MLX90333 View Datasheet(PDF) - Unspecified

Part Name

Description

Manufacturer

MLX90333

Triaxis 3D-Joystick Position Sensor

Unspecified 

MLX90333

Triaxis 3D-Joystick Position Sensor

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 two (2) angular information from the three (3) raw signals (after so-

called front-end compensation steps) through the following operations:

α

=

ATAN ⎜⎜⎝⎛

VX

kZVZ

⎟⎟⎠⎞

β

=

ATAN

⎜⎜⎝⎛

VY

kZVZ

⎟⎟⎠⎞

where kZ is a programmable parameter.

In a joystick based on a “ball & socket” joint as shown on Figure 3 (right), the magnet (axial

magnetization) moves on a hemisphere centered at the pivot point. The flux density is described through

slightly more complex equations but the MLX90333 offers an alternate algorithm to extract both angular

informations:

α

=

ATAN

⎜⎛

⎜

⎝

VX

⎟⎞

(kZVZ )2

+ (ktVY )2

⎟

⎠

β

=

ATAN

⎜⎛

⎜

⎝

VY

⎟⎞

(kZVZ )2

+ (ktVX )2

⎟

⎠

where kZ and kt are programmable parameters.

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 MLX90333, 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 ratios ″VX/VZ″ and ″VY/VZ″, the angular

information are intrinsically self-compensated vs. flux density variations (due to airgap change, thermal or

ageing effects) affecting the magnetic signal. This feature allows therefore an improved thermal accuracy

vs. joystick based on conventional linear Hall sensors.

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)

3901090333

Rev. Preliminary

Page 11 of 38

Data Sheet

May 07

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