KMA321 datasheet(4/71 Pages) NXP

4 / 71 page

NXP Semiconductors

KMA321

Programmable angle sensor IC

KMA321

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Product data sheet

Rev. 3 — 28 January 2019

4 / 71

6 Functional description

The KMA321 converts two orthogonal signals from MR sensor bridges 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 or transmitted in a SENT frame compliant

to SAE J2716. Zero angle, clamping voltages and angular range are programmable. In

addition, eight 12-bit registers are available for customer purposes, such as sample ID.

KMA321 comprises a cyclic redundancy check (CRC) and an error detection code (EDC)

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 output to the remaining

connection.

After conversion into the digital domain by an 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. Alternatively, the output signal can be transmitted

digitally in a SENT frame compliant to SAE J2716.

The configuration parameters are stored in a user-programmable non-volatile memory.

The OWI (accessible using pin OUT/DATA) 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.

6.1 Angular measurement directions

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

magnetic field vector 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.

aaa-029947

Hext

Figure 2. Angular measurement directions

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