Honeywell 1- 2-Axis Magnetic Sensors HMC1001 1002 HMC1021 1022 handbook
Contents
1. LINEAR MAGNETIC FIELD SENSORS Simple Circuit Application The circuit in Figure 16 shows a simple application of a magnetic sensor This circuit acts as a proximity sensor and will turn on the LED when a magnetis brought within 0 25 to 0 5 inch of the sensor The amplifier acts as a simple comparator and switches low when the HMC 1001 bridge output exceeds 30mV The magnet must be magnet movement mm C Magnetic Magnetic Sensor 45V 45V Sensor 45V i 0 154 Ff 12 uu 3 B LED 9 5 400 e 6 m I Vout T lt Gain 1000 BW 10Hz WEE R1 is used to trim switchpoint provides 10Hz rolloff 3 1 Calibrate 1 Trim R1 for V V 30mV 2 Apply signal 30mV LED should be off 3 Apply signal 30mV LED should be on S R Pulse Figure 16 Magnetic Proximity Switch 0 01 eh Vref 22 1K r ES R3 10 l5 mA VW CS5509 16 bit A D Va 61113 Ain conv 14 x SCLK SDATA NDRDY H Ref XIN Ref CAL 3 Gnd Ncs H R1 or R2 used to trim offest provides 1KHz rolloff Magnetic Sensor 650 CS5509 1 5nF 16 bit A D 8 1 j Vi 6 11 13 ai E 8 o gt 6 Vout 7 Aime conv 2 T 7 AMPO4 E SCLK V SDATA 25K iet NDRDY H re Ref XINH gm LM440 19 Ref CALI amp 3 1 2 5V Gnd LL WZ SG NCS R1 or R2 used to trim offest R3 4510 for 1 axis 9210 for 2 axis or 14110 for 3 a2. the current flow and the magnetization vector During manufacture the easy axis preferred direction of magnetic field is set to one direction along the length of the film This allows the maximum change in resistance for an applied field within the permalloy film However the influence of a strong magnetic field more than 10 gauss along the easy axis could upset or flip the polarity of film magnetization thus changing the sensor characteristics Following such an upset field a strong restoring magnetic field must be applied momentarily to restore or set the sensor characteristics This effect will be referred to as applying a set pulse or reset pulse Polarity of the bridge output signal depends upon the direction of this internal film magnetization and is symmetric about the zero field output The OFFSET strap allows for several modes of operation when a dc current is driven through it An unwanted magnetic field can be subtracted out The bridge offset can be set to zero The bridge output can drive the OFFSET strap to cancel out the field being measured in a closed loop configuration The bridge gain can be auto calibrated in the system on command The Set Reset S R strap can be pulsed with a high current to Force the sensor to operate in the high sensitivity mode Flip the polarity of the output response curve Be cycled during normal operation to improve linearity and reduce cross axis effects and temperature effe
3. Circuit 1001 1002 0 022uF Clock e 10 5V Clock For any magnetic sensor application if temperature drift is notanissue thenthe reset pulse need only be occasionally applied This will save power and enable the use of digital filtering techniques as shown in Figure 12 Circumstances for a reset pulse would be 1 power on or 2 field over under range condition Any other time the sensor should perform normally 200 1uF 1 FMMT717 HMC1022 Clock FMMT617 1 Tantalum low R Figure 12 5V Circuit for SET RESET 1021 1022 The circuit in Figure 13 generates a strong set reset pulse under a microprocessor clock driven control A free running 555 timer can also be used to clock the circuit The SET current pulse is drawn from the 1 uF capacitor and a 200 ohm dropping resistor should be placed in series with the supply to reduce noise 10 LINEAR MAGNETIC FIELD SENSORS 200 1uF 1 4510 6V HF 1 5V m Clock 3 NU HMC1022 4 to14V 4 IRF7105 2 set DI9952 2 14 8 9 15 m TPW 2 usec O1gF Z E VW 5 6 reset 2 7 8 4 to 14V Clock h S R 1 1 Tantalum low R set rst set lt 2 Rds 0 2 ohm Figure 13 Set Reset Pulse With Clock Control 1021 1022 Low Power For low power application down to 3 3 volt supply the circuit shown in Figure 15 can be used These low threshold FETs provide low on
4. SET condition The bridge output can then be measured and stored as Vout set Another pulse of equal and opposite current should be driven through the S R pins to perform a RESET condi tion The bridge output can then be measured and stored as Vout reset The bridge output Vout can be expressed as Vout Vout set Vout reset 2 This technique cancels out offset and temperature effects introduced by the electron ics as well as the bridge temperature drift There are many ways to design the set reset pulsing circuit though budgets and ultimate field resolution will determine which approach will be best for a given application A simple set reset circuit is shown in Figure 5 6 9V 8 25K RESET SET RESET S 7 k Signal should be in m RESET state when idle 0 2uF x S R at 7 al 0 1uF 78 2 Signal input Manual Switch Figure 5 Single Axis Set Reset Pulse Circuit 1001 The magnitude of the set reset current pulse depends on the magnetic noise sensitivity of the system Ifthe minimum detectable field for a given application is roughly 500 ugauss in HMC1001 2 then a3 amp pulse min is adequate If the minimum detectable field is less than 100 ugauss then a 4 amp pulse min is required The circuit that generates the S R pulse should be located close to the MR sensor and have good power and ground connections The set reset straps on the Honeywell magnetic sensor
5. direction of applied field that generates a positive output voltage after a SET pulse LINEAR MAGNETIC FIELD SENSORS BASIC DEVICE OPERATION Honeywell magnetoresistive sensors are simple resistive bridge devices Figure 1 that only require a supply voltage to measure magnetic fields When a voltage from 0 to 10 volts is connected to Vbridge the sensor begins measuring any ambient or applied magnetic field in the sensitive axis In addition to the bridge circuit the sensor has two on chip magnetically coupled straps the OFFSET strap and the Set Reset strap These straps are patented by Honeywell and eliminate the need for external coils around the devices Vbridge 7 loffset gt 2 0 Q max UT S R S R 9 d Vi eq Iset lreset R 600 1200 Q Figure 1 On Chip components HMC1001 Magnetoresistive sensors are made of a nickel iron Permalloy thin film deposited on a silicon wafer and patterned as a resistive strip In the presence of an applied magnetic field a change in the bridge resistance causes a corresponding change in voltage output An external magnetic field applied normal to the side of the film causes the magnetization vector to rotate and change angle This in turn will cause the resistance value to vary AR R and produce a voltage output change in the Wheatstone bridge This change inthe Permalloy resistance is termed the magnetoresistive effectand is directly related to the angle of
6. resistance 0 3Q at Vas 2 7V The set reset pulsing does not need to be continuous To save power the SET pulse can be initially applied followed by a single RESET pulse The offset OS can be calculated as OS Vset Vrst 2 Vout Vrst OS OS Vset Vrst 2 This offset term will contain the DC offset of both the sensor bridge and interface electronics as well as the temperature drift of the bridge and interface electronics Store this value and subtract it from all future bridge output readings Once the bridge is RESET it will remain in that state for years or until a disturbing field gt 20 gauss is applied A timer can be set say every 10 minutes to periodically update the offset term A flow chart is shown in Figure 14 along witha timing diagram in Figure 15 to illustrate this process Read Vrst Figure 14 Low Power Set Rst Flowchart Ta Tb Ta Tc 9 mm Reset 200 1uF 1 43 3t0 d 6 5V r Set 1 3 NA d HMC1022 iE a Set ot E Vout read read 14 8 9 15 Vset Vrst 5 6 7 8 NDS9933 0 1pF NA I 5678 24 S R puce Reset 2R S R LIT 1 Tantalum low R 1 31 NDS8926 2 Rds 0 2 ohm Ta 5 usec Vp reset i Z Tb gt 1 usec Tc gt 20 usec 50 msec max TPW 2 usec Td gt 20 usec Vp gt 3V Figure 15 Single Clock Set Reset Pulse Circuit 1021 1022 11
7. 0 0 helo D D Honeywell SENSOR PRODUCTS APPLICATIONS 1 and 2 Axis Magnetic Compassing Navigation Systems Senso rs Attitude Reference HMC1 001 1 002 Traffic Detection HMC1 021 1 022 Medical Devices naso as a 4 element wheatstone bridge these magnetoresistive sensors convert magnetic fields to a differential output volt age capable of sensing magnetic fields as low as 30 ugauss These MRs offer a small low cost high sensitivity and high reliability solution for low field magnetic sensing Non Contact Switch Not actual size FEATURES AND BENEFITS Wide Field Range Field range up to 6 gauss earth s field 0 5 gauss Small Package Designed for 1 and 2 axis to work together to provide 3 axis x y z sensing 1 axis part in an 8 pin SIP or an 8 pin SOIC or a ceramic 8 pin DIP package 2 axis part in a 16 pin or 20 pin SOIC package Solid State These small devices reduce board assembly costs improve reliability and ruggedness com pared to mechanical fluxgates On Chip Coils Patented on chip set reset straps to reduce effects of temperature drift non linearity errors and loss of signal output due to the presence of high magnetic fields Patented on chip offset straps for elimination of the effects of hard iron distortion Cost Effective The sensors were specifically designed to be affordable for high volume OEM applications LINEAR MAGNETIC FIELD SENSORS HMC1001 1002 SPEC
8. AX662A R1 R4 used to trim offest C2 C1 Z 3t provides 1KHz rolloff O 22uF 0 22UF 4 1 C2 C1 5 Vcc 5V 4 7uF 19V S Vout SHDN 25 tantalum 1K ly 7 7v 4 74F Sir Sask T GND F Q 4 FN H 0 1uF O2uF E 0 1pF 7 8 2 SR o Signal input Rst Set Rst I 1 7 Signal should be in Rst EA state when idle Manual Switch Figure 20 Two Axis Sensor With Set Reset Circuit and Digital Interface 5V Vref lt 4 PEE v SUE A LM324a w F orur Magnetic Sensor Vb 2 5 LM324b Ww Vref Vb Sel ss Sel 2 5 LM324c NC Vref AB x O 1uF OX iq CE l o Output rel 2X M SiRstraps OF 3X 4052 Vref Vref e p SIR Control t5 LM324d NZ HMc1001 Vref v SiRstrap O 1uF Ea 200 5V NDC7001 or equiv Figure 21 Three Axis Low Cost Magnetic Sensor 13 LINEAR MAGNETIC FIELD SENSORS PACKAGE OUTLINES HMC1002 Package Outline mi D A1 20 1a E lt lt mM x 1l 10 ri HTT 8 a a u idet B HMC1001 8 Pin SIP and HMC1021Z 8 Pin SIP k o 1 ele B lt At HMC1021D 8 Pin Ceramic DIP ole la d r7 elg tee HMC1022 16 Pin SOIC Ik D j A1 Pitti fie 9 WM A H
9. E 1 E 3 i OI c ele 8 h x 45 Millimeters Inches Symbol Min Max Min Max A 2 489 2 642 098 104 A1 0 127 0 279 005 011 B 0 457 0 483 014 019 D 12 675 12 929 499 509 E 7 260 7 417 286 292 e 1 270 ref 050 ref H 1 270 10 566 396 416 h 0 381 ref 015 030 Millimeters Inches Symbol Min Max Min Max A 1 371 1 728 054 068 A1 0 101 0 249 004 010 B 0 355 0 483 014 019 D 9 829 11 253 387 443 E 3 810 3 988 150 157 e 1 270 ref 050 ref H 6 850 7 300 0 270 0 287 h 0 381 0 762 015 030 Millimeters Inches Symbol Min Max Min Max A 2 718 ref 0 107 ref A1 0 229 0 305 0 009 0 012 b 0 406 0 508 0 016 0 020 D 10 287 0 405 E 7 163 7 569 0 282 0 298 E1 7 366 7 874 0 290 0 310 e 2 54 ref 0 100 ref Q 0 381 1 524 0 015 0 060 L 3 175 4 445 0 125 0 175 Millimeters Inches Symbol Min Max Min Max A 1 371 1 728 054 068 A1 0 101 0 249 004 010 B 0 355 0 483 014 019 D 4 800 4 979 189 196 E 3 810 3 988 150 157 e 1 270 ref 050 ref H 5 816 6 198 229 244 h 0 381 0 762 015 030 Millimeters Inches Symbol Min Max Min Max A 1 371 1 728 054 068 A1 0 101 0 249 004 010 B 0 355 0 483 014 019 D 9 829 11 253 387 443 E 3 810 3 988 150 157 e 1 270 ref 050 ref H 5 816 6 198 229 244 h 0 381 0 762 015 030 14 LINEAR MAGNETIC FIELD SENSORS DESIGN PACKAGE OPTIONS Honeywell offe
10. IFICATIONS Characteristics Conditions Min Typ Max Unit Bridge Supply Vbridge referenced to GND 5 12 Volts Bridge Resistance Bridge current 10mA 600 850 1200 ohm Operating Temperature 4 55 150 C Storage Temperature 4 Unbiased 55 175 C Field Range 4 Full scale FS total applied field 2 2 gauss Linearity Error 4 Best fit straight line 1 gauss 0 1 0 5 FS 2 gauss 1 2 Hysteresis Error 4 3 sweeps across 2 gauss 0 05 0 10 FS Repeatability Error 4 3 sweeps across 2 gauss 0 05 0 10 FS S R Repeatability 1 10 S R Repeatability 2 Output variation after alternate S R pulses 2 100 uV Bridge Offset Offset OUT OUT Field 0 gauss 60 15 30 mV after Set pulse Vbridge 8V Sensitivity S R Current 3A 2 5 3 2 4 0 mV V gauss Noise Density 4 Noise at 1 Hz Vbridge 5V 29 nV Hz Resolution 4 Bandwidth 10Hz Vbridge 5V 27 ugauss Bandwidth 4 Magnetic signal lower limit 2 DC 5 MHz OFFSET Strap Measured from OFFSET to OFFSET 2 5 3 5 ohm OFFSET Strap Q Tempco 4 TA 40 to 125 C 0 39 9e C OFFSET Field 4 Field applied in sensitive direction 46 51 56 mA gauss Set Reset Strap Measured from S R to S R 1 5 1 8 ohm Set Reset Current 2 3 4 2 us current pulse 196 duty cycle 3 0 3 2 5 Amp Set Reset Q Tempco 4 T A 40 to 125 C 0 37 9e C Disturbing Field 4 Sensitivity starts to degrade 3 gauss Use S R pulse to restore sens
11. ck in the loop this will drive the MR bridge output to zero OUT OUT This method gives extremely good linearity and temperature characteristics The idea here is to always operate the MR bridge in the balanced resistance mode That is no matter what magnetic field is being measured the current through the OFFSET strap will cancel it out The bridge always sees a zero field condition The resultant current used to cancel the applied field is a direct measure of that field strength and can be translated into the field value The OFFSET strap can also be used to auto calibrate the MR bridge while in the application during normal operation This is useful for occasionally checking the bridge gain for that axis or to make adjustments over a large temperature swing This can be done during power up or anytime during normal operation The concept is simple take two point along a line and determine the slope of that line the gain When the bridge is measuring a steady applied magnetic field the output will remain constant Record the reading for the steady field and call it H1 Now apply a known current through the OFFSET strap and record that reading as H2 The current through the OFFSET strap will cause a change in the field the MR sensor measures call that delta applied field AHa The MR sensor gain is then computed as MRgain H2 H1 AHa There are many other uses forthe OFFSET strap than those described here The key point
12. cts The output response curves shown in Figure 2 illustrate the effects of the S R pulse When a SET current pulse Iset is driven into the SR pin the output response follow the curve with the positive slope When a RESET current pulse Ireset is driven into the SR pin the output response follow the curve with the negative slope These curves are mirror images about the origin except for two offset effects In the vertical direction the bridge offset shown in Figure 2 is around 25mV This is due to the resistor mismatch during the manufacture process This offset can be trimmedto zero by one of several techniques The most straight forward technique is to add a shunt parallel resistor across one leg ofthe bridge to force both outputs to the same voltage This must be done in a zero magnetic field environment usually in a zero gauss chamber The offset of Figure 2 in the horizontal direction is referred to hereasthe external offset This may be dueto anearby ferrous object or an unwanted magnetic field that is interfering with the applied field being measured A dc current in the OFFSET strap can adjust this offset to zero Other methods such as shielding the unwanted field can also be used to zero the external offset The output response curves due to the SET and RESET pulses are reflected about these two offsets Vec 8V 1001 1002 response after Iset response after Ireset bridge offset external offset Out
13. et Circuit With Microprocessor Control 1001 1002 LINEAR MAGNETIC FIELD SENSORS Low Field Measurements When measuring 100 ugauss resolution or less the permalloy film must be completely set or reset to insure low noise and repeatable measurements A current pulse of 4 amps or more for just a couple microseconds will ensure this The circuits in Figures 8 and 9 are recommended for applications of HMC1001 2 that require low noise and high sensitivity magnetic readings Low Cost For minimum field measurements above 500 ugauss a less elaborate pulsing circuit can be used In both Figures 10 and 11 the pulse signal is switched using lower cost Darlington transistors and fewer components This circuit may have a more limited temperature range depending on the quality of transistors selected If accuracy is not an issue and cost is then the reset only circuit in Figure 11 will work 16 to 20V 4 7uF 1 10K NV S R strap 4 50 typ 0 022uF 3A peak min zns HMC2003 0 22uF 17 1 0 022uF VW t ul o Clock o ZTX605 S R 10K 1 Tantalum low R NA Figure 10 Single Clock Set Reset Circuit 1001 1002 S R strap 4 50 typ 416 to 20V 3A peak min 100K HMC2003 0 22uF I e ZTX605 S R S R TPW 2 usec e iey reset The HMC2003 has 3 axis S R straps in series These are the HMC1001 and HMC1002 sensors Figure 11 Single Clock Reset Only
14. irection Figure 4B This will ensure a high sensitivity and repeatable reading A negative pulse Reset will rotate the magnetic domain orientation in the opposite direction Figure 4C and change the polarity of the sensor outputs The state of these magnetic domains can retain for years as long as there is no magnetic disturbing field present Permalloy NiFe Resistor Random Domain Orientations Fig 4A After a Set Pulse Fig 4B After a Reset Pulse Fig 4C Figure 4 The on chip S R should be pulsed with a current to realign or flip the magnetic domains in the sensor This pulse can be as short as two microsecond and on average consumes less than 1 mA dc when pulsing continuously The duty cycle can be selected for a 2 usec pulse every 50 msec or longer to conserve power The only requirement is that each pulse only drive in one direction That is ifa 3 5 amp pulse is used to set the sensor the pulse decay should not drop below zero current Any undershoot of the current pulse will tend to un set the sensor and the sensitivity will not be optimum Using the S R strap many effects can be eliminated or reduced that include temperature drift non linearity errors cross axis effects and loss of signal output due to the presence of a high magnetic fields This can be accom plished by the following process Acurrent pulse Iset can be driven from the S R to the S R pins to perform a
15. is that ambient field and the OFFSET field simply add to one another and are measured by the MR sensor as a single field LINEAR MAGNETIC FIELD SENSORS WHAT IS SET RESET STRAP Most low field magnetic sensors will be affected by large magnetic disturbing fields gt 4 20 gauss that may lead to output signal degradation In order to reduce this effect and maximize the signal output a magnetic switching technique can be applied to the MR bridge that eliminates the effect of past magnetic history The purpose of the Set Reset S R strap is to restore the MR sensor to its high sensitivity state for measuring magnetic fields This is done by pulsing a large current through the S R strap The Set Reset S R strap looks like a resistance between the SR and SR pins This strap differs from the OFFSET strap in that it is magnetically coupled to the MR sensor in the cross axis or insensitive direction Once the sensor is set or reset low noise and high sensitivity field measurement can occur In the discussion that follows the term set refers to either a set or reset current When MR sensors exposed to a magnetic disturbing field the sensor elements are broken up into ramdonly oriented magnetic domains Figure 4A that leads to sensitivity degrading A current pulse set with a peak current above minimum current in spec through the Set Reset strap will generate a strong magnetic field that realigns the magnetic domainsin one d
16. itivity Sensitivity Tempco 4 TA 40to 125 C Vbridge 8V 0 32 0 3 0 28 9e C Ibridge 5mA 0 06 Bridge Offset Tempco 4 TA 40to 125 C no Set Reset 0 03 C Vbridge 5V with Set Reset 0 001 Resistance Tempco 4 TA 40 to 125 C 0 25 I C Cross Axis Effect 4 Cross field21gauss no Set Reset 3 FS see AN 205 with Set Reset 0 5 Max Exposed Field 4 No perming effect on zero reading 10000 gauss Weight HMC1001 0 14 gram HMC1002 0 53 1 VBridge 4 3V Is R 3 2A VOUT VSET VRESET 2 If VBridge 8 0V Is R 2 0A lower S R current leads to greater output variation 4 Not tested in production guaranteed by characterization Tested at 25 C except otherwise stated Units 1 gauss g 1 Oersted in air 79 58 A m 1G 10E 4 Tesla 1G 10E5 gamma 3 Effective current from power supply is less than 1mA LINEAR MAGNETIC FIELD SENSORS HMC1021 1022 SPECIFICATIONS Characteristic Conditions Min Typ Max Unit Bridge Supply Vbridge referenced to GND 5 25 Volts Bridge Resistance Bridge current 5mA 800 1100 1300 Q Operating Temperature 1 HMC1021S 1021Z 1022 55 150 C HMC1021D 55 300 Storage Temperature 1 Unbiased 55 175 C Field Range 1 Full scale FS total applied field 6 6 gauss Best fit straight line 1 gauss 0 05 Linearity Error 1 3 gauss 0 4 FS 6 gauss 1 6 Hy
17. o set reset in this region Set Reset Voltage V LINEAR MAGNETIC FIELD SENSORS PACKAGE PINOUT SPECIFICATIONS HMC1002 Two Axis MR Microcircuit HMC1001 One Axis MR Microcircuit GND1 A 1 mm WW im 20 S R A FINA OUT A 2 mmi mm 19 NC S R 1 OFFSET A 3 wm C amp A ima 18 GND PLN OFFSET 2 Vbridge A 4 mmi im 17 OFFSET A S R 3 Die OUT A 5 mmi mm 16 S R A GND 4 mm GND2 A 6 BH imm 15 OFFSET B Out 5 S R B 7 mmi Em 14 S R B OFFSET 6 GND1 B 8 im 13 GND2 B Out B 9 wm im 12 OUT B VEHdges 7 OFFSET B 10 mm im 11 Vbridge B Out 8 m HMC1022 Two Axis MR Circuit HMC1021S One Axis MR Circuit OFFSET A 1 m o mmm 16 OFFSET A OUT A 2 mmm Dic A mmm 15 S R A OUT 1 m ie 8 OFFSET VBRIDGE A 3 wmm _ mmm 14 S R A VBRIDGE 2 m 7 OFFSET OUT A 4 mm mmm 13 GND B GND 3 mmm 6 S R OUT B 5 mmm mmm 12 OUT B OUT 4 m 5 S R VBRIDGE B 6 2 Lum 11 OFFSET B GND A 7 m t mmm 10 OFFSET B HMC1021S S R B 8 mmm m 9 S R B HMC1021D One Axis MR Circuit HMC1021Z One Axis MR Circuit OUT 1 Die 8 OFFSET OUT 1 m e VBRIDGE 2 7 OFFSET VBRIDGE 2 mmm GND 3 _ 6 S R a Die Te 4 mum ix ase S R 5 amm OFFSET 6 mm OFFSET 7 mmm OUT 8 mmm Arrow indicates
18. put Voltage mV Applied Field Gauss Figure 2 Ouiput Voltage vs Applied Magnetic Field LINEAR MAGNETIC FIELD SENSORS NOISE CHARACTERISTICS The noise density curve for a typical MR sensor is shown in Figure 3 The 1 f slope has a corner frequency near 10 Hz and flattens out to 3 8 nV VHz This is approximately equivalent to the Johnson noise or white noise for an 8500 resistor the typical bridge resistance To relate the noise density voltage in Figure 3to the magnetic fields use the following expressions For Vsupply 5V and Sensitivity 3 2mV V gauss Bridge output response 16 mV gauss Or 16 nV ugauss The noise density at 1Hz 30nV VHz and corresponds to 1 8 ugauss VHz For the noise components use the following expressions 1 f noise 0 1 10Hz 30 V In 10 1 nV 64 nV rms 4ugauss rms 27 ugauss p p 3 8 VBW nV 120 nV rms 50 ugauss p p white noise BW 1KHz 1000 1001 1002 100 Noise Density nV VHz 0 1 1 10 100 Frequency Hz 1000 Figure 3 Typical Noise Density Curve WHAT IS OFFSET STRAP Any ambient magnetic field can be canceled by driving a defined current through the OFFSET strap This is useful for eliminating the effects of stray hard iron distortion of the earth s magnetic field For example reducing the effects of a car body on the earth s magnetic field in an automotive compass application If the MR sensor has a fixed position wi
19. rs a range of magnetic microcircuit products Two axis parts contain two sensors for the x and y field Two different sensor designs and five package measurements Single axis variations include aSIP package configurations are available for mounting through the circuit board to create a 3 axis solution a SOIC for direct surface mount and a ceramic DIP HMC1001 1002 series offers a higher sensitivity and for high performance military and high temperature lower field resolution applications HMC1021 1022 series offers a wider field range lower set reset current and has a lower cost for higher volume applications HMC1001 02 HMC1021 22 Units Sensitivity 3 1 1 0 mV V G Resolution 27 85 ugauss Range t2 t6 gauss Set Rst Current 3 0 0 5 Amps Cost Lower in high volume ORDERING INFORMATION Part Number Axis Number Sensitivity Package Style HMC1001 Single 38mV V G 8 Pin SIP HMC1002 Two 38mV V G 20 Pin SOIC HMC1021D Single 1mV V G 8 Pin Ceramic DIP HMC1021Z Single 1mV V G 8 Pin SIP HMC1021S Single 1mV V G 8 Pin SOIC HMC1022 Two 1mV V G 16 Pin SOIC Solid State Electronics Center 12001 State Highway 55 Plymouth MN 55441 800 323 8295 www magneticsensors com Additional Product Details Customer Service Representative 612 954 2888 fax 612 954 2257 E Mail clr mn14 ssec honeywell com Honeywell reserves the right to make changes to any products or technolog
20. s are labeled S R and S R There is no polarity implied since this is simply a metal strap resistance LINEAR MAGNETIC FIELD SENSORS Single Clock Circuitry Some form of clock is needed to trigger the set and reset pulses Figure 6 to create the switching signal The circuit shown in Figure 8 can be used to create a strong gt 4Amp pulse The diodes resistors capacitors and inverters basically create the TRS and the TSR delays Now a single signal Clock can trigger a set or reset pulse The minimum timing between the rising and falling edges of Clock are determined by the 25KQ and 1nF time constant That is the minimum high and low time for Clock is 25 us Micro Processor The circuit in Figure 9 generates a strong set reset pulse gt 4 Amp under microprocessor control The 5V Clock TPW 2 usec S R 16v reset Figure 6 Single Clock Set Reset Timing SET and RESET signals are generated from a microprocessor and control the P and N channel HEXFET drivers IRF7105 The purpose of creating the TRS and the TSR delays are to make sure that one HEXFET is off before the other one turns on Basically a break before make switching pattern The current pulse is drawn from the 4 7 uF capacitor If the 5V to 20V converter is used as shown in Figure 7 then the resultant noise and droop on the 16 20V supply is not an issue But if the 16 20V supply is used elsewhere in the system
21. steresis Error 1 3 sweeps across 3 gauss 0 08 FS Repeatability Error 1 3 sweeps across 3 gauss 0 08 FS Bridge Offset Offset OUT OUT Field 0 gauss 10 2 5 11 25 mV After Set pulse Vbridge 5V Sensitivity S R Current 0 5A 0 8 1 0 1 25 mV V gauss Noise Density 1 Noise at 1Hz Vbridge 5V 48 nV VHz Resolution 1 Bandwidth 10Hz Vbridge 5V 85 ugauss Bandwidth 1 Magnetic signal lower limit DC 5 MHz OFFSET Strap Measured from OFFSET to OFFSET 38 50 60 Q OFFSET Strap Q Tempco 1 TA 40 to 125 C 0 39 I C OFFSET Field 1 Field applied in sensitive direction 4 0 4 6 6 0 mA gauss Set Reset Strap Measured from S R to S R 5 5 7 7 9 Q Set Reset Current 2us current pulse 1 duty cycle 0 5 0 5 4 0 Amp Set Reset O Tempco 1 TA 40 to 125 C 0 37 I C Disturbing Field 1 Sensitivity starts to degrade Use S R 20 gauss pulse to restore sensitivity Sensitivity Tempco 1 TA 40 to 125 C Vbridge 5V 0 32 0 3 0 28 I C Ibridge 5mA 0 06 Bridge Offset Tempco 1 TA 40 to 125 C noSet Reset 0 05 I C Vbridge 5V with Set Reset 0 001 Resistance Tempco 1 Vbridge 5V TA 40 to 125 C 0 25 I C Cross Axis Effect 1 Cross field 1 gauss see AN 205 Happlied2 1 gauss 0 3 FS Max Exposed Field 1 No perming effect on zero reading 10000 gauss Set Reset 1 S R current gt 0 5 Amps 30 uV Please reference data sheet HTMC1021D for specifications 1 Not tested in production g
22. then a series dropping resistor 500Q should be placed between the 4 7uF capacitor and the supply MAX662A 2 3 Ct C2 7 0 22uF 0 22yF LH 1 c2 38 SHDN 1pF a L 7 GND 6 al 5 Vout SL PET 5V 5 1N5818 1yF Vcc V 2uF aay WV 1pgF V Use tantalum capacitors Figure 7 5V to 20V Converter 16 to 20V 4 7yF 3 p 74HC04 PUR 2 KS Clock 9 I 8 c 3 4 3 2 S R strap 4 50 typ gt AA M gt Allon 3A peak min K EE lS HMC2003 1N4001 nF P 10K 4 0 1uF E NT T oc p Y ak q 2N3904 5 6 25K _ AA 5 6 2 7 8 V S R D inF 1 EL n NA NA 1 HEXFETs with 20 20 Ron 2 0 22uF Tantalum or a 0 68 uF Ceramic CK06 3 Tantalum low R Figure 8 Single Clock Set Reset Pulse Circuit 1001 1002 16 to 20V 5V7 SET Pr 1 25K 25K RESET Trs J TsR 2 gt 3 S R strap 4 59 typ lel la 3A peak min 4 x 16 7 1 S HMC2003 oy 10K 0 1pF T BE E O22yF 17 1 S R 5 6 ES 2N3904 TPW 2 7 8 o NV TRS 2 5 usec tev reset RESET 9 m S R TSR 2 5 usec 1 TPW 2 usec lt lt 7 1 Tantalum low R 7 2 HEXFETs with 0 20 Ron HMC2003 contains one HMC1001 and one HMC1002 together they make the 3 axis sensor Three S R straps are in serial the total resistance is 4 5Q Figure 9 Set Res
23. thin the automobile the effect of the car on the earth s magnetic field can be approximated as a shift or offset in this field If this shift in the earth s field can be determined then it can be compensated for by applying an equal and opposite field using the OFFSET strap Another use for the OFFSET strap would be to drive a current through the strap that will exactly cancel out the field being measured This is called aclosed loop configuration where the currentfeedback signal is a direct measure of the applied field The field offset strap OFFSET and OFFSET will generate a magnetic field in the same direction as the applied field being measured This strap provides a 1 Oersted Oe field per 50 mA of current through itin HMC1001 2 and 1 Oe bmA in HMC1021 2 Note 1 gauss 1 Oersted in air For example if 25 mA were driven from the OFFSET pin to the OFFSET pin in HMC1001 2 a field of 0 5 gauss would be added to any ambient field being measured Also a current of 25 mA would subtract 0 5 gauss from the ambient field The OFFSET strap looks like as a nominal resistance between the OFFSET and OFFSET pins The OFFSET strap can be used as a feedback element in a closed loop circuit Using the OFFSET strap in a current feedback loop can produce desirable results for measuring magnetic fields To do this connect the output of the bridge amplifier to a current source that drives the OFFSET strap Using high gain and negative feedba
24. uaranteed by characterization Units 1 gauss G 1 Oersted in air 1G 79 58 A m 1G 10E 4 Tesla 1G 10E5 gamma Tested at 25 C except otherwise stated LINEAR MAGNETIC FIELD SENSORS KEY PERFORMANCE DATA Sensor output vs magnetic field after being set or reset N 1021 1022 a 10 x ELE Vb 5V a E is S 5 N m E E b p gf 2 D gt 0 es 2 Nea 6 o A Reset gt N o 5 3 P bw Set Sg 8 N 6 10 y SS gt B 2 sweeps N 45 ue S u is 20 2 1 0 1 2 Field Oe Sensor noise vs frequency 1000 1021 1022 Vb 5V N z 8 100 SS gt gt E E 2 a 10 S 3 1 0 1 1 10 100 1000 Frequency Hz Bridge resistance vs temperature 1400 All types 1300 Vb 5V E gt 5 gt 1200 g 2 S 3 2 o 1100 5 aa z 1000 900 50 25 0 25 50 75 100 125 Temperature C Sensor output vs magnetic field Output is repeatable in field range 20 Oe 1021 1022 Vb 5V 20 45 10 5 0 5 10 15 20 Field Oe Sensitivity vs temperature n Constant voltage power supply 1021 1022 1 2 Vb 5V 1 4 4 1 L 0 9 0 8 0 7 0 6 50 25 0 25 50 75 100 125 Temperature C Effects of set reset pulse variation 2u sec pulse duration S R voltage gt 4V is recommended 1 Vb 5V 1021 1022 Null Voltage mV Set Null Voltage mV Reset amp Sensitivity mV V Oe Set Sensitivity mV V Oe Reset n
25. xis S R provides 1KHz rolloff Pulse sng enag Figure 18 One Axis Sensor With Constant Bridge Current and Digital Interface 5V 10K Sw1 VBRIDGE2 Sensitive 4 7uF tantalum S R 3 w GND4 a OUT 1 Y Direction S R 5 bud w OFFSET 6 mmm OFFSET 7 OUT 8 HMC1021Z 5V O v O Vout N LM404 2 5 O Gnd 1 Momentarily close switch SW1 This creates a SET pulse 2 Measure bridge output OUT OUT NOTE Bridge output signal will be 5mV gauss 3 Measure Vout after AD623 amplifier G 500 NOTE Vout signal will be 2 5V gauss Figure 19 0One Axis Low Cost Sensor eoepelu sng jenas Figure 17 One Axis Sensor With Digital Interface strong 200 gauss and have one of its magnetic poles point along the sensitive direction of the sensor This circuit can be used to detect a door open closed status or the presence or absence of an item Figures 17 18 19 20 and 21 show other circuit examples 12 LINEAR MAGNETIC FIELD SENSORS Magnetic Sensors TLC2543 12 bit A D 1 AINO V4 H9 5V AINT CLK o DIN Z 22 qz M Ret DOUTCS ae 131 Rel NcS 5 ae 10 Gnd Eoc 0 Vv 5V 25K LM440 2 5V 718 16 M
26. y herein to improve reliability function or design Honeywell does not assume any liability arising out of the application or use of any product or circuit described herein neither does it convey any license under its patent rights nor the rights of others Honeywell 900248 Rev B 4 00
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