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Analog Devices Semiconductor Electronic Components Datasheet

AD22157 Datasheet

Wheel Speed Sensor

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PRELIMINARY TECHNICAL DATA
Wheel Speed Sensor For
ABS Systems
Preliminary Technical Data
FEATURES
Speed and direction from 0Hz to 2500Hz
Air gap diagnostics
2-wire current-loop operation
Wide Operating Temperature Range
Functional during temperature excursions to 190C
Reverse Supply Protected (-30V)
APPLICATIONS
Automotive
Wheel speed and direction sensing
Transmission speed sensing
Industrial
Incremental position sensing
Proximity switching
AD22157
Functional Block Diagram
Vhigh
Tracker 1
PWM
7mA 7mA
Tracker 2
AD22157
Vlow
GENERAL DESCRIPTION
The AD22157 is a mixed signal magnetic field transducer
designed for applications where both speed sensing and direc-
tion sensing of a ferrous target wheel are required over a wide
speed range.
The device operates from a 2 wire high compliance current loop
and is suitable for continuous operation from -40C to 150C with
supplies up to +20 Vdc. The sensor is designed to remain func-
tional during voltage transients up to +27V.
The sensor output format is a current pulse from 7mA to 14mA
(the quiescent bias is 7mA) whose rising edge is accurately
placed relative to the edges of the target wheel. The pulse width
is determined by both target wheel direction and field strength.
The output pulse is coded in multiples of a well defined time
interval depending on direction and field strength in conform-
ance with industry standards currently being promoted by lead-
ing systems manufacturers.
Pulse widths corresponding to differential magnetic fields mea-
sured at the sensor of B >4mT (normal operation),
2mT<B<4mT (low field range), and B<2mT (very low field
range) are provided. Direction is indicated in the normal and
low ranges.
A fail safe stop signal repeating at approximately 1.5Hz is pro-
vided initially at power on, if the target wheel is stopped, or if
no dynamic signal is detected for some other reason.
The sensor combines integrated bulk Hall cell technology and
instrumentation circuitry to minimize temperature related drifts
REV. PrA
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 which may result from its use.
No license is granted by implication or otherwise under any patent or patent rights of
Analog Devices.
associated with Hall cell characteristics. The sensor is compen-
sated to work optimally with SmCo magnets. The architecture
maximizes the advantages of fine line CMOS and high voltage
DMOS allowing the device to operate accurately in demanding
environments.
Principle features of the AD22157 include an adaptive differen-
tial zero crossing detector which accurately determines the posi-
tion of target wheel edges. This architecture eliminates the
effects of package and thermal stress on the Hall sensor array
resulting in 2% repeatability of the time interval from rising
edge to rising edge of the sensor output.
The sensor takes 4 edges from either power on or a stopped con-
dition to achieve full accuracy. The architecture employs digital
signal processing to provide robust functionality and eliminate
spurious or missing pulses under extreme conditions of EMC.
The AD22157 is housed in a 5 lead single-in-line (SIP) package
suitable for mounting with a back biasing magnet in a typical
wheel speed sensor assembly.
One Technology Way, P.O. Box 9106, Norwood, MA02062-9106,USA
www.analog.com
Analog Devices, Inc.,2001
-1-


Analog Devices Semiconductor Electronic Components Datasheet

AD22157 Datasheet

Wheel Speed Sensor

No Preview Available !

PRELIMINARY TECHNICAL DATA
Preliminary AD22157 - Specifications (TA=+25C and V+=12V unless otherwise noted)
Parameters
OPERATING TEMPERATURE
POWER SUPPLY
Vcc Operating
Vcc max transient
Reverse Supply
SUPPLY CURRENT
Iout low
Iout high (pulsed)
OUTPUT CURENT RATIO
OUTPUT CURRENT PULSE WIDTH1
Nominal field operation (left/right)
Low field operation (left/right)
Air gap limit
No field or stopped for >737mS
PULSE PERIOD IN STOPPED MODE
THRESHOLDS FOR OPERATION MODES
Nominal field threshold
Low field threshold
Field too low threshold
POWER ON TIME
CALIBRATION CYCLE
CALIBRATION UPDATE CYCLE
TIMING ACCURACY2
Min
-40
4.5
5.5
11.0
1.8
72/144
288/576
36
1152
589
Typ
7.0
14.0
2
90/180
360/720
45
1440
737
4<Bth
2<Bth<4
Bth<2
4
4
each edge
2
Max
150
20.0
27.0
-30.0
8.5
17.0
2.2
108/216
432/664
54
1728
884
Units
C
V
mA
uS
mS
mT
mS
edges
%
NOTES
1 Left: wheel moving from pin 1 to pin 5 with the front of the AD22157 facing the wheel (see figure 7).
2 Timing wheel with 2.5mm tooth/2.5mm valley and 5mmx4mm SmCo magnet.
ABSOLUTE MAXIMUM RATINGS*
Maximum Supply Voltage . . . . . . . . . . . . . . . . . . . . . +27 V
Maximum Output Current (Pin 2) . . . . . . . . . . . . . . 18 mA
Operating Temperature Range . . . . . . . . . –40°C to +150°C
Die Junction Temperature . . . . . . . . . . . . . . . . . . . .+190°C
Storage Temperature Range . . . . . . . . . . –65°C to +160°C
Lead Temperature (Soldering, 10 sec) . . . . . . . . . . +300°C
*Stresses above those listed under “Absolute Maximum Ratings” may cause permanent
damage to the device. This is a stress rating only and functional operation of the device
at these or any other conditions above those listed in the operational sections of this spec-
ification is not implied. Exposure to absolute maximum rating conditions for extended
periods may affect device reliability.
Pin Configuration
5
4
3
2
1
PIN 1 IDENTIFIER
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
AD22157 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.
-2-
NC
NC
Vlow
Vhigh
NC
REV. PrA


Part Number AD22157
Description Wheel Speed Sensor
Maker Analog Devices
Total Page 7 Pages
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