Analog Devices AD22151X Datasheet
REV. 0
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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
DEMODSWITCHES
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 requirements 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 operation over –40°C to +150°C. Temperature compensation can
accommodate a number of magnetic materials commonly utilized in economic position sensor assemblies.
The transducer may be configured for specific signal gains dependent 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 signal is ratiometric to the positive supply rail in all configurations.
NC
R1
GND
R3
R2
V
CC
AD22151
NC = NO CONNECT
OUTPUT
0.1mF
Figure 1. Typical Bipolar Configuration with Low
(< –500 ppm) Compensation
NC
R1
GND
R3
R2
V
CC
AD22151
NC = NO CONNECT
OUTPUT
0.1mF
R4
Figure 2. Typical Unipolar Configuration with High
(≈
–2000 ppm) Compensation
–2–
REV. 0
AD22151–SPECIFICA TIONS
(TA = +258C and V+ = +5 V unless otherwise noted)
Parameters Min Typ Max Units
OPERATION
VCC Operating 4.5 5.0 6.0 V
ICC Operating 6.0 10 mA
INPUT
TC3 (Pin 3) Sensitivity/Volt 160 µV/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
RL = 4.7 kΩ.
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
–3–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 3 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 provide a resultant offset cancellation (see Figure 3). The demodulated 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 – 8C
0.005
–0.004
140 –40120
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 associated 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 mechanism 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 temperature 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 factoring into the total temperature compensation of the sensor
assembly.
Figures 5 and 6 represent typical overall temperature/gain performance 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 temperature 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 – 8C
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
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