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the a1698 is a hall-effect-based integrated circuit (ic) that provides a user-friendly solution for two-wire speed sensing of ring magnets or ferrous targets (when back-biased by the user) down to zero-speed in applications where speed and direction is required. the a1698 is offered in the ub package, which integrates the ic and a high temperature ceramic capacitor in a single overmolded sip package. the integrated capacitor provides enhanced emc performance. the integrated circuit incorporates hall-effect circuits and signal processing that switches in response to differential magnetic signals created by magnetic encoders, or, when properly back- biased with a magnet, from ferromagnetic targets. the circuitry contains a sophisticated digital circuit that reduces magnet and system offsets, calibrates the gain for air gap independent switchpoints, and provides true zero-speed operation. the regulated current output is configured for two-wire interface circuitry and is ideally suited for obtaining speed and direction information in wheel speed applications. the 2-pin sip package is lead (pb) free, with tin leadframe plating. a1698-ds, rev. 2 ? integrated capacitor for emc suppression in a single overmolded miniature package ? wide leads facilitate ease of assembly ? true zero-speed operation ? pulse-width output protocol ? automatic gain control (agc) for air gap independent switchpoints ? automatic offset adjustment (aoa) for signal processing optimization, providing large operating air gap range ? single chip sensing ic for high reliability ? fully synchronous digital logic with scan and iddq testing two-wire, true zero-speed, high accuracy sensor ic with speed and direction output functional block diagram a1698 supply ground amp amp filter filter output control offset adjust gain adjust digital controller chopper stabilization internal regulator adc adc offset adjust gain adjust 2 1 features and benefits description package: 2-pin sip (suffix ub) not to scale
2 selection guide part number temperature coefficient air gap warning and standstill function a1698lubtn-fwpe-t ring magnet yes A1698LUBTN-FWPG-T back-biased yes a1698lubtn-fwbe-t ring magnet no a1698lubtn-fwbg-t back-biased no temperature coef?cient: standstill pulses: con?guration options a1698 lu bt n- -t pulse widths: n?forward = 45 s (narrow) or w?forward = 90 s (wide) rotation direction: f?pin 1 to pin 2 forward or r?pin 2 to pin 1 forward e?ring magnet (0.2%/oc typ.) or g?back-biased b?blanked, no output during standstill, or p? pulses during standstill with warning pulses tn ?t ape and reel ub?2-pin plastic sip l a1698 leadframe plating instructions (packing) package designation operating temperature range: allegro identi?er and device type two-wire, true zero-speed, high accuracy sensor ic with speed and direction output a1698 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
3 ub package, 2-pin sip pinout diagram absolute maximum ratings characteristic symbol notes rating unit supply voltage v cc 28 v reverse supply voltage v rcc C18 v operating ambient temperature t a l temperature range C40 to 150 c maximum junction temperature t j(max) 165 c storage temperature t stg C65 to 170 c terminal list table name number function vcc 1 supply voltage gnd 2 ground internal discrete capacitor ratings characteristic symbol test conditions value (typ.) unit nominal capacitance c supply connected between vcc and gnd 2200 pf 21 specifications two-wire, true zero-speed, high accuracy sensor ic with speed and direction output a1698 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
4 characteristic symbol test conditions min. typ. 1 max. unit electrical characteristics supply voltage 2 v cc operating, t j < t j(max) 4 C 24 v reverse supply current 3 i rcc v cc = v rcc(max) C C C10 ma supply zener clamp voltage v zsupply i cc = i cc(max) + 3 ma, t a = 25c 28 C C v output power-on state i cc(low) C supply current i cc(low) low-current state 5.9 7 8.4 ma i cc(high) high-current state 12 14 16 ma supply current ratio i cc(high) / i cc(low) measured as ratio of high current to low current (isothermal) 1.9 C C C supply current stabilization time signal stabilization time from v cc > undervoltage lockout level C C 1 ms output rise/fall time t r , t f voltage measured at terminal 2 in figure 1, r l = 100 , c l = 10 pf, measured between 10% and 90% of signal. 0 C 1.5 s operating characteristics operate point b op % of peak-to-peak ic-processed magnetic signal C 60 C % release point b rp % of peak-to-peak ic-processed magnetic signal C 40 C % operating frequency f 0 C 5 khz input signal b sig differential signal, measured peak to peak 20 C 1200 g air gap warning b warn -p variant C 2 b sig(min) C g allowable user-induced differential offset b sigext external differential signal bias (dc), operating within specification C300 C 300 g sensitivity temperature coefficient 5 t c valid for full temperature range e variant, ring magnet C +0.2 C %/c g variant, back-biased C tbd C %/c total pitch deviation for constant b sig , sine wave C C +/-2 % front-end chopping frequency C 340 C khz output pulse characteristics, pulse protocol 4 pulse width off time t w(pre) 38 45 52 s pulse width, air gap warning t w(warn) -p variant 38 45 52 s pulse width, forward rotation t w(fwd) -n variant 38 45 52 s -w variant 76 90 104 s pulse width, reverse rotation t w(rev) -n variant 76 90 104 s -w variant 153 180 207 s pulse width, standstill t w(stop) -p variant 1232 1440 1656 s standstill period t stop -p variant 590 737 848 ms 1 typical values are at t a = 25c and v cc = 12 v. performance may vary for individual units, within the specifed maximum and minimum limits. 2 maximum voltage must be adjusted for power dissipation and junction temperature; see representative discussions in power derating section. 3 negative current is defned as conventional current coming out of (sourced from) the specifed device terminal. 4 load circuit is r l = 100 ? and c l = 10 pf. pulse duration measured at threshold of ( (i cc(high) + i cc(low) ) /2). 5 ring magnet decreases strength with rising temperature. device compensates. note that b sig requirement is not infuenced by this. operating characteristics : valid throughout full operating and temperature ranges, unless otherwise specifed two-wire, true zero-speed, high accuracy sensor ic with speed and direction output a1698 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
5 b seq(n) b seq(n+1) figure 2: differential signal variation figure 1: typical application circuit v supply c supply c l r l 100 1 2 a1698 target s n s n t target t target t vproc v proc v proc = the processed analog signal of the sinusoidal magnetic input (per channel) = the period between successive sensed target magnetic edges of the same polarity (either both north-to-south or both south-to-north) figure 3: defnition of t target two-wire, true zero-speed, high accuracy sensor ic with speed and direction output a1698 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
6 thermal characteristics characteristic symbol test conditions* value unit package thermal resistance r ja single-layer pcb with copper limited to solder pads 213 c/w *additional thermal information is available on the allegro website. 20 40 60 80 100 120 140 160 180 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 temperature (oc) maximum allowable v (v) cc v cc(max) v cc(min) power derating curve 20 40 60 80 100 120 140 160 180 100 0 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 temperature (oc) power dissipation p (mw) d power dissipation versus ambient temperature two-wire, true zero-speed, high accuracy sensor ic with speed and direction output a1698 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
7 characteristic plots v: 24 v cc v cc : 24 v 8.4 7.9 7.4 6.9 6.4 5.9 -50 0 50 100 150 t (oc) a i (ma) cc supply current versus ambient temperature v: 24 v cc v cc : 24 v 16.0 15.0 14.0 13.5 13.0 12.0 -50 0 50 100 150 t (oc) a i (ma) cc 15.5 14.5 12.5 supply current versus ambient temperature t w(fwd) , -w variant 104 92 88 84 -50 0 50 100 150 t (oc) a pulse width (s) 100 96 80 76 output pulse widths versus ambient temperature t w(fwd) , -w variant 207 195 183 177 171 153 -50 0 50 100 150 t (oc) a pulse width (s) 201 189 165 159 output pulse widths versus ambient temperature two-wire, true zero-speed, high accuracy sensor ic with speed and direction output a1698 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
8 functional description the sensor ic contains a single-chip hall-effect circuit that supports a trio of hall elements. these elements are used in differential pairs to provide electrical signals containing informa- tion regarding edge position and direction of target rotation. the a1698 is intended for use with ring magnet targets, or, when back-biased with an appropriate magnet, with ferromagnetic targets (gears). the ic detects the peaks of the magnetic signals and sets dynamic thresholds based on these detected signals. data protocol description when a target passes in front of the device (opposite the branded face of the package case), the a1698 generates an output pulse for each magnetic pole, or each tooth and valley, of the target. speed information is provided by the output pulse rate, while direction of target rotation is provided by the duration of the output pulses. the sensor ic can sense target movement in both the forward and reverse directions. the translation of magnetic input to the output is shown in figure 6. forward rotation for the Cf variant, when the target is rotating such that a target feature passes from pin 1 to pin 2, this is referred to as forward rotation. this direction of rotation is indicated on the output by a t w(fwd) pulse width. for the Cr variant, forward direction is indicated for target rotation from pin 2 to 1 (see figure 4). reverse rotation for the Cf variant, when the target is rotating such that a target feature passes from pin 2 to pin 1, this is referred to as reverse rotation. this direction of rotation is indicated on the output by a t w(rev) pulse width. for the Cr variant, reverse direction is indicated for target rotation from pin 1 to 2. output edges are triggered by v proc transitions through the switchpoints. on a crossing, the output is first set to i cc(low) for a duration of t w(pre) , after which the output pulse of i cc(high) is present for t w(fwd) or t w(rev) . the ic is always capable of properly detecting input signals up to the defined operating frequency. however, the end user will note that a sequence of t w(pre) and t w(rev) does meet this frequency. the t w(pre) period is dominant, thus always providing rising output edge, but, at high frequencies, potentially truncating the i cc(high) duration. figure 4: target orientation relative to device (ring magnet shown). n n n s n s s s n n n s n s s s rotation from pin 1 to pin 2 pin 1 pin 2 branded face of package rotatin (ring magnet or ferromagnetic) (ring magnet or ferromagnetic) g target rotation from pin 2 to pin 1 pin 1 pin 2 branded face of package rotating target figure 5: output timing example s n t w(fwd) t w(fwd) t w(pre) t w(pre) i cc(low) i cc(high) two-wire, true zero-speed, high accuracy sensor ic with speed and direction output a1698 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
9 b op b op b rp b rp device orientation to target package case branded face target magnetic pro?le +b ?b mechanical position (target moves past device pin 1 to pin 2) target (radial ring magnet) ic internal differential analog signals, v proc detected channel switching output (pulse protocol) (pin 2 side) (pin 1 side) (top vi ew of package case) ic this pole sensed later this pole sensed earlier n ss speed channel element pitch speed channel channel a direction channel channel b package case branded face (pin 2 side) (pin 1 side) (top vi ew of package case) back-biasing magnet speed channel element pitch this tooth sensed earlier this tooth sensed later device orientation to target mechanical position (target moves past device pin 1 to pin 2) target (gear) +b target magnetic pro?le ic south pole north pole b op b op b rp b rp ic internal differential analog signals, v proc detected channel switching output (pulse protocol) speed channel channel a direction channel channel b figure 6: basic operation two-wire, true zero-speed, high accuracy sensor ic with speed and direction output a1698 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
10 calibration and direction validation when power is applied to the a1698, the sensor ic internally detects the profile of the target. the gain and offset of the detected signals are adjusted during the calibration period, normalizing the internal signal amplitude for the installation air gap of the device. the automatic gain control (agc) feature ensures that opera- tional characteristics are isolated from the effects of installation air gap variation. automatic offset adjustment (aoa) is circuitry that compen- sates for the effects of chip, magnet, and installation offsets. this circuitry works with the agc during calibration to adjust v proc in the internal a-to-d range to allow for acquisition of signal peaks. aoa and agc function separately on the two differential signal channels. during calibration, output pulses with direction information are immediately transmitted to the output. depending on target design, air gap, and the phase of the target, direction may be momentarily incorrect. following a direction change in running mode, direction changes are immediately transmitted to the output. depending on target design and the phase of the target, direction may be fleetingly incorrect. target rotation ss nn ss nn n to r w(fwd) w(rev) t t w(fwd) t w(fwd) t w(fwd) to r w(fwd) w(rev) t target differential magnetic pro?le t opposite north pole opposite south pole opposite ns boundary opposite sn boundary i cc device location at power-on figure 7: startup position effect on first device output switching normal target rotation normal target rotation s s s nn s s n nn t w(fwd) t w(fwd) t w(fwd) t w(rev) t w(fwd) [or ]t w(rev) [or ]t w(rev) t/ w(fwd) w(rev) t target dif ferential magnetic pro?le vibration [or ]t w(rev) [or ]t w(fwd) [or ]t w(rev) figure 8: output functionality in the presence of running mode target vibration two-wire, true zero-speed, high accuracy sensor ic with speed and direction output a1698 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
11 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 supplied 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 website.) 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 = 14 ma, and r ja = 213 c/w, then: p d = v cc i cc = 12 v 7 ma = 84 mw t = p d r ja = 84 mw 213 c/w = 17.9c t j = t a + t = 25c + 17.9c = 42.9c 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 ub, using minimum-k pcb. observe the worst-case ratings for the device, specifically: r ja = 213c/w, t j(max) = 165c, v cc(max) = 24 v, and i cc(avg) = 14.66 ma. i cc(avg) is computed using i cc(high)(max) and i cc(low)(max) , with a duty cycle of 73% computed from t w(rev)(max) on-time and t w(fw)(min) off-time (pulse width proto- col). this condition happens at a select limiting frequency. calculate the maximum allowable power level (p d(max) ). first, invert equation 3: t max = t j(max) C t a = 165 c 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 213 c/w = 70.4 mw finally , invert equation 1 with respect to voltage: v cc(est) = p d(max) i cc(avg) = 70.4 mw 14.6 ma = 4.8 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 reliable 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. power derating two-wire, true zero-speed, high accuracy sensor ic with speed and direction output a1698 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
12 figure 9: package ub, 2-pin sip for reference only ?n ot for tooling use (reference dwg-9070) dimensions in millimeters ? not to scale dimensions exclusive of mol d? ash, gate burs, and dambar protrusions exact case and lead con?guration at supplier discretion within limits shown mold ejector pin indent a b c d e f dambar removal protrusion (8) gate and tie burr area hall elements (e1, e2, and e3); not to scale molded lead bar for preventing damage to leads during shipment active area depth, 0.38 mm ref branding scale and appearance at supplier discretion 0.25 ref 0.30 ref 4 x 2.50 ref 4 x 7.37 ref 4 x 0.85 ref 4 x 0.85 ref 0.38 ref 0.25 ref 45 0.85 0.05 0.85 0.05 2 1 b 4x10 a branded face 0.25 +0.05 ?0.03 0.42 0.10 4.00 0.05 4.00 0.05 4.00 0.05 1.00 0.10 1.80 ref 2.54 ref 12.20 0.10 1.80 0.05 1.50 0.10 1.50 0.10 c f e1 e3 e2 1.45 1.45 e e e e e 0.55 e 1.41 e d = supplier emblem = last three digits of device part number = last 2 digits of year of manufacture = week of manufacture = lot number n y w l standard branding reference vi ew yyww llll nnn package outline drawing two-wire, true zero-speed, high accuracy sensor ic with speed and direction output a1698 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com
13 revision history revision current revision date description of revision C march 24, 2015 initial release. 1 may 6, 2015 corrected typo in selection guide. 2 march 2, 2016 updated package outline drawing molded lead bar footnote, internal discrete capacitor ratings table, and miscellaneous editorial changes. for the latest version of this document, visit our website: www.allegromicro.com copyright ?2016, 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. two-wire, true zero-speed, high accuracy sensor ic with speed and direction output a1698 allegro microsystems, llc 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com

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