View AD22151_955271.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

rev. 0 information furnished by analog devices is believed to be accurate and reliable. however, no responsibility is assumed by analog devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. no license is granted by implication or otherwise under any patent or patent rights of analog devices. a AD22151 one technology way, p.o. box 9106, norwood, ma 02062-9106, u.s.a. tel: 781/329-4700 world wide web site: http://www.analog.com fax: 781/326-8703 ? analog devices, inc., 1997 linear output magnetic field sensor functional block diagram temp ref i source demod switches out amp ref v cc /2 AD22151 features adjustable offset to unipolar or bipolar operation low offset drift over temperature range gain adjustable over wide range low gain drift over temperature range adjustable first order temperature compensation ratiometric to v cc applications automotive throttle position sensing pedal position sensing suspension position sensing valve position sensing industrial absolute position sensing proximity sensing general description the AD22151 is a linear magnetic field transducer. the sensor output is a voltage proportional to a magnetic field applied perpendicularly to the package top surface. the sensor combines integrated bulk hall cell technology and instrumentation circuitry to minimize temperature related drifts associated with silicon hall cell characteristics. the architecture maximizes the advantages of a monolithic implementation while allowing sufficient versatility to meet varied application require- ments with a minimum number of components. principle features include dynamic offset drift cancellation and a built-in temperature sensor. designed for single +5 volt supply operation, the AD22151 achieves low drift offset and gain op- eration over ?0 c to +150 c. temperature compensation can accommodate a number of magnetic materials commonly uti- lized in economic position sensor assemblies. the transducer may be configured for specific signal gains de- pendent upon application requirements. output voltage can be adjusted from fully bipolar (reversible) field operation to fully unipolar field sensing. the voltage output achieves near rail-to-rail dynamic range, capable of supplying 1 ma into large capacitive loads. the sig- nal is ratiometric to the positive supply rail in all configurations. nc r1 gnd r3 r2 v cc AD22151 nc = no connect output 0.1 f figure 1. typical bipolar configuration with low (< C500 ppm) compensation nc r1 gnd r3 r2 v cc AD22151 nc = no connect output 0.1 f r4 "
- $ .
&
( C2000 ppm) compensation
C2C rev. 0 AD22151?pecifications (t a = +25 c and v+ = +5 v unless otherwise noted) parameters min typ max units operation v cc operating 4.5 5.0 6.0 v i cc operating 6.0 10 ma input tc3 (pin 3) sensitivity/volt 160 v/g/v input range 1 v cc 2 0.5 v output 2 sensitivity (external adjustment, gain = 1) 0.4 mv/g linear output range 10 90 % of v cc output min 5 % of v cc output max (clamp) 93 % of v cc drive capability 1.0 ma offset @ 0 gauss v cc 2 v offset adjust range 5 95 % of v cc output short circuit current 5.0 ma accuracies nonlinearity (10% to 90% range) 0.1 % fs gain error (over temperature range) 1% offset error (over temperature range) 6.0 g uncompensated gain tc (g tcu ) 950 ppm ratiometricity error 1 %v/v cc 3 db roll-off (5 mv/g) 5.7 khz output noise figure (6 khz bw) 2.4 mv/rms package 8-lead soic operating temperature range 40 +150 c notes 1 40 c to +150 c. 2 r l = 4.7 k ? . specifications subject to change without notice. caution esd (electrostatic discharge) sensitive device. electrostatic charges as high as 4000 v readily accumulate on the human body and test equipment and can discharge without detection. although the AD22151 features proprietary esd protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. therefore, proper esd precautions are recommended to avoid performance degradation or loss of functionality. absolute maximum rating* supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 v package power dissipation . . . . . . . . . . . . . . . . . . . . . 25 mw storage temperature . . . . . . . . . . . . . . . . . . 50 c to +160 c output sink current, i o . . . . . . . . . . . . . . . . . . . . . . . 15 ma magnetic flux density . . . . . . . . . . . . . . . . . . . . . . unlimited lead temperature (soldering 10 sec) . . . . . . . . . . . . . +300 c *stresses above those listed under absolute maximum ratings may cause perma- nent damage to the device. this is a stress rating only; the functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. exposure to the absolute maximum rating conditions for extended periods may affect device reliability. ordering guide temperature package package model range description option AD22151yr 40 c to +150 c 8-lead soic so-8 warning! esd sensitive device
AD22151 C3C rev. 0 pin configuration top view (not to scale) 8 7 6 5 1 2 3 4 area of sensitivity* tc1 tc2 tc3 gnd v cc ref gain output AD22151 (not to scale) 8 7 6 5 1 2 3 4 * shaded area represents magnetic field area of sensitivity (20mils 20mils) positive b field into top of package results in a positive voltage response pin function descriptions pin no. description connection 1 temperature compensation 1 output 2 temperature compensation 2 output 3 temperature compensation 3 input/output 4 ground 5 output output 6 gain input 7 reference output 8 positive power supply circuit operation the AD22151 consists of epi hall plate structures located at the center of the die. the hall plates are orthogonally sampled by commutation switches via a differential amplifier. the two amplified hall signals are synchronously demodulated to pro- vide a resultant offset cancellation (see figure 3). the demodu- lated signal passes through a noninverting amplifier to provide final gain and drive capability. the frequency at which the output signal is refreshed is 50 khz. temperature c 0.005 0.004 140 40 120 offset volts 100 80 60 40 20 0 20 0.004 0 0.001 0.002 0.003 0.003 0.001 0.002 figure 3. relative quiescent offset vs. temperature temperature dependencies the uncompensated gain temperature coefficient (g tcu ) of the AD22151 is the result of fundamental physical properties asso- ciated with silicon bulk hall plate structures. low doped hall plates operated in current bias mode exhibit a temperature relationship determined by the action of scattering mechanisms and doping concentration. the relative value of sensitivity to magnetic field can be altered by the application of mechanical force upon silicon. the mecha- nism is principally the redistribution of electrons throughout the valleys of the silicon crystal. mechanical force on the sensor is attributable to package-induced stress. the package material acts to distort the encapsulated silicon altering the hall cell gain by 2% and g tcu by 200 ppm. figure 4 shows the typical g tcu characteristic of the AD22151. this is the observable alteration of gain with respect to tempera- ture with pin 3 (tc3) held at a constant 2.5 v (uncompensated). if a permanent magnet source used in conjunction with the sensor also displays an intrinsic tc (b tc ), it will require factor- ing into the total temperature compensation of the sensor assembly. figures 5 and 6 represent typical overall temperature/gain per- formance for a sensor and field combination (b tc = 200 ppm). figure 5 is the total drift in volts over a 40 c to +150 c tem- perature range with respect to applied field. figure 6 represents typical percentage gain variation from +25 c. figures 7 and 8 show similar data for a b tc = 2000 ppm. temperature c 14 4 40 % gain 10 60 110 160 12 4 2 0 2 10 6 8 6 figure 4. uncompensated gain variation (from +25 c) vs. temperature
AD22151 C4C rev. 0 field gauss 0.025 delta signal volts 0.020 0 0.015 0.005 0.010 600 400 200 0 200 400 600 figure 5. signal drift over temperature (C40 c to +150 c) vs. field (C200 ppm); +5 v supply temperature c 0.25 % gain 0.20 0 0.15 0.05 0.10 40 10 60 110 160 0.05 figure 6. gain variation from +25 c vs. temperature (C200 ppm) field; r1 C15 k ? field gauss 0.045 delta signal volts 0.040 0 0.035 0.025 0.030 800 400 200 0 200 400 600 0.020 0.015 0.010 0.005 600 800 figure 7. signal drift over temperature (C40 c to +150 c) vs. field (C2000 ppm); +5 v supply temperature c 2.0 1.8 1.0 1.6 1.2 1.4 40 10 60 110 160 0.2 0.8 0.6 0.4 0.2 0 % gain figure 8. gain variation (from +25 c) vs. temperature (C2000 ppm field; r1 = 12 k ? ) temperature compensation the AD22151 incorporates a thermistor transducer that detects relative chip temperature within the package. this func tion provides a compensation mechanism for the various temperature dependencies of the hall cell and magnet combina- tions. the temperature information is accessible at pins 1 and 2 ( +2900 ppm / c) and pin 3 ( 2900 ppm/ c) as represented by figure 9. the compensation voltages are trimmed to con- verge at v cc /2 at +25 c. pin 3 is internally connected to the negative tc voltage via an internal resistor (see functional block diagram). an external resistor connected between pin 3 and pins 1 or 2 will produce a potential division of the two comple- mentary tc voltages to provide optimal compensation. the aforementioned pin 3 internal resistor provides a secondary tc designed to reduce second order hall cell temperature sensitivity. temperature c 1.0 volts reference 0.8 0 0.6 0.2 0.4 150 112 74 2 40 0.2 0.4 0.6 0.8 1.0 36 tc1, tc2 volts tc3 volts figure 9. tc1, tc2 and tc3 with respect to reference vs. temperature the voltages present at pins 1, 2 and 3 are proportional to the supply voltage. the presence of the pin 2 internal resistor distinguishes the effective compensation ranges of pins 1 and 2 (see temperature configuration in figures 1 and 2, and typical resistor values in figures 10 and 11). variation occurs in the operation of the gain temperature compensation for two reasons. first, the die temperature within
AD22151 C5C rev. 0 the package is somewhat higher than the ambient temperature due to self-heating as a function of power dissipation. second, package stress effect alters the specific operating parameters of the gain compensation, particularly the specific cross over temperature of tc1, tc3 ( 10 c). configuration and component selection there are three areas of sensor operation that require external component selection. temperature compensation (r1), signal gain (r2 and r3), and offset (r4). temperature if the internal gain compensation is used, an external resistor is required to complete the gain tc circuit at pin 3. a number of factors contribute to the value of this resistor. a. the intrinsic hall cell sensitivity tc 950 ppm. b. package induced stress variation in a. 150 ppm. c. specific field tc 200 ppm (alnico), 2000 ppm (ferrite), 0 ppm (electromagnet) etc. d. r1, tc. the final value of target compensation also dictates the use of either pin 1 or pin 2. pin 1 is provided to allow for large nega- tive field tc such as ferrite magnets, thus r1 would be con- nected to pins 1 and 3. pin 2 uses an internal resistive tc to optimize smaller field coefficients such as alnico, down to 0 ppm coefficients when only the sensor gain tc itself is dominant. the tc of r1 itself will also effect the compensation and as such a low tc resistor ( 50 ppm) is recommended. figures 10 and 11 indicate r1 resistor values and their associ- ated effectiveness for pins 1 and 2 respectively. note that the indicated drift response in both cases incorporates the intrinsic hall sensitivity tc (b tcu ). for example, the AD22151 sensor is to be used in conjunction with an alnico material permanent magnet. the tc of such magnets is 200 ppm (see figures 5 and 6). figure 11 indi- cates that a compensating drift of +200 ppm at pin 3 requires a nominal value of r1 = 18 k ? (assuming negligible drift of r1 itself). r1 k 3500 drift ppm 3000 1000 2500 1500 2000 0 5 10 20 25 500 0 15 30 figure 10. typical resistor value r1 vs. (pins 1 and 3) drift compensation r1 k 800 drift ppm 600 200 400 0 200 0 5 10 20 25 400 600 15 30 35 40 45 50 "
## $
#(=-/,
& gain and offset the operation of the AD22151 can be bipolar (i.e., 0 gauss = v cc /2) or a ratiometric offset can be implemented to position zero gauss point at some other potential (i.e., 0.25 v). the gain of the sensor can be set by the appropriate r2 and r3 resistor values (see figure 1) such that: gain = 1 + r 3 r 2 0. 4 mv / g (1) however, if an offset is required to position the quiescent out- put at some other voltage then the gain relationship is modified to: gain = 1 + r 3 ( r 2 r 4) 0. 4 mv / g (2) the offset that r4 introduces is: offset = r 3 ( r 3 + r 4) v cc v out () (3) for example: at v cc = 5 v at room temperature, the internal gain of the sensor is approximately 0.4 mv/gauss. if a sensitivity of 6 mv/ gauss is required with a quiescent output voltage of 1 v, the following calculations apply (see figure 2 ). a value for r3 would be selected that complied with the various considerations of current and power dissipation, trim ranges (if applicable), etc. for the purpose of example assume a value of 85 k ? . to achieve a quiescent offset of 1 v requires a value for r4 as: v cc 2 ? ? ? ? ? ? 1 v cc 1 = 0.375 (4) thus: r 4 = 85 k ? 0.375 ? ? ? ? ? ? 85 k ?= 141.666 k ? (5) the gain required would be 6/0.4 (mv/gauss) = 15
AD22151 C6C rev. 0 knowing the values of r3 and r4 from above, and noting equa- tion 2, the parallel combination of r2 and r4 required is: 85 k ? 15 1 () = 6.071 k ? thus: r 2 = 1 1 6.071 k ? ? ? ? ? ? ? 1 141.666 k ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? = 6.342 k ? noise the principle noise component in the sensor is thermal noise from the hall cell. clock feedthrough into the output signal is largely suppressed with application of a supply bypass capacitor. figure 12 shows the power spectral density (psd) of the output signal for a gain of 5 mv/gauss. the effective bandwidth of the sensor is approximately 5.7 khz. this is shown by figure 13 small signal bandwidth vs. gain. the psd indicates an rms noise voltage of 2.8 mv within the 3 db bandwidth of the sen- sor. a wideband measurement of 250 mhz indicates 3.2 mv rms (see figure 14a). in many position sensing applications bandwidth requirements can be as low as 100 hz. passing the output signal through an lp filter, for example 100 hz, would reduce the rms noise volt- age to 1 mv. a dominant pole may be introduced into the output amplifier response by connection of a capacitor across feedback resistor r3, as a simple means of reducing noise at the expense of bandwidth. figure 14b indicates the output signal of a 5 mv/g sensor bandwidth limited to 180 hz with a 0.01 f feedback capacitor. note: measurements taken with 0.1 f decoupling capacitor between v cc and gnd at +25 c. logmag 5 db /div 100 h 1 h start: 64 hz noise: psd ( 8 mv/gauss ) stop: 25.6 khz rms: 64 b marker x 64hz y: 3.351 h figure 12. power spectral density (5 mv/g) 3db freq. (khz) gain mv/gauss 7 frequency khz 6 2 5 3 4 12 3 1 0 456 figure 13. small-signal gain bandwidth ch2 10.0mv b w m2.00ms 2 tek stop: 25.0 ks/s [ [ t 3acqs t ch2 pk-pk 19.2mv figure 14a. peak-to-peak full bandwidth (10 mv/division) ch2 10.0mv b w m2.00ms 2 tek stop: 25.0 ks/s [ [ t 7acqs t ch2 pk-pk 4.4mv figure 14b. peak-to-peak 180 hz bandwidth (10 mv/division)
AD22151 C7C rev. 0 temperature c 2.496 volts 2.494 2.492 2.488 2.490 140 120 100 80 60 40 20 2.486 2.484 0 40 20 gain = 3.78mv/g "
#7 1 $

field gauss 0.06 0.05 0.04 0.02 0.03 600 400 200 0 200 400 600 0.01 0 0.01 0.02 0.03 0.04 0.05 % error figure 15. integral nonlinearity vs. field
AD22151 C8C rev. 0 outline dimensions dimensions shown in inches and (mm). c3213C8C10/97 printed in u.s.a. 8-lead soic (so-8) 0.0098 (0.25) 0.0075 (0.19) 0.0500 (1.27) 0.0160 (0.41) 8 0 0.0196 (0.50) 0.0099 (0.25) 45 85 4 1 0.1968 (5.00) 0.1890 (4.80) 0.2440 (6.20) 0.2284 (5.80) pin 1 0.1574 (4.00) 0.1497 (3.80) 0.0500 (1.27) bsc 0.0688 (1.75) 0.0532 (1.35) seating plane 0.0098 (0.25) 0.0040 (0.10) 0.0192 (0.49) 0.0138 (0.35)

▲Up To Search▲

Price & Availability of AD22151

	To Download AD22151 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .