KMA199_1

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© NXP B.V. 2010. All rights reserved.

Product data sheet

Rev. 01 — 26 April 2010

4 of 36

NXP Semiconductors

KMA199

Programmable angle sensor

5.

Functional description

The KMA199 amplifies two orthogonal differential signals which are delivered by 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. Thus, the output is 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, like

sample identification.

The KMA199 comprises a Cyclic Redundancy Check (CRC) and an Error Detection and

Correction (EDC) supervision, as well as a magnet-loss detection to ensure a fail-safe

operation. A power-loss detection circuit pulls the analog output to the remaining supply

line, if either the supply voltage or the ground line is interrupted.

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

includes offset cancellation, 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 are stored in an user-programmable EEPROM. The OWI

(accessible using pin OUT/DATA) is used for accessing the memory.

5.1 Angular measurement directions

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

In order to obtain a correct output signal, the minimum saturation field strength has to be

exceeded.