ZMT32 Magnetic Field Angle Sensor Description The ZMT32 is a thin film permalloy magnetic field sensor, which contains two galvanic isolated Wheatstone Bridges for high precision angle measurement applications under low field conditions. This angle sensor is based on the anisotropic magnetoresistive effect (AMR). The two internal (VCC1, VCC2) bridges enclose a relative sensitive angle of 45 degrees. The input field is a rotating magnetic field in the chip plane (parallel to the surface of package). This rotating field will make available two independent sinusoidal output signals with the following relationship The precise ZMT32 works with low field applications (Hrot= 8 to 25kA/m), much lower than similar devices. The ultimate output signal quality depends on the external magnetic material and on the mechanical realization. The ZMT32 is a passive part and the ArcTangent interpolation needs external signal processing. Typical areas of application are angle and speed measurement. VO 2 Sin(2α ) = = Tan(2α ) VO1 Cos (2α ) where α = angle between sensor axis and field direction Features Applications • contactless angle measurement up to 180° • angle and angular velocity measuring systems • flexible measuring solutions for moved systems • absolute angle and angle change • • stable operation over long time automotive electronic (steering, control, pedal positioning, etc • high temperature range up to +160°C • contactless rotary switches and potentiometer • automatic adjustment -VO1(cos) 1 8 GND (bridge 1) -VO2 (sin) 2 7 GND2 (bridge 2) VCC2(bridge 2) 3 6 +VO2 (sin) VCC1 (bridge 1) 4 5 +VO1 (cos) throttle Ordering Information Device Reel size (Inches) Tape width (mm) Quantity per reel Device marking ZMT32TA 7 12 1,000 ZETEX ZMT32 Issue 1 - June 2008 © Zetex Semiconductors plc 2008 1 www.zetex.com ZMT32 Absolute maximum ratings Parameter Symbol Limit Unit Supply Voltages Vcc1 and Vcc2 10 V Single Bridge Current Icc1 or Icc2 4 mA Operating Temperature Range TA -40 to +160 °C Storage Temperature Range Tstg -55 to +175 °C Recommended operating conditions Symbol Parameter Vcc1, Vcc2 Supply Voltages Hrot Applied Magnetic Field Strength Issue 1 - June 2008 © Zetex Semiconductors plc 2008 Min 8 2 Typ Max Unit 5 8.5 V 25 kA/m www.zetex.com ZMT32 Electrical characteristics General test conditions (unless otherwise noted) TA= +23±5oC, VCC1=VCC2 = +5V, HROT=25kA/m(†), k=100•(VPO1/VPO2) with VCC1=VCC2 SYMBOL Sα1 or Sα2 PARAMETER Sensitivities (zero crossing) Peak Output Voltages VPO1 or VPO2 (sinusoidal signals) k Amplitude bridge matching Temperature coefficient of TCk amplitude bridge matching RB1 or RB2 MAX UNIT mV/V/deg 40 50 60 mV 99.77 100 100.23 % -0.008 +0.008 %/K TA = -40°C 2017 3040 TA = 23°C 2500 TA = -40 to +160°C no HROT TA = +160°C TC of Bridge Resistances or Peak to peak output swing ∆VO2/VCC2A HROT = 8 kA/m(†) VOFF1/VCC1A or Output offset voltage HROT = 8 kA/m (†) A no HROT Angular Inaccuracy ∆αHA Angular hysteresis Iiso1-2 Isolation Bridge Current +0.32 +0.36 19.2 16 TA = +160°C 6.7 TA = 23°C 16 20 24 -0.35 -0.32 -0.28 24 13.4 -1.25 +1.25 TA = +160°C -1.55 +1.55 TA = 23°C HROT = 8 kA/m(†) no HROT 0 %/K 30.4 20 TA = -40°C -1 -2 -4 Ω 5114 TA = 23°C TC of output offset voltage ∆αA 3600 TA = -40°C TC of peak to peak output swing TCVOB 3000 3345 +0.28 ∆VO1/VCC1A TCVOFFB TYP (*) 0.35 α1=135°, α2=0° Bridge resistances TCRBB VOFF2/VCC2 MIN CONDITIONS mV/V %/K mV/V 0 0 0 +1 +2 +4 µV/V/K 0.05 0.2 deg 0.1 deg 0.5 (‡) deg 0.1 µA NOTES: (*) Typical values apply to an ambient temperature of 23oC (†) See point “Magnetic Field Tests” below (‡) The accurate control of this parameter (Limmax=0.1deg, HROT=25kA/m) takes place by means of sample tests A: Output characteristic definitions ∆VO1/VCC1 = (VOMAX1 – VOMIN1)/VCC1 or/ ∆VO2/VCC2 = (VOMAX2 – VOMIN2)/VCC2 VOFF1/VCC1 = ½(VOMAX1 + VOMIN1)/VCC1 or/ VOFF2/VCC2 = ½(VOMAX2 + VOMIN2)/VCC2 ∆αH = MAX | αLEFT TURN – αRIGHT TURN | ∆α = MAX | αo – α | (max. angular difference between left and right turn) (max. angular difference between actual value αoand measured angle, without offset error) B: Temperature coefficient (TC) equations T1 = -25°C, T0 = +25°C, ΔVO ΔVO (T2 ) − (T1) VCC VCC 1 × TCVO = × 100% ΔVO T2 − T1 (T0 ) VCC Issue 1 - June 2008 © Zetex Semiconductors plc 2008 T2 = +125°C where ΔVO (Tn ) VCC 3 is the peak-peak output voltage at temperature Tn www.zetex.com ZMT32 TCR B = R (T ) − R B (T1) 1 × B 2 × 100% T2 − T1 R B (T0 ) TCVOFF = where RB(Tn) is the bridge resistance at temperature Tn VOFF( T 2) − VOFF( T1) (T2 − T1 ) where VOFF(Tn) is the output offset voltage at temperature Tn Magnetic field tests For these tests a rotating magnetic field is generated and the output signals of both bridges are measured at four different field angles for right rotation as well as for left rotation. Using these measured output signals the diameter and the center coordinates of the best circle are calculated. They correspond to the output voltage range and the offset voltage. Furthermore the field angles for both rotation directions and angular hysteresis are calculated ⎛V ⎞ [measured angle] = α = arctan⎜⎜ O2 ⎟⎟ ⎝ VO1 ⎠ Method The data pairs are transformed onto a unit circle starting from their position in the data collection for determining direction information or angle information. It must be evaluated with four pair values (cos, sin) on a right rotation (magnetic field rotation) and four pair values (cos, sin) on a left rotation (magnetic field rotation). The field rotation steps are: Æ start in 180° position § right rotation to 22.5° with measurement of sensor outputs § right rotation to 67.5° with measurement of sensor outputs § right rotation to 112.5° with measurement of sensor outputs § right rotation to 157.5° with measurement of sensor outputs § right rotation to 0° (360°) , stop , reversal § left rotation to 157.5° with measurement of sensor outputs § left rotation to 112.5° with measurement of sensor outputs § left rotation to 67.5° with measurement of sensor outputs § left rotation to 22.5° with measurement of sensor outputs , end position General description of tests with external magnetic field. Issue 1 - June 2008 © Zetex Semiconductors plc 2008 4 www.zetex.com ZMT32 Operating principle 0 GND1 8 Hrot O +VO2 6 +VO1 5 Bridge 2 Bridge 1 α = 0° 1 GND2 7 ␣ 2 -VO2 1 -VO1 3 VCC2 4 VCC1 When a common-magnetic field is applied through the ZMT32 the 2 internal magneto-resistive bridges are affected slightly differently due to their 45° rotation to one another. This 45° rotation enables the ZMT32 to determine angular position, of a rotating magnetic field. GND1 When a rotating magnetic field is applied to the ZMT32 it will output 2 sinusoidal voltages that are: -VO2 GND2 • proportional to the field strength applied Vcc2 +VO2 • proportional to the supply voltage applied, Vcc1 +VO1 • rotating at twice the angular position • 90° apart (as seen below). 1 -VO1 By taking the arcTan of the ratio of VO2 to VO1 the angular position of the magnetic field can be determined. Characteristic output curves VO1, VO2 10 Cos 2α Output voltage (mV/V) 5 Sin 2α 0 -5 -10 Sensor bridge 2 Sensor bridge 1 -15 0 45 Issue 1 - June 2008 © Zetex Semiconductors plc 2008 90 135 180 225 5 270 315 360 www.zetex.com ZMT32 Typical characteristics Accuracy variance with field strength Angle accuracy 1.4% VCC1=VCC2=+5V 1.2% TA=23oC 1.0% k=100 0.8% 0.6% 0.4% 0.2% 0.0% 0 10 20 30 40 50 HROT - Field strength (kA/m) Output voltage (mV/V) Output variance with magnetic field strength 25 20 VCC1=VCC2=+5V TA=23oC 15 k=100 10 5 0 0 10 20 30 40 50 HROT - Field strength (kA/m) Issue 1 - June 2008 © Zetex Semiconductors plc 2008 6 www.zetex.com ZMT32 Typical characteristics Output voltage versus temperature Output voltage (mV/V) 35 MAX 30 MIN 25 20 15 VCC1=VCC2=+5V 10 TA=23oC k=100 5 0 -50 -25 0 25 50 75 100 125 150 175 Temperature (oC) Bridge resistance (Ω) Bridge resistance versus temperature 6000 VCC1=VCC2=+5V 5000 TA=23oC 4000 k=100 3000 2000 MAX 1000 MIN 0 -50 -25 0 25 50 75 100 125 150 175 Temperature (oC) Issue 1 - June 2008 © Zetex Semiconductors plc 2008 7 www.zetex.com Issue 1 - June 2008 © Zetex Semiconductors plc 2008 8 1 R4 R3 8 SIN R2 R1 R3 R4 COS R1 4 top view ZMT32T8 5 R2 + - + VOUT2 A A fixed 45 degree phase difference between outputs 1 and 2 VOUT1 D D p tan GND result of angle measurement +VCC ZMT32 Typical application www.zetex.com ZMT32 Package outline - SM-8 Soldering footprint 2.8 0.110 4.6 0.181 6.8 0.268 mm inches 0.95 0.037 DIM Millimeters Inches DIM 1.52 0.060 Millimeters Inches Min. Max. Typ. Min. Max. Typ. Min. Max. Typ. Min. Max. Typ. A - 1.7 - - 0.067 - e1 - - 4.59 - - 0.1807 A1 0.02 0.1 - 0.0008 0.004 - e2 - - 1.53 - - 0.0602 b - - 0.7 - - 0.0275 He 6.7 7.3 - 0.264 0.287 - c 0.24 0.32 - 0.009 0.013 - Lp 0.9 - - 0.035 - - D 6.3 6.7 - 0.248 0.264 - ␣ - 15° - - 15° - E 3.3 3.7 - 0.130 0.145 -  - - 10° - - 10° Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches Issue 1 - June 2008 © Zetex Semiconductors plc 2008 9 www.zetex.com ZMT32 Definitions Product change Zetex Semiconductors reserves the right to alter, without notice, specifications, design, price or conditions of supply of any product or service. Customers are solely responsible for obtaining the latest relevant information before placing orders. Applications disclaimer The circuits in this design/application note are offered as design ideas. 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Life support devices or systems are devices or systems which: 1. are intended to implant into the body or 2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labelling can be reasonably expected to result in significant injury to the user. B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or to affect its safety or effectiveness. Reproduction The product specifications contained in this publication are issued to provide outline information only which (unless agreed by the company in writing) may not be used, applied or reproduced for any purpose or form part of any order or contract or be regarded as a representation relating to the products or services concerned. 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Samples may be available “Active” Product status recommended for new designs “Last time buy (LTB)” Device will be discontinued and last time buy period and delivery is in effect “Not recommended for new designs” Device is still in production to support existing designs and production “Obsolete” Production has been discontinued Datasheet status key: “Draft version” This term denotes a very early datasheet version and contains highly provisional information, which may change in any manner without notice. “Provisional version” This term denotes a pre-release datasheet. It provides a clear indication of anticipated performance. However, changes to the test conditions and specifications may occur, at any time and without notice. “Issue” This term denotes an issued datasheet containing finalized specifications. However, changes to specifications may occur, at any time and without notice. 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