AD-Series GMR Switches
AD-Series GMR Switch™ Precision Digital Magnetic Sensors
Functional Diagram
Vcc
Voltage
Regulator
(optional)
Short-
Circuit
Protection
(optional)
Features
•
Digital outputs
•
Precision magnetic operate points from 10 – 80 Oe
•
4.5 V – 30 V supply voltage
•
20 mA output drive
•
Temperature and voltage stability
•
Models available with short-circuit protection
•
Frequency response to 100 kHz
•
Ultraminiature TDFN6 and MSOP8 packages
GMR
Sensor
Element
Comparator
Output
Driver
OUT
Applications
•
Motion, speed, and position control
•
Pneumatic cylinder position sensing
•
Speed sensing
GND
Idealized Transfer Function
Description
AD-Series GMR Switches are the industry standard for
sensitivity and precision.
GMR Switches integrate GMR sensor elements with digital
signal processing electronics. These sensors are more precise
than other magnetic sensors, and magnetic field operate
points are stable over voltage and temperature extremes.
AD-Series models available in a wide variety of magnetic
operate points and output configurations. Versions are
available with short-circuit protection circuitry and with
integrated voltage regulators.
1
NVE Corporation
11409 Valley View Road, Eden Prairie, MN 55344-3617
Phone: (952) 829-9217
sensor-info@nve.com
www.nve.com
©NVE Corporation
AD-Series GMR Switches
Absolute Maximum Ratings
Parameter
Supply voltage
Except AD8xx/AD9xx
AD8xx/AD9xx
Symbol
V
CC
Min.
−33
−0.5
−0.5
−40
−65
H
Max.
33
33
5
125
150
2000
Unlimited
Units
Volts
Volts
mA
°C
°C
Volts
Oe
Test Conditions
Output voltage
Output current (AD8xx/AD9xx only)
Operating temperature
Storage temperature
ESD
Applied magnetic field
Operating Specifications
Parameter
Supply voltage
Operating temperature
Magnetic operate point
ADH025
AD004; AD021; AD621
AD024
AD005; AD022
AD006
Operate/release differential
ADH025
AD004; AD021; AD621
AD024
AD005; AD022
AD006
Except AD8xx/AD9xx
Supply current
AD8xx/AD9xx
Except AD8xx/AD9xx
Output current
AD8xx/AD9xx
Sinking
output voltage
Sourcing
output voltage
Except AD8xx/AD9xx
AD8xx/AD9xx
Except AD8xx/AD9xx
AD8xx/AD9xx
Human Body Model
Tmin to Tmax; 4.5 V < V
CC
< 30 V unless otherwise stated.
Symbol
Min.
Typ.
Max.
V
CC
4.5
30
T
MIN
; T
MAX
−40
125
8
15
21
30
60
2
5
5
5
5
2.5
1.75
20
2
0.2
0.4
V
CC
–2.5
V
CC
–2
10
0.12
5.8
V
REG
3.5
3.5
3
100
V
CC
– 0.9
5.8
V
CC
– 0.9
I
REG
f
MAX
θ
JA
2
Units
Volts
°C
Test Conditions
H
OP
10
20
28
40
80
12
25
33
50
100
8
14
15
25
50
4.5
3.5
Oe
H
OP
−H
REL
Oe
I
CC
I
O-ON
V
OL
V
OH
I
O-OFF
V
Short
mA
mA
V
CC
= 12V;
Output Off
Output On
V
CC
= 12V;
I
O
= 20mA
I
O
= 2mA
V
CC
= 12V;
I
O
= 20mA
I
O
= 2mA
V
CC
= 12V;
Output Off
Output On
V
CC
> 6.6V;
0 < I
REG
< 20mA
V
CC
< 6.6V
V
CC
> 6.6V;
0 < I
REG
< 20mA
V
CC
< 6.6V
Soldered to double-
sided board;
free air
V
Output leakage current
Short-circuit voltage (AD8xx/AD9xx only)
Except AD8xx/AD9xx
Regulator output
AD8xx/AD9xx
Regulator output current (AD4xx – AD9xx)
Frequency response
Junction–Ambient Thermal Resistance
μA
V
V
V
mA
kHz
0.17
6.2
6
320
°C/W
NVE Corporation
11409 Valley View Road, Eden Prairie, MN 55344-3617
Phone: (952) 829-9217
sensor-info@nve.com
www.nve.com
©NVE Corporation
AD-Series GMR Switches
Operation
Typical connections with an external pull-up resistor are shown below:
10V
Vcc
1K
OUT
GMR
Sensor
Element
Comparator
GND
ADxxx
Figure 1. Typical connections.
10
10
Output (V)
ON
OFF
OFF
ON
Output (V)
ON
OFF
OFF
ON
0
-40
-20
0
20
40
0
-15
-10
-5
0
5
10
15
Applied Field (Oe)
Figure 2a. Typical output vs. magnetic field
(AD024 with a 10V supply and 1 KΩ pull-up resistor).
Applied Field (Oe)
Figure 2b. Typical output vs. magnetic field
(ADH025 with a 10V supply and 1 KΩ pull-up resistor).
ON / OFF Behavior
AD-Series sensor outputs turn ON when the field exceeds the magnetic operate point, and OFF when the field drops below the
operate point minus the release differential.
External Pull-Up Resistors
Outputs are open collector, with PNP output transistors for sourcing versions and NPN transistors for sinking versions. Outputs
should have external pull-up or pull-down resistors. For microcontroller interfaces, the microcontroller’s input pull-up resistors can
be activated.
Omnipolar
GMR Switches are “omnipolar,” which means the outputs turn ON when a magnetic field of either magnetic polarity is applied.
3
NVE Corporation
11409 Valley View Road, Eden Prairie, MN 55344-3617
Phone: (952) 829-9217
sensor-info@nve.com
www.nve.com
©NVE Corporation
AD-Series GMR Switches
In-Plane Magnetic Sensitivity
As the field varies in intensity, the digital output will turn on and off. Unlike Hall-effect or other sensors, the direction of
sensitivity is in the plane of the package. The diagrams below show two permanent magnet orientations that will activate the
sensor in the direction of sensitivity:
Figure 3. Planar magnetic sensitivity.
Standard and Cross-Axis Sensitivity
Standard AD-Series sensors are sensitive along the part axis as shown in Figure 4b, but a number of versions are available with
cross-axis sensitivity (see Figure 4a).
Figure 4a.
Cross-axis sensitivity.
Figure 4b.
Standard sensitivity.
Typical Operation
A typical proximity sensor using an AD022 cross-axis sensor and magnet is shown in the figures below. This sensor has a 40 Oe
typical operate point, and actuates with the magnet approximately 0.375 inches (9 mm) from the center of the sensor. Because the
sensor is omnipolar, it will operate with either a north or south magnet face.
Figure 5. An AD022 sensor (pin 1 is upper left; the sensor has cross-axis sensitivity),
on an AG015 circuit board with a 12031 8 mm dia. x 3 mm thick ferrite magnet.
Sensor activates at approx. 9 mm distance.
Red wire = V
CC
; Blk = GND; Blue = OUT (Sink).
More sensitive sensors with lower magnetic operate points (such as the 10 Oe ADH025-00E) operate with the magnet farther
away. Stronger or larger magnets will also increase the operate distance. Our most sensitive digital sensor (the AFL006; see
AFL-Series sensor datasheet)
has been demonstrated to operate with a rare-earth magnet at an air gap of two inches (50 mm) or
more.
We have a free, Web-based application that provides fields and operate distances for various sensor and magnet types:
www.nve.com/spec/calculators.php
4
NVE Corporation
11409 Valley View Road, Eden Prairie, MN 55344-3617
Phone: (952) 829-9217
sensor-info@nve.com
www.nve.com
©NVE Corporation
AD-Series GMR Switches
Illustrative Application Circuits
Integrated Short-Circuit Protection
AD8xx and AD9xx models include integrated Short Circuit Protection (“SCP”) circuitry. A detailed block diagram of such a
device is shown below:
AD924-00
C2
Vcc
C1
ShortL
Source
Sink1
GND
a. Comparator
b. SCP Turn-On Delay Timer
c. Off-State Timer
d. GMR Bridge
e. Comparator
Vreg
Figure 5. Detailed block-diagram of the AD924
sensor with short-circuit protection circuitry.
Typical SCP external circuitry for sourcing and sinking SCP versions are shown in the following schematics:
Vcc
C2
1
C1
2
Vcc
8
ShortH
7
R
BIAS1
R
SHORT
AD821-00
Sink2
3
GND
4
Sink1
6
Vreg
5
R
BIAS2
2N2907
R
LED
C
2
C
1
Output
Figure 6. Short-circuit protection circuitry (sourcing output).
5
NVE Corporation
11409 Valley View Road, Eden Prairie, MN 55344-3617
Phone: (952) 829-9217
sensor-info@nve.com
www.nve.com
©NVE Corporation
