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the A1232 is a highly sensitive, temperature-stable magnetic sensing device ideal for use in ring-magnet-based speed and direction systems in harsh automotive and industrial environments. it contains two bipolar, hall-effect switches precisely arranged 1.63 mm apart. the switch outputs are thus in quadrature when interfaced with the proper ring magnet design. internal logic processes the resulting digital signals to derive speed and direction information that is presented at the devices outputs, output a and output b. the A1232 is designed for demanding, high-performance motor commutation applications. the hall elements are photolithographically aligned to better than 1 m. accurately locating the two hall elements eliminates a major manufacturing hurdle encountered in fine-pitch applications. the A1232 also has true power-on state (tpos), the ability to detect when it is in the hysteresis band, beyond b op , or below b rp at power-on. this provides reduced angle accuracy error due to missed start-up edges. post-assembly factory programming at allegro provides sensitive, symmetrical switchpoints for both switches. extremely low-drift amplifiers maintain this symmetry. the allegro? patented, high-frequency chopper stabilization technique cancels offsets in each channel and allows for increased signal-to-noise ratio at the input of the internal comparators. this leads to stable operation across the A1232-ds, rev. 1 ? aec q100 automotive qualified ? senses speed and direction of ring magnets two matched bipolar hall-effect switches on a single substrate true power-on state (tpos): recognizes hysteresis region at power-on ? superior temperature stability ? internal regulator for 3.3 to 24 v operation ? symmetrical, high-sensitivity switchpoints ? automotive grade solid-state reliability integrated esd diodes robust structures for emc protection short-circuit protected outputs reverse battery protection C40c to +150c operating range ultra-sensitive, hall-effect speed and direction sensor with tpos package: 8-pin tssop (suffix le) functional block diagram not to scale A1232 continued on next page... features and benefits description channela channel b hall element e1 hall element e2 dynamic offse t cancellatio n dynamic offse t cancellatio n hall amp. hall amp. low- pass filter low- pass filter low noise signa l recovery low noise signa l recovery output drive an d high resolutio n speed logi c output drive an d direction logi c programmabl e t rim ldo regulato r gnd output a (speed) output b (direction) vcc 4 bit 2 bit 2 bit
2 description (continued) operating temperature and voltage ranges and industry leading jitter performance. an on-chip regulator provides a wide operating voltage range. the A1232 is packaged in a plastic 8-pin surface mount tssop (le). this gull-wing style package is optimized for the extended temperature range of C40c to 150c. it is lead (pb) free and rohs-compliant, with a 100% matte-tin-plated leadframe. selection guide part number packing* mounting ambient (t a ) A1232lletr-t 4000 units per reel 8-pin tssop surface mount C40oc to 150oc *contact allegro ? for additional packing options. table of contents specifications 3 absolute maximum ratings 3 pin-out diagram and terminal list table 3 thermal characteristics 4 common electrical characteristics 5 electrical operating characteristics 7 magnetic operating characteristics 8 magnetic truth table 11 functional desription 12 typical applications operation 12 power-on sequence timing 14 true power-on state (tpos) 14 target design and selection 15 operation with fine-pitch ring magnets 16 chopper-stabilized technique 17 regulated supply 18 unregulated supply 18 power derating 20 package outline drawing 21 rohs compliant ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
3 absolute maximum ratings characteristic symbol notes rating unit forward supply voltage v cc 26.5 v reverse supply voltage v rcc C18 v output off voltage v out(off) v cc v output sink current i out internally limited C magnetic flux density b unlimited C operating ambient temperature t a range l C40 to 150 oc maximum junction temperature t j(max) 165 oc storage temperature t stg C65 to 170 oc specifications package le, 8-pin tssop pin-out diagram terminal list table name number function 3 vcc connects power supply to chip 4 output b start-up mode: output from e2 via first schmitt circuit running mode: direction 5 output a start-up mode: output from e1 via second schmitt circuit running mode: high-resolution speed 6 gnd terminal for ground connection 1, 2, 7, 8 nc no connections 1 2 3 45 6 7 8 pin-out diagram and terminal list table ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
4 thermal characteristics: may require derating at maximum conditions; see power derating section. characteristic symbol test conditions 1 value units package thermal resistance r ja on 4-layer pcb based on jedec standard jesd51-7 145 oc/w 1 additional thermal information is available on the allegro? web site, www.allegromicro.com power dissipation versus ambient t emperature t emperature (oc) t emperature (oc) v cc(max) v cc(min) power derating curve power dissipation, p (mw) d maximum allowable vcc (v) package le, 4-layer pcb (r = 145oc/w) ja 1000 900 800 700 600 500 400 300 200 100 0 20 20 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 40 40 60 60 80 80 100 100 120 120 140 140 160 160 180 180 package le, 4-layer pcb (r = 145oc/w) ja ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
5 characteristic symbol test conditions min. typ. max. units electrical characteristics 2 supply voltage 3 v cc operating: t a 150oc 3.3 C 24 v output leakage current i off either output C <1 10 a supply current i cc 2.5 3.7 6.0 ma low output voltage v out(on) i out = 20 ma b > b op(a) , b > b op(b) C 185 500 mv middle output voltage 4 v out(mid) b rp < b < b op , v pull-up = 12 v, r load = 12 k C 6 C v output sink current, middle i out(mid) b rp < b < b op , v pull-up = 12 v, r load = 12 k C 0.5 C ma output sink current limit i om v cc = 12 v 30 C 70 ma chopping frequency f c C 750 C khz output rise time 5 t r c s = 20 pf, r load = 820 C 1.8 C s output fall time 5 t r c s = 20 pf, r load = 820 C 1.2 C s power-on time 6 t on C 50 65 s power-on state 7 pos t < t on b = 0 g v out(off) C t t on b rp b op v out(on) C b < b rp v out(off) C transient protection characteristics supply zener clamp voltages v z i cc = 9 ma, t a = 25oc 28 46 C v supply zener current 8 i z v s = 28 v C C 9.0 ma reverse supply current i rcc v rcc = C18 v, t j < t j(max) C 2 15 ma electrical characteristics: valid over full operating temperature range unless otherwise noted; typical data applies to v cc = 12 v and t a = 25c; see typical application circuits 2 output related specifications listed in the characteristic column are applicable to each output transistor unless otherwise noted. 3 maximum voltage operation must not exceed maximum junction temperature. refer to power de-rating curves. 4 v out(mid) and i out(mid) specified typical values are found when connected as shown in figure 10 and figure 11. this information is only guaranteed available before the first magnetic field transition has occurred and after the power-on time has occurred. the output state transition from the t < t on pos and the t > t on pos is not considered the first magnetic field transition. see figure 1 and the magnetic truth table for power-on behavior. 5 c s = oscilloscope probe capacitance 6 power-on time is the duration from when v cc rises above v cc(min) until both outputs have attained valid states. 7 pos for both outputs is undefined for v cc < v cc(min) . use of a v cc slew rate greater than 25 mv/s is recommended. 8 maximum specification limit is equivalent to i cc(max) + 3 ma. ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
6 characteristic symbol test conditions min. typ. max. units magnetic characteristics 10 operate point: b > b op b op(a) , b op(b) C 10 30 g release point: b < b rp b rp(a) , b rp(b) C30 C10 C g hysteresis: b op(a) - b rp(a) , b op(b) - b rp(b) b hys(a) , b hys(b) 5 20 35 g symmetry: ch a, ch b b op(a) + b rp(a) , b op(b) + b rp(b) sym a , sym b C35 C 35 g operate symmetry: b op(a) C b op(b) sym ab(op) C25 C 25 g release symmetry: b rp(a) C b rp(b) sym ab(rp) C25 C 25 g magnetic characteristics: valid over full operating temperature range unless otherwise noted; typical data applies to v cc = 12 v and t a = 25c; see typical application circuits 9 1g (gauss) = 0.1 mt (millitesla) 10 magnetic flux density, b, is indicated as a negative value for north-polarity magnetic fields, and as a positive value for south-polarity magnetic fields. the algebraic conven - tion used here supports arithmetic comparison of north and south polarity values, where the relative strength of the field is indicated by the absolute value of b, and the sign indicates the polarity of the field (for example, a C100 g field and a 100 g field have equivalent strength, but opposite polarity). 9 ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
7 electrical operating characteristics a verage supply current versus supply v oltage i (ma) cc v (v) cc 2 61 01 41 82 22 6 5.5 6.0 6.5 2.5 3.0 3.5 4.0 4.5 5.0 t (oc) a -40 25 150 a verage supply current versus ambient t emperature i (ma) cc t (oc) a -60- 40 -200 20 40 60 80 100 120 140 160 5.5 6.0 6.5 2.5 3.0 3.5 4.0 4.5 5.0 v( v) cc 3.3 12 24 a verage low output v oltage versus ambient t emperature for i= 20 ma out v (mv) out(on) t (oc) a -60- 40 -200 20 40 60 80 100 120 140 160 300 350 450 400 500 0 50 100 150 200 250 v( v) cc 3.3 12 24 ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
8 magnetic characteristics channel a: a verage operate & release points versus supply v oltage b & b (g) op rp v (v) cc 2 61 0 14 18 22 26 10 20 30 -30 -20 -10 0 t (oc) a -40 25 150 b op -40 25 150 b rp channel a: a verage operate & release points versus ambient t emperature b & b (g) op rp t a (oc) -60 -40- 20 02 04 06 08 0 100 120 140 160 10 20 30 -30 -20 -10 0 v cc (v) 3.5 12 24 b op 3.5 12 24 b rp channel b: a verage operate & release points versus supply v oltage b & b (g) op rp v (v) cc 2 61 0 14 18 22 26 10 20 30 -30 -20 -10 0 t (oc) a -40 25 150 b op -40 25 150 b rp channel b: a verage operate & release points versus ambient t emperature b & b (g) op rp t a (oc) -60 -40- 20 02 04 06 08 0 100 120 140 160 10 20 30 -30 -20 -10 0 v cc (v) 3.5 12 24 b op 3.5 12 24 b rp channel a& b: a verage switchpoint hysteresis versus supply v oltage b & b (g) hys(a) hys(b) v (v) cc 2 61 0 14 18 22 26 10 15 20 25 30 35 0 5 t (oc) a -40 25 150 ch. a -40 25 150 ch. b channel a& b: a verage switchpoint hysteresis versus ambient t emperature b & b (g) hys(a) hys(b) t a (oc) -60 -40- 20 02 04 06 08 0 100 120 140 160 v cc (v) 3.5 12 24 ch. a 3.5 12 24 ch. b 10 15 20 25 30 35 0 5 additional magnetic characteristics on next page. ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
9 a verage operate point symmetry versus supply v oltage sym ab(op) (g) v cc (v) 2 61 0 14 18 22 26 5 10 20 15 25 -25 -20 -15 -10 -5 0 t a (oc) -40 25 150 a verage operate point symmetry versus ambient t emperature sym ab(op) (g) t (oc) a -60- 40 -200 20 40 60 80 100 120 140 160 5 10 20 15 25 -25 -20 -15 -10 -5 0 v( v) cc 3.3 12 24 a verage release point symmetry versus supply v oltage sym ab(rp) (g) v cc (v) 2 61 0 14 18 22 26 5 10 20 15 25 -25 -20 -15 -10 -5 0 t a (oc) -40 25 150 a verage release point symmetry versus ambient t emperature sym ab(rp) (g) t (oc) a -60- 40 -200 20 40 60 80 100 120 140 160 5 10 20 15 25 -25 -20 -15 -10 -5 0 v( v) cc 3.3 12 24 additional magnetic characteristics on next page. continued from previous page. ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
10 channel b symmetry versus supply v oltage sym b (g) v cc (v) 2 61 0 14 18 22 26 7 14 28 21 35 -35 -28 -21 -14 -7 0 t a (oc) -40 25 150 channel b symmetry versus ambient t emperature sym b (g) t (oc) a -60- 40 -200 20 40 60 80 100 120 140 160 7 14 28 21 35 -35 -28 -21 -14 -7 0 v( v) cc 3.3 12 24 continued from previous page. channel a symmetry versus supply v oltage sym a (g) v cc (v) 2 61 0 14 18 22 26 7 14 28 21 35 -35 -28 -21 -14 -7 0 t a (oc) -40 25 150 channel a symmetry versus ambient t emperature sym a (g) t (oc) a -60- 40 -200 20 40 60 80 100 120 140 160 7 14 28 21 35 -35 -28 -21 -14 -7 0 v( v) cc 3.3 12 24 ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
11 conditions magnetic field b e1 at hall element e1 magnetic field b e2 at hall element e2 outa outb t < t on C C x x t > t on power-on time has occurred and fields b e1 and b e2 have not yet each transitioned b e1 b op(b) h l b rp(a) b op(b) m l b e1 > b op(a) b e2 b op(a) b rp(b) b op(a) b e2 > b op(b) l l t > t on & b e1 and b e2 have already each transitioned at least one time any any spd dir key l = v out(on) , low m = v out(mid) , middle h = v out(off) , high spd = high-resolution speed dir = direction x = output not defined magnetic truth table ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
12 functional description typical applications operation as shown in figure 1, the bipolar hall-effect switches in the A1232 turn on when a south-polarity magnetic field perpendicu - lar to the hall element exceeds the operate point threshold (b op ); the switches turn off when a north-polarity magnetic field of suf - ficient strength exceeds the release point (b rp ) the difference in the magnetic operate and release points is the hysteresis (b hys ) of the device. b hys = b op - b rp this built-in hysteresis allows clean switching of the output even in the presence of external mechanical vibration and electrical noise. v+ v out(off) switch to low switch to high v out(on) v output b- 0 b+ b rp b op b hys the hall-effect sensing elements are precisely located 1.63 mm apart across the width of the package (see figure 2: A1232 sensors and relationship to target). when used with a properly designed ring magnet, the outputs of the two switches will be in quadrature, or 90 degrees out of phase. the relationship of the various signals and the typical system timing is shown in figure 3: typical system timing. during operation (run mode), the output of the internal switches is encoded into a pair of signals representing the speed and direction of the target (see functional block diagram on page 1). these signals appear at the output a (speed) and output b (direction) pins. output b (direction) is a logic signal indicating the direction of rotation (assuming a ring magnet target). it is defined as off (high) for targets moving in the direction from e1 to e2 and on (low) for the direction e2 to e1. for instances when the rotation direction of the target changes, output b changes state and then the speed output (output a) resumes after a short delay (t d , approximately 3 to 5 s). output b (direction) is always updated before output a (speed) and is updated at each hall elements switching transition. this sequencing and built-in delay allow the tracking of target speed or position with an external counter without the loss of pulses. output a (speed) is a logic output representing the combined (xored) outputs of the two hall-effect switches. this produces a digital output edge at each switchs transition beyond b op and b rp . it will change state as the magnetic poles pass across the device at a rate given by equation a and with a period given by equation b: f (hz) = output a t (s) = output a v 1 60 seconds f output a 2 (a) (b) example for = 2 and v = 60 rpm (based on target depicted in figure 3): pcb n n s s z e 2 to e 1 o u tp u t b (d irectio n ) = o n (l o w ) e 1 to e 2 o u tp u t b (d irec tion ) = o ff (h ig h ) 8 1 e2 e1 figure 2: A1232 sensor and relationship to target figure 1: output voltage in relation to magnetic flux density received ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
13 f (hz) = output a t (s) = output a 60 2 1 60 seconds 4 hz 2 = 4 hz =250 ms key: ? v = axle shaft speed (rpm) ? = number of north and south pole-pairs per axle mechanical revolution ? f = cycles per second (hz) ? t = time duration of one mechanical period (s) immediately after turn-on, the device will be in a special true power-on state (tpos) mode. this mode allows the device to detect and indicate that one or both of the switches is in the hys - teresis region, i.e., that the applied field is between b op and b rp . ring magnet starts rotating magnetic field at hall element e1 (pin 1 side) magnetic field at hall element e2 (pin 8 side) internal channel a internal channel b direction output b xor speed output a v = v out(off) v = v out(on) pin 1 to 8 t on pos second hall t ransition first hall t ransition t expires (typ. 50 s) on power on pin 8 to 1 t d b rp(e1) b op(e2) b op(e1) b rp(e2) internal stage output stage time + v = v out(mid ) d i r e c t i o n c h a n g e figure 3: typical system timing ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
14 power-on sequence and timing the states of output a and output b are only valid when the supply voltage is within the specified operating range (v cc(min) v cc v cc(max) ) and the power-on time has elapsed ( t > t on ). refer to figure 4: power-on sequence and timing for an illustration of the power-on sequence. true power-on state (tpos) immediately after power-on (figure 4, after t on has elapsed), output a and output b will follow the state of the corre - sponding switches rather than the outputs of the speed and direc - tion logic. this mode allows the device to detect and indicate that one or both of the switches is in the hysteresis region (i.e., that the applied field is between b op and b rp ). additionally while in tpos mode, the outputs will report if the corresponding switch is beyond b op or below b rp . these output states, v out(on) for b > b op and v out(off) for b < b rp , reflect the output polarity and level corresponding to the target feature (magnet pole) nearest the switch. in run mode, the outputs will be driven only either high or low, that is, to v out(off) or v out(on) , as the A1232 indicates the movement of the target. (the precise voltage levels are dictated by the load circuit and pull-up voltage on each output.) while the A1232 is in tpos mode and either or both of the sensors are in their hysteresis range (b op < b < b rp ), a third state is present on the corresponding output as shown in figure 5: power-on state vs. applied field. dynamic current limiting circuitry holds the output sink current at i out(mid) , creating an output state known as v out(mid) . the output voltage corresponding to v out(mid) is given by: v out(mid) = v out(off) - [i out(mid) r load ] by choosing the correct load resistor, r load , this middle output state can be made equal to half of the pull-up voltage. this is the case when using the typical application circuits shown in figures 10 and 11. see the circuit analysis example table following the typical application circuits for more details. the host must be able to detect this middle state in order to make use of the tpos information. after exiting tpos mode, only the standard low (v out(on) ) and high (v out(off) ) output states are produced to indicate target speed and direction. both outputs exit tpos mode together, and only after each switch has detected a magnetic field transition from their power-on state (that is, beyond b op or b rp ). internal comparators prevent the outputs from entering the i out(mid) state if it was not activated at the moment of power-on. once having exited tpos mode, the outputs will not re-enter tpos mode as long as power is maintained. note: the states of output a and output b are only valid when the supply voltage is within the specifed oper - ating range and the power-on time has elapsed. see power-on sequence and timing for details. b b op v cc v cc(min) v out(off) v out(mid) v out(on) output unde?ned for v< v cc cc(min) v v 0 0 t on time time figure 4: power-on sequence and timing v+ v out(off) v out(mid) v out(on) v output b- b+ b rp b op b hys figure 5: power-on state vs. applied field ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
15 target design/selection internal logic circuitry produces outputs representing the speed (output a) and direction (output b) of the magnetic field passing across the face of the package. the response of the device to the magnetic field produced by a rotating ring magnet is shown in figure 3. (note the phase shift between the two integrated hall elements.) for the direction signal to be correct, the switch points of the hall elements must be adequately matched and a quadrature relation - ship must be maintained between the targets magnetic poles and the spacing of the two hall elements (e1 and e2). a quadrature relationship produces hall switch phase separation of 90. for optimal performance, the device should be actuated by a ring magnet that presents to the front of the device fields with a pole pitch two times the hall element-to-element spacing of 1.63 mm. the period (t) is then equal to twice the pole pitch (p), as depicted by figure 6 and equation c. this will produce a sinu - soidal magnetic field whose period corresponds to four times the element-to-element spacing: for p = 2 1.63 mm = 3.26 mm (c) t = 2 3.26 mm = 6.52 mm the A1232 requires a minimum magnetic field input to guarantee switching, as described in equation d: b pk-pk = b op(max) + |b rp(min) |, (d) b pk-pk = 30 g + 30 g = 60 g based on the maximum operate point (b op(max) ) and the mini - n n s s s e1 e2 pin 1 air gap pin 8 A1232 branded fac e of package element pitch direction of rotatio n ring magnet figure 6a: device orientation to target ns ss n direction of rotatio n ring magnet t arget +b -b element pitch t arget magnetic pro?le figure 6b: mechanical position (target moves past device pin 1 to pin 8) figure 6: target profling during operation 40 30 20 10 0 -10 -20 -30 -40 0 + b (s) op(max) b( n) rp(min) ti me flux density , b (g ) figure 7a: example of ring target magnetic profile 800 700 600 500 400 300 200 100 0 0 + air gap peak-to-peak flux density , b (g) pk-pk figure 7b: example of ring magnetic flux density peak-to-peak vs. air gap figure 7: example of target magnetic field profle ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
16 mum release point (b rp(min) ), it is recommended to ensure the targets magnetic input signal remains above 60 g peak-to-peak when centered about 0 g. if the system has a magnetic offset component present, field values b op and b rp must be exceeded to continue switching. thus for optimal performance it is rec - ommended to interface the sensor with an alternating bipolar magnetic field profile that continuously exceeds b op(max) and b rp(min) . as depicted in figure 7, the sinusoidal profile created by the alternating north and south poles of a rotating ring magnet decreases in magnitude as the air gap is increased. the minimum peak-to-peak flux density must be accounted for in system air gap tolerances. operation with fine-pitch ring magnets for targets with a circular pitch of less than 4 mm, a performance improvement can be observed by rotating the front face of the device (refer to figure 8). this rotation decreases the effective hall element-to-element spacing (d), provided that the hall ele - ments are not rotated beyond the width of the target. e1 e1 e2 e2 s n s d d cos t arget pro?le of rotation t arget circular pitch (p) t arget face width (f) f < d sin a rotated alignment normal coplanar alignment figure 8: operation with fine-pitch ring magnets ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
17 a limiting factor for switch point accuracy when using hall- effect technology is the small signal voltage developed across the hall plate. this voltage is proportionally small relative to the offset that can be produced at the output of the hall sensor. this makes it difficult to process the signal and maintain an accurate, reliable output over the specified temperature and voltage range. chopper stabilization is a proven approach used to minimize hall offset. the allegro patented technique, dynamic quadrature offset cancellation, removes key sources of the output drift induced by temperature and package stress. this offset reduction technique is based on a signal modulation-demodulation process. figure 9: example of chopper stabilization circuit (dynamic offset cancellation) illustrates how it is implemented. the undesired offset signal is separated from the magnetically induced signal in the frequency domain through modulation. the subsequent demodulation acts as a modulation process for the offset causing the magnetically induced signal to recover its original spectrum at baseband while the dc offset becomes a high frequency signal. then, using a low-pass filter, the signal passes while the modulated dc offset is suppressed. allegros innovative chopper-stabilization technique uses a high frequency clock. the high-frequency operation allows a greater sampling rate that produces higher accuracy, reduced jitter, and faster signal processing. additionally, filtering is more effective and results in a lower noise analog signal at the sensor output. devices such as the A1232 that utilize this approach have an extremely stable quiescent hall output voltage, are immune to thermal stress, and have precise recoverability after temperature cycling. this technique is made possible through the use of a bicmos process which allows the use of low offset and low noise amplifiers in combination with high-density logic and sample and hold circuits. chopper stabilization technique regulator amp low- pass filter sample and hold figure 9: example of chopper stabilization circuit (dynamic offset cancellation) ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
18 regulated supply this device requires minimal protection circuitry for operation from a regulated power supply. the on-chip voltage regulator provides immunity to power supply variations between 3.3 v and 18 v. because the device has open-drain outputs, pull-up resistors must be used. if protection against coupled and injected noise is required, then a simple bypass capacitor filter is recommended. refer to the circuit in figure 10 for an example. unregulated supply in applications where the A1232 receives its power from an unregulated source such as a car battery, additional measures may be required to protect it against supply-side transients. specifica - tions for such transients will vary so protection-circuit design should be optimized for each application. for example, the circuit shown in figure 11 includes an optional zener diode that offers additional high voltage load-dump protection and noise filtering by means of a series resistor and capacitor. in addition to this, an optional series diode is included, and this protects against high- voltage reverse battery conditions beyond the capability of the built-in reverse-battery protection. v output a v suppl y v output b r= load 12 k r= load 12 k 100 nf + 3 4 5 6 gnd vcc output a output b A1232 figure 10: typical application circuit for regulated power supply v outpu ta v suppl y v outpu tb r= load 12 k r= load 12 k c= out 4.7 nf c= out 4.7 nf 100 100 nf + ++ 3 a a ad iodes are optional for systems not exceeding v and v depending on z rcc conducted immunity requirements. 4 5 6 gnd vcc output a output b A1232 figure 11: typical application circuit for unregulated power supply ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
19 v suppl y c output(a) c output(b) i output(a) i output(b) v pull-up(a) v pull-up(b) r load(a) r load(b) 3 4 5 out a outb to all subcircuits 6 A1232 + + + figure 12: application circuit example table 1: circuit analysis example startup operation analysis condition v pull-up(a/b) (v) r load(a/b) () output (v) i output(a/b) (internally limited) t > t on before first magnetic field transition of each channel b rp t on after first magnetic field transition of each channel b > b op 3.3 2.8 k 500 1 5 4.5 k 500 1 12 11.84 k 160 1 18 875 500 20 12 except for the 12 v typical calculations, the output on voltage is assumed worse case of 500 mv. actual application values will vary. 13 output sink current calculations are for demonstrational purposes only and actual i out(on) and v out(on) values will vary with different pull-up source and resistor values, in addition to t j and v cc . during normal operation the devices output sink current is internally limited to between 30 ma and 70 ma. ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
20 power derating the device must be operated below the maximum junction tem - perature of the device (t j(max) ). under certain combinations of peak conditions, reliable operation may require derating supplied power or improving the heat dissipation properties of the appli - cation. this section presents a procedure for correlating factors affecting operating t j (thermal data is also available on the allegro microsystems web site, www.allegromicro.com). 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 or 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 = 145c/w, then: p d = v cc i cc = 12 v 4 ma = 48 mw t = p d r ja = 48 mw 145c/w = 7c t j = t a + t = 25c + 7c = 32c a worst-case estimate (p d (max) ) represents the maximum allow - able power level, without exceeding t j (max) , at a selected r ja and t a . example: reliability for v cc at t a = 150c, package le, using a four-layer pcb. observe the worst-case ratings for the device, specifically: r ja = 145c/w, t j (max) = 165c, v cc (max) = 24 v, and i cc (max) = 6 ma. calculate the maximum allowable power level (p d (max) ). first, invert equation 3: t (max) = t j (max) C t a = 165c C 150c = 15c this provides the allowable increase to t j resulting from internal power dissipation. then, invert equation 2: p d (max) = t (max) r ja p d (max) = 15c 145c/w = 103 mw finally, invert equation 1 with respect to voltage: v cc (est) = p d (max) i cc (max) v cc (est) = 103 mw 6 ma = 17.2 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 vcc (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. in cases where the v cc (max) level is known, and the system designer would like to determine the maximum allowable ambi - ent temperature (t a (max) ), the calculations can be reversed. for example, in a worst case scenario with conditions v cc (max) = 24 v and i cc (max) = 6 ma, using equation 1 the largest possible amount of dissipated power is: p d = v in i in p d = 24 v 6 ma = 144 mw then, by rearranging equation 3: t a (max) = t j (max) C t t a (max) = 165c/w C (144 mw 145c/w) t a (max) = 165c/w C 20.88c = 144.12c in another example, the maximum supply voltage is equal to v cc(min) . therefore, v cc (max) = 3.3 v and i cc (max) = 6 ma. by using equation 1 the largest possible amount of dissipated power is: p d = v in i in p d = 3.3 v 6 ma = 19.8 mw then, by rearranging equation 3: t a (max) = t j (max) C t t a (max) = 165c/w C (19.8 mw 145c/w) t a (max) = 165c/w C 2.9c = 162.1c ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
21 package outline drawing for reference only ? not for t ooling use (reference mo-153 aa) dimensions in millimeters - not to scale dimensions exclusive of mol d? ash, gate burrs, and dambar protrusions exact case and lead con?guration at supplier discretion within limits shown 3.00 0.10 1.50 6.40 bsc 6.40 bsc 4.40 0.10 1.38 1.63 1.70 0.45 0.65 e2 e1 d d b b c c e e d d d d 1 1 2 2 8 8 branded face 8x 0.10 c 0.30 0.19 0.65 bsc 0.25 bsc 0.15 0.05 1.10 max sea ting plane c 8o 0o 0.02 0.09 0.60 1.00 ref +0.15 -0.10 sea ting plane gauge plane pcb layout reference v iew standard branding reference v iew 1 nnn yyww a a = last 3 digits of device part number = supplier emblem = last two digits of year of manufactur e = w eek of manufactur e n y w te rminal #1 mark area reference land pattern layout (reference ipc7351 sop65p640x1 10-8m); all pads minimum of 0.20 mm from all adjacent pads; adjust as necessar y to meet application process requirements and pcb layout tolerances; when mounting on a multilayer pcb, thermal vias can improve thermal dissipatio n (reference eia/jedec standard jesd51-5) branding scale and appearance at supplier discretio n hall elements (e1 and e2), not to scal e activea rea depth = 0.36 mm ref figure 13: package le, 8-pin tssop ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
22 for the latest version of this document, visit our website: www.allegromicro.com revision history revision revision date description of revision C december 10, 2014 initial release 1 september 21, 2015 added aec q100 qualification under features and benefits copyright ?2015, allegro microsystems, llc allegro microsystems, llc 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. allegros products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of allegros product can reasonably be expected to cause bodily harm. the information included herein is believed to be accurate and reliable. however, allegro microsystems, llc assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use. ultra-sensitive, hall-effect speed and direction sensor with tpos A1232 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com

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