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PDF AD22151 Data sheet ( Hoja de datos )
| Número de pieza | AD22151 | |
| Descripción | Linear Output Magnetic Field Sensor | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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Linear Output
Magnetic Field Sensor
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 VCC
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 require-
ments with a minimum number of components.
Principal features include dynamic offset drift cancellation
and a built-in temperature sensor. Designed for single 5 V
supply operation, the AD22151 achieves low drift offset and
gain operation over –40∞C to +150∞C. Temperature compensa-
tion can accommodate a number of magnetic materials commonly
utilized in economic position sensor assemblies.
The transducer can be configured for specific signal gains to
meet various 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.
FUNCTIONAL BLOCK DIAGRAM
VCC/2
TEMP REF
AD22151
ISOURCE
REF
OUT AMP
SWITCHES
DEMOD
NC
R1
VCC
R2
0.1F
R3
OUTPUT
GND
NC = NO CONNECT
AD22151
Figure 1. Typical Bipolar Configuration with Low
(< –500 ppm) Compensation
VCC
R1
R4
NC
R2
0.1F
R3
OUTPUT
REV. A
GND
NC = NO CONNECT
AD22151
Figure 2. Typical Unipolar Configuration with
High (Ϸ –2000 ppm) Compensation
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703 © 2003 Analog Devices, Inc. All rights reserved.
1 page  
to self-heating as a function of power dissipation. Second, pack-
age stress effect alters the specific operating parameters of the
gain compensation, particularly the specific crossover tempera-
ture of TC1, TC3 ( Ϸ ± 10∞C).
CONFIGURATION AND COMPONENT SELECTION
There are three areas of sensor operation that require external
component selection: temperature compensation (R1), signal
gain (R2 and R3), and offset (R4).
Temperature
If the internal gain compensation is used, an external resistor is
required to complete the gain TC circuit at Pin 3. A number of
factors contribute to the value of this resistor:
a. The intrinsic Hall cell sensitivity TC Ϸ 950 ppm.
b. Package induced stress variation in a. Ϸ ± 150 ppm.
c. Specific field TC Ϸ –200 ppm (Alnico), –2000 ppm
(Ferrite), 0 ppm (electromagnet), and so on.
d. R1, TC.
The final value of target compensation also dictates the use of
either Pin 1 or Pin 2. Pin 1 is provided to allow for large nega-
tive field TC devices such as ferrite magnets; thus, R1 would be
connected to Pins 1 and 3.
Pin 2 uses an internal resistive TC to optimize smaller field
coefficients such as Alnico down to 0 ppm coefficients when
only the sensor gain TC itself is dominant. Because the TC of
R1 itself will also affect the compensation, a low TC resistor
(± 50 ppm) is recommended.
Figures 10 and 11 indicate R1 resistor values and their associ-
ated effectiveness for Pins 1 and 2, respectively. Note that the
indicated drift response in both cases incorporates the intrinsic
Hall sensitivity TC (BTCU).
For example, the AD22151 sensor is to be used in conjunction
with an Alnico material permanent magnet. The TC of such mag-
nets is Ϸ –200 ppm (see Figures 5 and 6). Figure 11 indicates
that a compensating drift of 200 ppm at Pin 3 requires a nomi-
nal value of R1 = 18 kW (assuming negligible drift of R1 itself).
3500
3000
2500
2000
1500
1000
500
0
0 5 10 15 20 25 30
R1 – k⍀
Figure 10. Drift Compensation (Pins 1 and 3) vs.
Typical Resistor Value R1
AD22151
800
600
400
200
0
–200
–400
–600
0
5 10 15 20 25 30 35 40 45 50
R1 – k⍀
Figure 11. Drift Compensation (Pins 2 and 3) vs.
Typical Resistor Value R1
GAIN AND OFFSET
The operation of the AD22151 can be bipolar (i.e., 0 Gauss =
VCC/2), or a ratiometric offset can be implemented to position
Zero Gauss point at some other potential (i.e., 0.25 V).
The gain of the sensor can be set by the appropriate R2 and R3
resistor values (see Figure 1) such that:
Gain
=
1+
R3
R2
¥
0.4
mV
/G
(1)
However, if an offset is required to position the quiescent out-
put at some other voltage, the gain relationship is modified to:
( )Gain = 1 + R3 ¥ 0.4 mV / G
R2 R4
The offset that R4 introduces is:
(2)
Offset
=1+
R3
(R2 + R4)
(¥ VCC
)– VOUT
(3)
For example, at VCC = 5 V at room temperature, the internal gain of
the sensor is approximately 0.4 mV/Gauss. If a sensitivity of
6 mV/Gauss is required with a quiescent output voltage of 1 V,
the calculations below apply (see Figure 2).
A value would be selected for R3 that complied with the various
considerations of current and power dissipation, trim ranges (if
applicable), and so on. For the purpose of example, assume a
value of 85 kW.
To achieve a quiescent offset of 1 V requires a value for R4 as:
ÊËÁ
VCC
2
ˆ¯˜
VCC
–
1
=
0.375
Thus:
(4)
R4 = ÊËÁ 805.3k7W5ˆ¯˜ – 85 kW = 141.666 kW
(5)
The gain required would be 6/0.4 (mV/Gauss) = 15.
REV. A
–5–
5 Page | ||
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| PDF Descargar | [ Datasheet AD22151.PDF ] | |
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