SENSOR PRODUCTS APPLICATIONS Compassing Navigation Systems 1- and 2-Axis Magnetic Sensors HMC1001 / 1002 HMC1021 / 1022 Attitude Reference Traffic Detection Medical Devices C onfigured as a 4-element wheatstone bridge, these magnetoresistive sensors convert magnetic fields to a differential output voltage, capable of sensing magnetic fields as low as 30 µgauss. These MRs offer a small, low cost, high sensitivity and high reliability solution for low field magnetic sensing.
LINEAR MAGNETIC FIELD SENSORS HMC1001/1002 SPECIFICATIONS Characteristics Conditions* Min Bridge Supply Vbridge referenced to GND Bridge Resistance Bridge current = 10mA Typ Max Unit 5 12 Volts 850 1200 ohm -55 150 °C 600 Operating Temperature (4) 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 0.1 1 0.5 2 %FS Hysteresis Error (4) 3 sweeps across ±2 gauss 0.05 0.
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 Ω Operating Temperature (1) HMC1021S, 1021Z, 1022 HMC1021D* -55 - 55 150 300* °C Storage Temperature (1) Unbiased -55 175 °C Field Range (1) Full scale (FS), — total applied field -6 +6 gauss Linearity Error (1) Best fit straight line ±1 gauss ±3 gauss ±6 gauss 0.05 0.
LINEAR MAGNETIC FIELD SENSORS KEY PERFORMANCE DATA Sensor output vs magnetic field Output is repeatable in field range ±20 Oe Sensor output vs magnetic field after being set or reset 15 60 1021/1022 1021/1022 10 40 Voltage Output (mV) Output Voltage (mV) Vb=5V 5 0 Reset -5 Set -10 Vb=5V 20 0 -20 2 sweeps 2 sweeps -40 -15 -60 -20 -2 -1 0 1 -20 2 -15 -10 -5 0 5 Sensor noise vs frequency 15 20 Sensitivity vs temperature Constant voltage power supply 1.
LINEAR MAGNETIC FIELD SENSORS PACKAGE / PINOUT SPECIFICATIONS HMC1001—One Axis MR Microcircuit HMC1002—Two-Axis MR Microcircuit GND1 (A) 1 20 S/R- (A) OUT+ (A) 2 Die A OFFSET- (A) 3 Vbridge (A) 4 18 GND PLN 17 OFFSET (+A) OUT- (A) 5 16 S/R+ (A) GND2 (A) 6 Die B S/R- (B) 7 15 OFFSET+ (B) 14 S/R+ (B) GND1 (B) 8 13 GND2 (B) Out+ (B) 9 12 OUT- (B) OFFSET- (B) 10 11 Vbridge (B) HMC1022—Two-Axis MR Circuit OFFSET- (A) OUT+ (A) VBRIDGE (A) OUT- (A) OUT- (B) VBRIDGE (B) GND (A) S/R+ (B) 1 2 3 4
LINEAR MAGNETIC FIELD SENSORS BASIC DEVICE OPERATION The OFFSET strap allows for several modes of operation when a dc current is driven through it. 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.
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/√Hz. This is approximately equivalent to the Johnson noise (or white noise) for an 850Ω resistor—the typical bridge resistance.
LINEAR MAGNETIC FIELD SENSORS WHAT IS SET/RESET STRAP? Most low field magnetic sensors will be affected by large magnetic disturbing fields (>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.
LINEAR MAGNETIC FIELD SENSORS 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 µF 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.
LINEAR MAGNETIC FIELD SENSORS Low Field Measurements—When measuring 100 µgauss 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.
LINEAR MAGNETIC FIELD SENSORS 200 1µF (1) +5 to 6V 5V 3 Clock HMC1022 4 4 to14V IRF7105 (2) DI9952 (2) set TPW ~ 2 µsec 14 8 9,15 0.1µF S/R reset set rst 5,6 7,8 2 Clock -4 to -14V S/R 1 set (1) Tantalum, low R (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-resistance (0.3Ω) at VGS=2.7V.
LINEAR MAGNETIC FIELD SENSORS Simple Circuit Application 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. 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 magnet is brought within 0.25 to 0.
LINEAR MAGNETIC FIELD SENSORS Magnetic Magnetic SensorS Sensors V+ 4 +5V 5 X 650 2 3 2 TLC2543 12 bit A/D 8 + 6 1 AMP04 2 V+ 11 +5V R3* Y 3 12 13 1.5nF# RefGnd 10 20 +5V 18 17 16 15 19 8 + R4* DOUT NCS EOC Ref+ 1 2 8,13 14 650 9 AIN1 5 Vref HMC1002 V+ CLK DIN AIN0 Serial Bus Interface R2* 1,6 1.5nF# 1 R1* 6 +5V AMP04 5 25K Vref 20 14 LM440 2.5V 1.6 1.6 7,18 16 MAX662A 3 * R1-R4 used to trim offest # provides 1KHz rolloff + 4 12V 4.
LINEAR MAGNETIC FIELD SENSORS PACKAGE OUTLINES HMC1002—Package Outline A1 D 20 11 E 1 H 10 h Millimeters Inches Symbol A A1 B D E e H h Max Min 2.642 2.489 0.279 0.127 0.483 0.457 12.675 12.929 7.417 7.264 1.270 ref 1.270 10.566 ref 0.381 Max Min .104 .098 .011 .005 .019 .014 .509 .499 .292 .286 .050 refref .416 .396 .030 .015 Symbol A A1 B D E e H h Min Max 1.371 1.728 0.101 0.249 0.355 0.483 9.829 11.253 3.810 3.988 1.270 ref 5.314 5.014 6.850 7.300 0.381 0.
LINEAR MAGNETIC FIELD SENSORS DESIGN / PACKAGE OPTIONS Two-axis parts contain two sensors for the x- and y- field measurements. Single-axis variations include a SIP package for mounting through the circuit board to create a 3-axis solution, a SOIC for direct surface mount, and a ceramic DIP for high performance military and high temperature applications. Honeywell offers a range of magnetic microcircuit products.