. this figure demonstrates four typical power-on scenarios. all of these examples assu me that the target is moving relative to the sensor in the direction indicated. the length of time required to overcome start mode hysteresis, as wel l as the combined effect of whether it is overcome in a positive or negative direction plus whether the next edge is in that same or opposite polarity, affect the point in time when agc calibration begins. three high peaks are always required for agc calibration. target (gear) output v proc v proc v proc v proc output output output power-on over valley power-on at rising edge power-on over tooth power-on at falling edge agc calibration running mode agc calibration running mode agc calibration running mode agc calibration running mode sensor position 1 3 4 2 1 2 4 3 start mode hysteresis overcome start mode hysteresis overcome start mode hysteresis overcome start mode hysteresis overcome
self-calibrating, zero-speed differential gear tooth sensor with continuous update ats643lsh 12 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com start mode hysteresis . this feature helps to ensure optimal self-calibration by rejecting electrical noise and low-amplitude target vibration during initialization. this prevents agc from calibrating the sensor on such spurious signals. calibration can be performed using the actual target features. a typical scenario is shown in figure 6. the hysteresis, po hys , is a minimum level of the peak-to-peak amplitude of the internal analog electrical signal, v proc , that must be exceeded before the ats643 starts to compute switchpoints. figure 6. operation of start mode hysteresis position 1. at power-on, the ats643 begins sampling v proc . position 2. at the point where the start mode hysteresis is exceeded, the device begins to establish switching thresholds (b op and b rp ) using the con- tinuous update algorithm. after this point, start mode hysteresis is no longer a consideration. note that a valid v proc value exceeding the start mode hysteresis can be generated either by a legitimate target feature or by excessive vibration. position 3. in this example, the first switchpoint transition is through b op . and the output transitions from high to low. if the first switchpoint transition had been through b rp (such as position 4), no output transition would occur because i out already would be in the high polarity. the first transition would occur at position 5 (b op ). b rp(#1) b op(#1) b op(#2) 1 3 4 5 5 2 1 2 start mode hysteresis, po hys output signal, i out sensor position relative to target target magnetic profile differential signal, v proc target, gear
self-calibrating, zero-speed differential gear tooth sensor with continuous update ats643lsh 13 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com undervoltage lockout . when the supply voltage falls below the minimum operating voltage, v cc(uv) , i cc goes high and remains high regardless of the state of the magnetic gradi- ent from the target. this lockout feature prevents false signals, caused by undervoltage conditions, from propagating to the output of the sensor. power supply protection . the device contains an on-chip regulator and can operate over a wide v cc range. for devices that need to operate from an unregulated power supply, transient protection must be added externally. for applications using a regulated line, emi/rfi protection may still be required. contact allegro microsystems for information on the circuitry needed for compliance with various emc specifications. refer to fig- ure 7 for an example of a basic application circuit. automatic gain control (agc) . this feature allows the device to operate with an optimal internal electrical signal, regardless of the air gap (within the ag specification). at power-on, the device determines the peak-to-peak amplitude of the signal generated by the target. the gain of the sensor is then automatically adjusted. figure 8 illustrates the effect of this feature. automatic offset adjust (aoa) . the aoa is patented cir- cuitry that automatically cancels the effects of chip, magnet, and installation offsets. (for capability, see dynamic offset cancel- lation, in the operating characteristics table.) this circuitry is continuously active, including both during power-on mode and running mode, compensating for any offset drift. continuous operation also allows it to compensate for offsets induced by temperature variations over time. assembly description. the ats643 is integrally molded into a plastic body that has been optimized for size, ease of assembly, and manufacturability. high operating temperature materials are used in all aspects of construction. 2 ats643 1 3 4 vcc 0.01 f 100 (optional) (optional) figure 7. typical basic circuit for proper device operation. mechanical profile ag small ag large ag small ag large internal differential analog signal response, with agc internal differential analog signal response, without agc ferrous target v+ v+ figure 8. automatic gain control (agc). the agc function corrects for variances in the air gap. differences in the air gap cause differences in the magnetic field at the device, but agc prevents that from affecting device performance, a shown in the lowest panel.
self-calibrating, zero-speed differential gear tooth sensor with continuous update ats643lsh 14 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (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 l-i1, using minimum-k pcb observe the worst-case ratings for the device, specifically: r ja = 126c/w, t j(max) = 165c, v cc(max) = 24 v, and i cc(max) = 16 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 126 c/w = 119 mw finally, invert equation 1 with respect to voltage: v cc(est) = p d(max) i cc(max) = 119 mw 16 ma = 7 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.
self-calibrating, zero-speed differential gear tooth sensor with continuous update ats643lsh 15 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com package sh, 4-pin sip 1.08 .043 8.0 .315 5.5 .217 0.38 .015 5.0 .244 5.8 .228 4.0 .157 1.7 .067 1 .039 0.6 .024 0.6 .024 1.27 .050 20.95 .825 13.05 .514 dimensions in millimeters. untoleranced dimensions are nominal. u.s. customary dimensions (in.) in brackets, for reference only 24 3 1 a a a b c d d b dambar removal protrusion (16x) metallic protrusion, electrically connected to pin 4 and substrate (both sides) active area depth thermoplastic molded lead bar for alignment during shipment
self-calibrating, zero-speed differential gear tooth sensor with continuous update ats643lsh 16 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 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 current. 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, 2006 allegro microsystems, inc.

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