Data Sheet

ADA4571-2

Rev. 0 | Page 11 of 13

APPLICATIONS INFORMATION

The integrated AMR sensor is designed for applications with a

separate processing IC or electronic control unit (ECU) containing

a Σ-Δ ADC with references connected to the supply voltage.

as the AMR sensor output, the system is inherently ratiometric and

the signal dependency on supply voltage changes is minimized.

ANGLE CALCULATION

To calculate angle from the output of the AMR device, use the

trigonometric function, arctangent2. The arctangent2 function

is a standard arctangent function with additional quadrant

information to extend the output from the magnetic angle range

of −90° to +90° to the magnetic angle range of −180° to +180°.

Because of the sensing range of AMR technology, this calculated

magnetic angle repeats over each pole of the magnet. For a

simple dipole magnet, the following equation reports absolute

angle over 180° mechanical:

2

arctan

















COS

SIN

V

V

CONNECTION TO ECU

Because of the limited driving capability of the ADA4571-2

output, minimize the length of printed circuit board (PCB)

traces between the ADA4571-2 and other ICs. Shielding of the

signal lines is recommended. Match the load capacitors and

resistors for best angular accuracy. Add bandwidth limitation

filters related to the sampling frequency of the system in front

of the ADC inputs to reduce noise bandwidth.

The load resistors on VCOSx and VSINx are the same as the

input filter of the ADC. Use the processor for arctan and offset

calculations, offset storage, and additional calibration.

VTEMPx Output Pin

A proportional to absolute temperature circuit provides a

voltage output at the VTEMPx pin for temperature monitoring

or temperature calibration purposes. The output voltage is

ratiometric to the supply voltage, enabling the interface with an

ADC that uses the supply voltage to generate the reference

voltage. The VTEMPx pin must be left open when not in use.

To achieve maximum accuracy from the VTEMPx output

voltage, perform an initial calibration at a known, controlled

temperature. Then, use the following equation to extract

temperature information:

VTEMP

CAL

DD

CAL

DD

TEMP

VTEMP

TC

Tempco

T

V

V

V

V

T









































–

–

where:

output voltage.

controlled temperature.

Tempco is the temperature coefficient of the internal circuit; see

the Specifications section for the exact value.

Gain Control Mode

Activate gain control (GCx) enable mode by connecting the

GCx pin to the VDDx pin. In this mode, the AMR bridge sensor

amplitude outputs are compensated to reduce temperature

variation. This compensation results in higher and controlled

output voltage levels, boosts the system dynamic range, and

eases the system design task. If the GCx pin is left floating, a weak

pull-up resistor ensures that the GC mode is enabled as a default

condition. The GC mode can also be used as a sensor self

diagnostic by comparing the sine and cosine amplitude outputs

when enabled and disabled, such as a radius check. Device failure

is indicated by the radius remaining unchanged.

Power-Down Mode

Activate power-down mode by connecting the PDx pin to the

VDDx pin. In this mode, the device shuts down and the output

pins are set to high impedance to avoid current consumption

across the load resistors. The VTEMPx output is connected to

GNDx through a pull-down resistor. Enter power-down mode

ensures that the device remains active if the PDx pin is left floating.