MLX90316
Rotary Position Sensor IC
3901090316
Page 9 of 41
Data Sheet
Rev. 003
April 07
Those Hall signals are processed through a fully differential analog chain featuring the classic offset
cancellation technique (Hall plate quadrature spinning and chopper-stabilized amplifier).
The conditioned analog signals are converted through an ADC (configurable
− 14 or 15 bits) 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 angular position from the two raw signals (after so-called front-end
compensation steps) through the following operation:
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
=
X
Y
V
V
ATAN
α
The DSP functionality is governed by the micro-code (firmware
− F/W) of the micro-controller which is
stored into the ROM (mask programmable). In addition to the
″ATAN″ function, the F/W controls the whole
analog chain, the output transfer characteristic, the output protocol, the programming/calibration and also
the self-diagnostic modes.
In the MLX90316, the
″ATAN″ function is computed via a look-up table (i.e. it is not obtained through a
CoRDiC algorithm).
Due to the fact that the
″ATAN″ operation is performed on the ratio ″VY/VX″, the angular information is
intrinsically self-compensated vs. flux density variations (due to airgap change, thermal or ageing effects)
affecting both signals. This feature allows therefore an improved thermal accuracy vs. rotary position
sensor based on conventional linear Hall sensors.
In addition to the improved thermal accuracy, the realized rotary position sensor is capable of measuring a
complete revolution (360 Degrees) and the linearity performances are excellent taking into account typical
manufacturing tolerances (e.g. relative placement between the Hall IC and the magnet).
Once the angular information is computed (over 360 degrees), it is further conditioned (mapped) vs. the
target transfer characteristic and it is provided at the output(s) as:
•
an analog output level through a 12 bit DAC followed by a buffer
•
a digital PWM signal with 12 bit depth (programmable frequency 100 Hz
… 1 kHz)
•
a digital Serial Protocol (SP
− 14 bits computed angular information available)
For instance, the analog output can be programmed for offset, gain and clamping to meet any rotary
position sensor output transfer characteristic:
Vout(
α) = ClampLo
for
α ≤ αmin
Vout(
α) = Voffset + Gain × α
for
αmin ≤ α ≤ αmax
Vout(
α) = ClampHi
for
α ≥ αmax
where Voffset, Gain, ClampLo and ClampHi are the main adjustable parameters for the end-user.
The linear part of the transfer curve can be adjusted through either a 2 point or a 3 point calibration
depending on the linearity requirement.
A digital output is also available and used as a programmable angular switch.
The calibration parameters are stored in EEPROM featuring a Hamming Error Correction Coding (ECC).
The programming steps do not require any dedicated pins. The operation is done using the supply and
output nodes of the IC. The programming of the MLX90316 is handled at both engineering lab and
production line levels by the Melexis Programming Unit PTC-04 with the dedicated MLX90316
daughterboard and software tools (DLL
− User Interface).
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