provides the HMC1021D advantages over other magnetic sensors with a
wheatstone bridge to convert magnetic fields to differential output voltage.
Capable of sensing magnetic field strength and direction down to 85 micro-
gauss, this sensor offers a compact and highly reliable solution for low field
magnetic sensing.
Honeywell continues to maintain product excellence and performance by
introducing innovative solid-state magnetic sensor solutions. These are highly reliable, top performance products that are
delivered when promised. Honeywell’s magnetic sensor solutions provide real solutions you can count on.
FEATURES
High Temperature Operating Range
One-Axis DIP Package
On-Chip Set/Reset Straps
On-Chip Offset Straps
High Sensitivity
High Reliability
Available in High Volumes
BENEFITS
From -55°C to +225°C, Perfect for Downhole Applications
Easy to Assemble Component.
Reduces Temperature Effects, High Field Upset Resistance
Counters Hard-Iron Distortion
Low-Noise Signals for Amplification and Detection
Compact Solid State Design with Repeatable Results.
Easy Transition to Production
HMC1021D
SPECIFICATIONS
Characteristics
Bridge Elements
Supply
Resistance
Operating Temperature
Storage Temperature
Humidity
Field Range
Linearity Error
Full scale (FS) – total applied field
Best fit straight line
± 1 gauss
± 3 gauss
± 6 gauss
3 sweeps across ±3 gauss
3 sweeps across ±3 gauss
Offset = (OUT+) – (OUT-)
Field = 0 gauss after Set pulse, Vbridge = 5V
Set/Reset Current = 2.0A
@ 1kHz, Vbridge=5V
50Hz Bandwidth, Vbridge=5V
Magnetic signal (lower limit = DC)
Sensitivity starts to degrade.
Use S/R pulse to restore sensitivity.
T
A
= -40 to 225°C, Vbridge=5V
T
A
= -40 to 225°C, Ibridge=5mA
T
A
= -40 to 225°C, No Set/Reset
T
A
= -40 to 225°C, With Set/Reset
Vbridge=5V, T
A
= -40 to 225°C
Cross field = 1 gauss, Happlied = ±1 gauss
No perming effect on zero reading
2100
20
2
-2800
-3000
-600
±500
±10
2500
+0.3
200
20
5.5
0.5
3300
40
4.0
3500
7.7
0.5
3700
50
4.6
3900
9.0
4.0
4100
60
6.0
4300
2900
-3200
-6
-0.6
0.05
0.4
1.6
0.08
0.08
±2.5
1.0
0.01
48
85
8.5
5
Vbridge referenced to GND
Bridge current = 5mA, Vbridge to GND
Ambient
Ambient, unbiased
-55
-55
1.8
5.0
1100
225
175
100
+6
+0.6
12
Volts
ohms
°C
°C
%
Gauss
milli-Tesla
%FS
%FS
%FS
mV
mV/V/gauss
V/V/nT
nV/sqrt Hz
gauss
nT
MHz
Gauss
milli-Tesla
ppm/°C
ppm/°C
ppm/°C
%FS
Gauss
milli-Tesla
ohms
Amp
ppm/°C
ohms
mA/gauss
ppm/°C
Conditions*
Min
Typ
Max
Units
Hysteresis Error
Repeatability Error
Bridge Offset
Sensitivity
Noise Density
Resolution
Bandwidth
Disturbing Field
Sensitivity Tempco
Bridge Offset Tempco
Bridge Ohmic Tempco
Cross-Axis Effect
Max. Exposed Field
Set/Reset Strap
Resistance
Current
Resistance Tempco
Offset Straps
Resistance
Offset Constant
Measured from S/R+ to S/R-
0.1% duty cycle, or less, 2 sec current pulse
T
A
= -55°C to +225°C
Measured from OFFSET+ to OFFSET-
DC Current
Field applied in sensitive direction
Resistance Tempco
T
A
= -55°C to +225°C
* Tested at 25°C except stated otherwise.
2
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HMC1021D
PIN CONFIGURATION
(Arrow indicates direction of applied field that generates a positive output voltage after a SET pulse.)
OUT+ 1
VBRIDGE 2
DIE
GND
OUT-
3
4
8 OFFSET-
7 OFFSET+
6 S/R-
5 S/R+
BASIC DEVICE OPERATION
The Honeywell HMC1021D magneto-resistive sensor is composed of a Wheatstone bridge element to measure magnetic
fields for both field strength and direction. With power applied to the bridge, the sensor element converts any incident
magnetic field in the element’s sensitive axis direction to a differential voltage output. In addition to the bridge element, the
sensor has two types of on-chip magnetically coupled straps; the offset strap and the set/reset strap. These straps are
Honeywell patented features for incident field adjustment and magnetic domain alignment; and eliminate the need for
external coils positioned around the sensors.
The magnetoresistive sensor is made of a nickel-iron (Permalloy) thin-film deposited on a silicon wafer and patterned as a
resistive strip element die. Using semiconductor processes, the wafer is diced and packaged in a custom ceramic DIP IC
package with a low magnetic lead frame. In the presence of a magnetic field, a change in the bridge resistive element
causes a corresponding change in voltage across the bridge output (OUT – and OUT+ pins).
This resistive element is aligned to have a sensitive axis (indicated by the arrow on the pinout) that will provide positive
voltage change with magnetic fields increasing in the sensitive direction. Because the output only is in proportion to the
one-dimensional axis (the principle of anisotropy) and its magnitude, additional sensor bridges placed at orthogonal
directions permit accurate measurement of arbitrary field direction. The combination of sensor bridges in two or three
orthogonal axis configurations permit applications such as compassing and magnetometry.
The sensor offset strap allows for several modes of operation when a direct current is driven through it. These modes are:
1) Subtraction (bucking) of an unwanted external magnetic field, 2) null-ing of the bridge offset voltage, 3) Closed loop
field cancellation, and 4) Auto-calibration of bridge gain.
The set/reset strap can be pulsed with high currents for the following benefits: 1) Enable the sensor to perform high
sensitivity measurements, 2) Flip the polarity of the bridge output voltage, and 3) Periodically used to improve linearity,
lower cross-axis effects, and temperature effects.
Noise Characteristics
The noise density for the HMR1021D is around 50nV/sqrt Hz at the 1 Hz corner, and drops below 10nV/sqrt Hz at 20Hz
and begins to fit the Johnson Noise value at around 5nV/sqrt Hz beyond 100Hz. The 10Hz noise voltage averages around
0.58 micro-volts with a 0.16 micro-volts standard deviation. These values are provided with a 5-volt supply.
Offset Strap
The offset strap is a spiral of metallization that couples in the sensor element’s sensitive axis. The offset strap measures
nominally 50 ohms, and requires about 4.6mA for each gauss of induced field. The strap will easily handle currents to
buck or boost fields through the ±6 gauss linear measurement range, but designers should note the extreme thermal
heating on the sensor die when doing so.
With most applications, the offset strap is not utilized and can be ignored. Designers can leave one or both strap
connections (Off- and Off+) open circuited, or ground one connection node. Do not tie positive and negative strap
connections together of the same strap to avoid shorted turn magnetic circuits.
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3
HMC1021D
Set/Reset Strap
The set/reset strap is another spiral of metallization that couples to the sensor element’s easy axis (perpendicular to the
sensitive axis on the sensor die). The set/reset strap connections have a nominal resistance of 7.7 ohms with a minimum
required peak current of 0.5A for reset or set pulses. With rare exception, the set/reset strap must be used to periodically
condition the magnetic domains of the magneto-resistive elements for best and reliable performance.
A set pulse is defined as a positive pulse current entering the S/R+ strap connection. The successful result would be the
magnetic domains aligned in a forward easy-axis direction so that the sensor bridge’s polarity is a positive slope with
positive fields on the sensitive axis result in positive voltages across the bridge output connections. A reset pulse is
defined as a negative pulse current entering the S/R+ strap connection. The successful result would be the magnetic
domains aligned in a reverse easy-axis direction so that sensor bridge’s polarity is a negative slope with positive fields on
the sensitive axis result in negative voltages across the bridge output connections.
ORDERING INFORMATION
Ordering Number
HMC1021D
Product
One-Axis High Temperature Magnetic Sensor
FIND OUT MORE
For more information on Honeywell’s Magnetic Sensors visit us online at www.magneticsensors.com or contact us at
800-323-8295 (763-954-2474 internationally).
The application circuits herein constitute typical usage and interface of Honeywell product. Honeywell does not warranty or assume liability of customer-
designed circuits derived from this description or depiction.
Honeywell reserves the right to make changes 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.
U.S. Patents 4,441,072, 4,533,872, 4,569,742, 4,681,812, 4,847,584 and 6,529,114 apply to the technology described
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