AAT001-10E - NVE CORPORATION - Datasheet.Directory

AAT00x Angle Sensors

NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.nve.com ©NVE Corporation

AAT00x Ultralow Power TMR Angle Sensors

Functional Diagram

Sin

Vcc

GND

Cos

Vcc

GND

Features

• Tunneling Magnetoresistance (TMR) technology

• Sub-microwatt power consumption

• High output signal without amplification

• Immune to airgap variations

• Operates with as little as 30 Oersted field

• Sine and cosine and outputs

• −40°C to +125°C operating temperature

• Ultraminiature TDFN6 packages

Applications

• Battery-powered applications

• Knob position sensors

• Rotary encoders

• Automotive rotary position sensors

• Motor shaft position sensors

Description

AAT00x angle sensors use unique Tunneling

Magnetoresistance (TMR) elements for large signals and

low power consumption.

The sensors provide sine and cosine signals defining the

angle of rotation. Outputs are proportional to the supply

voltage and peak-to-peak output voltages are much larger

than conventional sensor technologies.

AAT00x sensors consist of two half-bridges. The AAT001

has a typical bridge resistance of 1.25 MΩ for ultra-low

power, and the AAT009 has a bridge resistance of 6 MΩ for

ultra-ultra-low power.

Parts are packaged in NVE’s 2.5 mm x 2.5 mm x 0.8 mm

TDFN6 surface-mount package.

AAT00x Angle Sensors

NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.nve.com ©NVE Corporation

Absolute Maximum Ratings

Parameter Min. Max. Units

Supply voltage 7 Volts

Reverse supply voltage −12 Volts

Storage temperature −40 170 °C

ESD (Human Body Model) 2000 Volts

Applied magnetic field Unlimited1 Oe

Operating Specifications

Parameter Symbol Min. Typ. Max. Units Test Condition

Operating temperature Tmin; Tmax −40 125 °C

Device resistance 25°C with required

magnetic field.

AAT001 0.6 1.25 2.5 MΩ

AAT009 4 6 10 MΩ

Peak-to-peak output signal VPP-SIN

VPP-COS 130 200 mV/V Over full rotation.

Offset voltage VOFFSET-SIN

VOFFSET-COS −10 +10 mV/V

Supply voltage VCC 0 5.5 V

Required applied magnetic field 30 200 Oe

Repeatability, fixed bias2 ±0.5 deg.

Repeatability, variable bias3 ±3 deg.

Nonsinusoidality4 ±1.5%

% of peak-to-peak output;

50 Oe applied field; 25°C

Temperature coefficient of resistance TCOR +0.09

%/°C

Output voltage temperature coefficient TCOV −0.13

%/°C Constant

supply voltage.

Notes:

1. Large magnetic fields CANNOT damage NVE sensors.

2. “Fixed Bias” means a fixed airgap between the bias magnet and sensor so the magnetic field at the sensor is constant.

3. “Variable Bias” means the magnetic field strength at the sensor can vary across the specification range.

4. Maximum deviation of either output from an ideal sine wave.

AAT00x Angle Sensors

NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.nve.com ©NVE Corporation

Operation

Overview—Unique TMR technology

The heart of the unique sensor is an array of four Tunneling Magnetoresistance (TMR) elements 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 in the plane of the sensor, as illustrated below

for a bar magnet and a radially-magnetized disk magnet:

Figure 1. Sensor operation.

The device contains four sensing resistors at 90 degree intervals. The resistors are connected as two half-bridges, providing the

sine and cosine voltage outputs. For each half bridge, the resistance of one element increases and the other decreases as the field

rotates. Thus the bridge resistance, device resistance, and output impedances remain constant with rotation.

Transfer function

The half-bridge configuration provides a simple interface and can simplify external circuitry such as amplifiers and comparators.

Outputs are sinusoidal, centered around half the supply, and ratiometric with supply voltage. Mathematically, the outputs can be

expressed as:

VSIN = [VCC-SIN][(VSIN-MAX – VSIN-MIN) / 2)Sin θ + VCC-SIN / 2 + VOFFSET-SIN]

VCOS = [VCC-COS][(VCOS-MAX – VCOS-MIN) / 2)Cos θ + VCC-COS / 2 + VOFFSET-COS]

Where:

θ is the magnetic field angle;

VCOS and VSIN are the sensor output voltages (mV/V);

VCC-SIN and VCC-COS are the sensor supply voltages (normally tied together);

VSIN-MAX, VCOS-MAX, VSIN-MIN, and VCOS-MIN are the sensor output peak signal levels (mV/V); and

VOFFSET-SIN and VOFFSET-COS are the sensor offset voltages (mV/V),

defined as the average of the maximum and minimum outputs minus half the supply voltage.

Wide range of magnets and magnet locations

The sensors operate with fields from 30 Oe 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

in production. Bar magnets are also used in some configurations.

AAT00x Angle Sensors

NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.nve.com ©NVE Corporation

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

024

48 72 96 120 144 168 192 216 240 264 288 312 336 360

Degrees of Rotation

oltage

Cosine, 3mm

Sine, 3mm

Cosine, 4mm

Sine, 4mm

Cosine, 5mm

Sine, 5mm

Ideal for battery and harvested power

AAT-Series sensors are resistive devices with no active components, so they have no minimum voltage and can be powered from

single cells. With their low power, the sensors are well-suited for operation from batteries or harvested power, and can run

continuously for many years on small alkaline, silver oxide, or lithium button cells.

The following chart shows a typical sensor output versus the angle of applied field at different air gaps:

Figure 2. AAT001 Typical Output with Variations in Airgap

(5V supply; 12 mm diameter, 4 mm thick split-pole ferrite magnet; 5 V supply).

Ideal for battery and harvested power

AAT-Series sensors are resistive devices with no active components, so they have no minimum voltage and can be powered from

single cells. With their low power, the sensors are well-suited for operation from batteries or harvested power. The AAT009 is

especially ideal for such applications because of its extremely high bridge resistance. AAT009 sensors can run continuously for

many years on small alkaline, silver oxide, or lithium button cells.

Harvested power is often intermittent, and AAT-Series sensors detect and maintain absolute position information. The sensors

immediately powers up indicating the correct position after power is restored.

One cycle per revolution

Other sensor types such as AMR have two cycles per revolution, so they cannot determine absolute position for 360-degree

rotation. AAT-Series sensors output one cycle per revolution and can unambiguously determine position within a full rotation.

Detects absolute position

Unlike some encoder types, AAT-Series sensors detect absolute position, and maintain position information when power is

removed. The sensor immediately powers up indicating the correct position.

AAT00x Angle Sensors

NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.nve.com ©NVE Corporation

Application Circuitry

External comparators

A dual comparator can provide digital outputs from AAT angle sensors. Low-power comparators and large resistors are used to

avoid adding power consumption to low-power applications:

R1 (Sine) Sin

Vcc

GND

R2 (Sine)

R4 (Cosine)

R3 (Cosine)

Cos

Vcc

GND

100 nF 5M

AAT00x Sensor

3.3 V

MCP

6542

Rotation

360˚

0 90˚180˚270˚

Sgn(Cos) Sgn(Sin)

Figure 2. External dual comparator for digital outputs.

Inherent comparator hysteresis eliminates noise at the transition points. The MCP6542 comparator hysteresis of 3.3 mV

corresponds to about 1 angular degree of hysteresis. Higher hysteresis comparators can be used for more noise immunity at the

expense of hysteresis.

NVE also offers ADT-Series sensors that include integrated comparators to replicate the circuit of Figure 2.

Quadrant outputs

A 2-to-4 line decoder can provide digital signals to indicate the quadrant of rotation:

R1 (Sine) Sin

Vcc

GND

R2 (Sine)

R4 (Cosine)

R3 (Cosine)

Cos

Vcc

GND

100 nF 5M

AAT00x Sensor

3.3 V

SN74LV

C1G139

MCP

6542

750

0˚-90˚

90˚-180˚

180˚-270˚

270˚-360˚

Figure 3. Digital Quadrant Outputs.

AAT00x Angle Sensors

NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.nve.com ©NVE Corporation

Speed and direction signals

Commodity CMOS circuits can be added to create a precise encoder with direction and speed outputs. A flip-flop determines

direction by detecting the phasing between the two outputs. An exclusive-OR gate provides a digital signal with two cycles per

revolution, and transitions every 90 degrees:

R1 (Sine) Sin

Vcc

GND

R2 (Sine)

R4 (Cosine)

R3 (Cosine)

Cos

Vcc

GND

100 nF 5M

AAT00x Sensor

Speed

(2/rev)

7SZ86

3.3 V

SN74

AUP1G79

CLK

Direction

TLV

3502

360˚270˚180˚

090˚

Figure 4. Speed and direction signals.

Rotation reference signals

An AAT angle sensor and a single comparator can provide a precise angular reference point and a one cycle-per-rotation signal.

Comparing the sine and cosine outputs is more precise than comparing either to a reference because it corrects for temperature.

AAT00x Sensor

R1 (Sine) Sin

Vcc

GND

R2 (Sine)

R4 (Cosine)

R3 (Cosine)

Cos

Vcc

GND

100 nF

0.9 to 5.5 V

TLV3691

OUT

360˚

Sin

Cos

OUT

45˚ 225˚

Figure 5. Angular Reference Point Rotation Signal.

In this circuit, the output is high from nominal 45 to 225 degrees, and low from 225 to 45 degrees. A low voltage, low quiescent

current comparator is used to preserve the AAT sensors’ ultra-low power and wide supply range. Inherent comparator hysteresis

eliminates noise at the transition points. The TLV3691 comparator hysteresis of 17 mV corresponds to approximately 6 degrees of

hysteresis with a 1.5 V supply. A TS881 or similar comparator has a typical hysteresis of 4 mV, corresponding to 1.5 angular

degrees of hysteresis.

AAT00x Angle Sensors

NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.nve.com ©NVE Corporation

Low-power amplification

AAT-Series sensors have high output signals without amplification, but if amplification is required, a circuit like the one below

can be used. The 10 megohm resistors and nanopower TLV522 op-amp minimize the added power consumption of the amplifier.

A gain of three amplifies the sensor’s typical peak-to-peak signal level of 200 mV/V to 60% of rail-to-rail (one volt/volt),

providing more usable signal without risk of saturating the amplifier for a sensor at the high end of the output signal range:

AAT00x Sensor

R1 (Sine) Sin

Vcc

GND

R2 (Sine)

R4 (Cosine)

R3 (Cosine)

Cos

Vcc

GND

3Sin

3Cos

TLV522

100 nF

1.7 V

to 5.5 V

10M

2x 10 pF

Figure 6. 3x Preamplifier.

Although AAT00x sensors are designed to be used primarily as two half bridges, if quadrature outputs are not required, a similar

differential amplifier circuit can provide a larger signal, more precision, and less temperature dependence than either the sine or

cosine output alone:

AAT00x Sensor

R1 (Sine) Sin

Vcc

GND

R2 (Sine)

R4 (Cosine)

R3 (Cosine)

Cos

Vcc

GND

100 nF

5 V

INA826

360˚

Sin-Cos

OUT

45˚ 225˚

RG=33K

(Gain = 2.5)

REF

100K

100 pF

(Vp-p)

Figure 7. 2.5x Differential Amplifier.

The differential (VSIN − VCOS) voltage has an amplitude of 1.41 times the amplitude of either output, or typically 282 mV/V peak-to-

peak. Therefore the amplifier gain of 2.5 provides a typical peak-to-peak output of 71% of rail-to-rail (one volt/volt). Note that the

zero crossing is at 45 degrees, versus to 0 degrees for the Sin output and 90 degrees for the Cos output. An instrumentation

amplifier can be used to minimize parts count when power consumption is not critical.

AAT00x Angle Sensors

NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.nve.com ©NVE Corporation

Noise mitigation

High-impedance circuitry is inherently susceptible to noise. Common noise mitigation steps include:

• Power supply decoupling capacitors near the sensor (100 nF typical).

• Limiting the sensor output bandwidth to only what is needed. Because the sensor outputs are resistive, filter capacitors can

be connected directly to the outputs. The sensor output impedances are half the bridge resistance, so the cutoff frequency

is:

fc = 1/(π RB C)

where RB is the bridge resistance and C is the output capacitance.

• Digital filtering or averaging in microcontroller systems.

External comparator considerations

Low voltage, low quiescent current comparators are generally used to preserve the AAT sensors’ ultra-low power and wide supply

range.

Some hysteresis in external comparators is desirable to reduce noise and jitter at transition points. Too much hysteresis, however,

may cause undesirable errors. Low-hysteresis comparators are especially important in low voltage applications, since hysteresis is

a larger portion of the signals. Angular hysteresis relates to comparator hysteresis as follows:

(360/π)(VHC)

(VCC)(VPP)

Where:

θH the angular hysteresis in degrees;

VHC is the comparator’s hysteresis;

VCC is the sensor power supply; and

VPP is the sensor’s peak-to-peak sensitivity (typically 200 mV/V).

For example, MCP6542 comparators have hysteresis of 3.3 mV, corresponding to about 1 angular degree of hysteresis. TLV3691

or similar comparators have hysteresis of 17 mV, corresponding to approximately 6 degrees of hysteresis with a 1.5 V supply.

Ultralow power external CMOS

Any of the application circuits described in this section can use 74AUP-family logic rather than 74LVC if lower power is required

and five-volt operation is not needed.

θH =

AAT00x Angle Sensors

NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.nve.com ©NVE Corporation

Pinout

Sin

Vcc

GND

Cos

Vcc

GND

0˚

AAT00x

Pin Symbol Description

1 VCC-COS Supply voltage (up to 5.5 V) for the Cos sensor elements.

2 Cos Corresponds to the cosine of the rotation angle.

3 GND Ground for the Cos sensor elements.

4 GND Ground for the Sin sensor elements.

5 Sin Corresponds to the sine of the rotation angle.

6 VCC-SIN Supply voltage for the Sin sensor elements.

Notes:

• Clockwise rotation as viewed from the top of the package is interpreted as increasing angle.

• The package center pad may be left floating or connected to ground.

• This product has been tested for electrostatic sensitivity to the limits stated in the specifications. However, NVE recommends that all

integrated circuits be handled with appropriate care to avoid damage. Damage caused by inappropriate handling or storage could range

from performance degradation to complete failure.

Available Parts

Part

Number

Typ. Bridge

Resistance Marking

AAT001-10E 1.25 MΩ FCVe

AAT009-10E 6 MΩ FDZe

AAT00x Angle Sensors

NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.nve.com ©NVE Corporation

2.5 mm x 2.5 mm TDFN6 Package

2.00 ± 0.05

C0.10

PIN 1

0.30±0.05

0.30±0.05 0.65 TYP.

1.30 REF (2X)

2.50 ± 0.10

2.50±0.10

0.0-0.05

0.80 MAX.

0.20 REF

1.30±0.05

(6X) (4X)

Notes:

• Dimensions in millimeters.

• Soldering profile per JEDEC J-STD-020C, MSL 1.

RoHS

COMPLIANT

AAT00x Angle Sensors

NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.nve.com ©NVE Corporation

Revision History

April 2017 Changes

• Clarified repeatability vs. accuracy (p. 2).

• Added nonsinusoidality specification (p. 2).

• Lower-power amplifier circuit (p. 7).

November 2016 Changes

• Split out AAT003 into a separate datasheet.

• Revised applications section.

June 2016 Changes

• Consolidated AAT001, AAT003, and AAT009 datasheets.

• Added application circuits.

• Added microcontroller interface application section.

AAT00x Angle Sensors

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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Applications described in this datasheet are illustrative only. NVE makes no representation or warranty that such applications will be suitable for the

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Stress above one or more limiting values (as defined in the Absolute Maximum Ratings System of IEC 60134) will cause permanent damage to the

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AAT00x Angle Sensors

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SB-00-024_AAT00x-10E

April 2017