MLX90363 Datasheet, PDF (7/57 Pages) Melexis Microelectronic Systems – Triaxis® Magnetometer IC With High Speed Serial Interface

MLX90363
Triaxis® Magnetometer IC
With High Speed Serial Interface
7. Detailed Description
The three components of the applied flux density are measured through the Tria⊗is front end:
VX ∝ BX
VY ∝ BY
VZ ∝ BZ
Those three (3) Hall voltages corresponding to the three (3) components of the applied flux density are
provided to the ADC (Analog-to-Digital Converter). The Hall signals are processed through a fully
differential analog chain featuring the classic offset cancellation technique (Hall plate 2-Phases spinning
and chopper-stabilized amplifier).
The amplitude of VZ is smaller than the two (2) components VX and VY due to the fact that the magnetic
gain of the IMC only affects the components parallel to the IC surface.
The conditioned analog signals are converted through a 14 bit ADC and provided to a DSP block for
further processing. The DSP stage is based on a 16 bit RISC micro-controller whose primary function is
the extraction of the position information (magnetic angle(s)) from the raw signals (after front-end
compensation steps) through one the following operations:
α
=
ATAN _{}
k ⋅V₁
V₂

where V1 = VX or VY or VZ , V2 = VX or VY or VZ and k (or SMISM) is a programmable factor to match the
amplitude of k V1 and V2.
α = ATAN_{}
(k_αV₃ )² + (k_tV₂ )²
V₁


and
β
=
ATAN



(k_βV₃ )² + (k_tV₁)² _
V₂


where V1 = VX or VY or VZ, V2 = VX or VY or VZ, V3 = VX or VY or VZ and k_α, k_β and k_t are programmable
parameters.
The DSP functionality is governed by the micro-code (firmware − FW) of the micro-controller which is
stored into the ROM (mask programmable). In addition to the “ATAN” (“Arctangent”) function, the FW
controls the whole analog chain, the programming/calibration and also the self-diagnostic modes.
Due to the fact that the “ATAN” operation is performed on the ratios “V1/V2”, “V3/V1” and “V3/V2”, the
output is intrinsically self-compensated vs. flux density variations (due to airgap change, thermal or ageing
effects) affecting both signals. This feature allows an improved thermal accuracy compared to a
conventional linear Hall sensor.
The end-user programmable parameters are stored in EEPROM featuring a Hamming Error Correction
Coding (ECC).
The programming steps do not require dedicated pins or programming tool. The operation is performed
through the Master and the Serial Protocol using a dedicated and protected function⁽³⁾.
3 _{For debug/demo purpose, Melexis can provide the Melexis Programming Unit PTC-04 with the SPI daughterboard (PTC-04-DB-}
SPI) and software library (PSF – Product Specific Functions).
3901090363
Rev. 005
Page 7 of 57
Data Sheet
Jul/13