ADT001/ADT002 Rotation Sensors
ADT00X-10E Ultralow Power Rotation Sensors
Features
•
Tunneling Magnetoresistance (TMR) technology
•
Extremely low power (1.8
μA
typ. at 2.4 V)
•
Precision digital quadrant outputs
•
Wide airgap tolerance
•
Operates with as little as 30 Oersteds of magnetic field
•
Integrated fault detection
•
2.4 V to 5.5 V supply range
•
−40°C
to +125°C operating range
•
Ultraminiature TDFN6 packages
Functional Diagram and Pinout
Applications
•
Water meters
•
Rotational speed sensors
•
Rotational position sensors
Vdd
Ro
ion
tat
GND
Angular
Sensor
Sin
Description
The ADT001 and ADT002 rotation sensors are ultralow
power, digital-output magnetic rotation sensors.
Tunneling Magnetoresistance (TMR) technology allows
small size and low power, making the sensors ideal for
battery operation.
The sensors have two digital, binary outputs. The two
outputs are 90 degrees out of phase to provide directional
information.
An additional output indicates a fault if the magnetic field
is too high for accurate measurements.
The ADT001 is optimized for edge-sensitive applications
and the ADT002 for absolute position. The ADT001 has
high hysteresis for noise immunity in applications such as
speed sensing and counting rotations. The ADT002 is low
hysteresis to provide accurate, absolute rotational quadrant
information.
Cos
FAULT
Fault
Sensor
Fault
Threshold
Adjust
Truth Table
Output
Sin
Cos
H
H
H
L
L
L
L
H
Angle
0 -90
90 -180
180 -270
270 -360
The parts are packaged in NVE’s 2.5 mm x 2.5 mm x
0.8 mm TDFN6 surface-mount package.
1
NVE Corporation
11409 Valley View Road, Eden Prairie, MN 55344-3617
Phone: (952) 829-9217
Fax: (952) 829-9189
www.nve.com
©NVE Corporation
ADT001/ADT002 Rotation Sensors
Absolute Maximum Ratings
Parameter
Supply Voltage
Storage Temperature
ESD (Human Body Model)
Applied Magnetic Field
Min.
−0.5
−40
Max.
7
170
2000
Unlimited
Units
Volts
°C
Volts
Oe
Operating Specifications
T
min
to T
max
; 2.4 V < V
DD
< 5.5 V unless otherwise stated.
Symbol
Min.
Typ.
Max.
T
min
; T
max
−40
125
V
DD
2.4
5.5
0.55
1.8
3.1
2.2
I
DDQ
0.8
2.7
4.6
6.95
30
200
200
V
OL
V
OH
|
θ
H
− θ
L
|
f
MAX
0
V
DD
−
0.25
12
3
2
20
4
300
500
0.24
V
DD
±1.5
28
6
Parameter
Operating Temperature
Supply Voltage
Supply Current
Applied Magnetic Field Strength
Units
°C
V
μA
Oe
Oe
V
V
deg.
deg.
kHz
Test Condition
V
DD
= 2.4V
V
DD
= 3V
3V < V
DD
< 3.6V
V
DD
= 5.5V
Pin 4 not
connected;
field in any
direction
I
L
=
−50 μA
I
L
= 50
μA
V
DD
= 3.6V; 25°C
Fault Output Field Strength Threshold
Low-Level Output Voltage
High-Level Output Voltage
Angular Precision/Repeatability
Angular Hysteresis
ADT001
ADT002
Frequency Response
2
NVE Corporation
11409 Valley View Road, Eden Prairie, MN 55344-3617
Phone: (952) 829-9217
Fax: (952) 829-9189
www.nve.com
©NVE Corporation
ADT001/ADT002 Rotation Sensors
Operation
Overview
The heart of the unique sensor is an array of four Tunneling Magnetoresistance (TMR) elements, one in each quadrant. TMR
technology enables low power and miniaturization, making the sensors ideal for battery operation.
In a typical configuration, an external magnet provides a saturating magnetic field (30 to 200 Oe) in the plane of the sensor, as
illustrated below for a bar magnet and a radially-magnetized disk magnet:
Figure 1. Sensor operation.
Simple output encoding
The rotation is encoded in two quadrature outputs, 90 degrees out of phase. Mathematically, the outputs correspond to the sign of
the sine and cosine of the rotation, i.e., sgn(sinθ) and sgn(cosθ), as shown below:
Outputs
Cos
Sin
0
90˚
180˚ 270˚
Rotation (CCW)
360˚
Figure 2. Sensor outputs
(counterclockwise rotation viewed from the top of the sensor).
Thus the binary sensor outputs define the quadrant of rotation:
Figure 3. Sensor outputs for each rotation quadrant.
3
NVE Corporation
11409 Valley View Road, Eden Prairie, MN 55344-3617
Phone: (952) 829-9217
Fax: (952) 829-9189
www.nve.com
©NVE Corporation
ADT001/ADT002 Rotation Sensors
Wide range of magnets and magnet location
The sensor operates with as little as a 30 Oe magnetic field, and is accurate up to 200 Oe. This wide magnetic field range allows
inexpensive magnets and operation over a wide range of magnet spacing. Larger or stronger magnets require more distance to
avoid oversaturating the sensor; smaller or weaker magnets may require closer spacing. Low-cost, radially-magnetized ferrite disk
magnets can be used with these sensors. Bar magnets can also be used in some configurations.
When locating the magnet in relation to the sensor, note that the rotational center of the sensor is offset slightly from the package
center (see Figure 11).
Absolute position
Unlike some encoder types, ADT001/ADT002 sensors detect absolute position and maintain position information when the power
is removed. The sensor immediately powers up indicating the correct position.
Power supply decoupling and noise filtering
Since ADT00X sensor s are duty-cycled to reduce power consumption, a bypass capacitor should be used on V
DD
if the sensor is
powered by a power supply or a battery with long connections. 10 nF ceramic capacitors are typical.
Because the sensor uses high-impedance circuitry and often operates in noisy environments, designers should consider filtering or
debounce circuitry on the sensor outputs if possible, especially if the application relies on triggering or counting edges.
Integrated fault detection
An additional output indicates a fault if the magnetic field is too high for accurate measurements. This can occur if the magnet is
too close to the sensor, or due to interference from adjacent magnets. The signal can also be used to align assemblies.
The signal is intended for gross sensing since the exact threshold depends on the particular device, field orientation, and supply
voltage, and can vary over temperature.
The fault detection threshold can be adjusted with an external resistor from pin 4 to ground, which increases the fault detection
threshold field as shown in Figure 4:
Vdd
1
GND
6
Sin
2
Cos
5
Fault
Threshold
Adjust
FAULT
3
4
ADT00X-10E
R
Figure 4. Fault threshold adjustment test circuit.
The typical effect of the external resistor value is shown in Figure 7.
4
NVE Corporation
11409 Valley View Road, Eden Prairie, MN 55344-3617
Phone: (952) 829-9217
Fax: (952) 829-9189
www.nve.com
©NVE Corporation
ADT001/ADT002 Rotation Sensors
Typical Performance Graphs
5
Quiescent Supply Current ( A)
4
3
2
1
0
2
2.5
3
3.5
4
Supply Voltage
4.5
5
5.5
Figure 5. Typical Quiescent Supply Current (25°C).
30
Angular Hysteresis (degrees)
25
20
15
10
5
ADT002
0
2
2.5
3
3.5
4
Supply Voltage
4.5
5
5.5
ADT001
Figure 6. Typical Angular Hysteresis vs. Supply Voltage (25°C).
600
Typical Fault Threshold (Oe)
500
400
300
200
100
0
0.5
R (M )
1
2
4
Figure 7. Typical fault threshold vs. external threshold adjust resistor (Fig. 4 test circuit).
5
NVE Corporation
11409 Valley View Road, Eden Prairie, MN 55344-3617
Phone: (952) 829-9217
Fax: (952) 829-9189
www.nve.com
©NVE Corporation
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