KMA220 datasheet(4/36 Pages) NXP

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KMA220

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Product data sheet

Rev. 1 — 24 May 2012

4 of 36

NXP Semiconductors

KMA220

Dual channel programmable angle sensor

Functional description

Each channel of the KMA220 amplifies two orthogonal differential signals from MR sensor

bridges and converts them into the digital domain. The angle is calculated using the

COordinate Rotation DIgital Computer (CORDIC) algorithm. After a digital-to-analog

conversion, the analog signal is provided to the output as a linear representation of the

angular value. Zero angle, clamping voltages and angular range are programmable.

In addition, two 16-bit registers are available for customer purposes, such as sample

identification.

Each channel of the KMA220 comprises a Cyclic Redundancy Check (CRC) and an Error

Detection and Correction (EDC), as well as magnet-loss to ensure a fail-safe operation.

If either the supply voltage or the ground line of the mixed signal IC is interrupted,

a power-loss detection circuit pulls the analog output to the remaining connection.

After multiplexing the two MR Wheatstone bridge signals and their successive

amplification, the signal is converted into the digital domain by an Analog-to-Digital

Converter (ADC). Further processing is done within an on-chip state machine. This state

machine controls offset cancelation, calculation of the mechanical angle using the

CORDIC algorithm, as well as zero angle and angular range adjustment. The internal

Digital-to-Analog Converter (DAC) and the analog output stage are used for conversion of

the angle information into an analog output voltage, which is ratiometric to the supply

voltage.

The configuration parameters of each channel are stored independently in a

user-programmable non-volatile memory. The OWI (accessible using pin OUTn/DATAn) is

used for accessing the memory. In order to protect the memory content a lock bit can be

set. After locking the non-volatile memory, its content cannot be changed anymore.

5.1 Angular measurement directions

The differential signals of the MR sensor bridges depend only on the direction of the

external magnetic field strength Hext, which is applied parallel to the plane of the sensor.

In order to obtain a correct output signal, exceed the minimum saturation field strength.

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