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6
ROTARY-HUMAN-MACHINE-INTERFACE APPLICATIONS
6
Magnetic Angular Position Sensor Solutions
Q3 2018
Rotary knobs are used in a diversity of hu-
man-to-machine-interface applications, such
as the program selector on a washing machine
or the infotainment control in a car. These appli-
cations typically use a conventional potentiom-
eter or mechanical rotary applications, which
have limited life spans due to mechanical wear
and tear or environmental degradation. The use
of magnetic angle sensors to implement con-
tactless sensing eliminates both issues to pro-
vide a long lifetime solution.
The MagAlpha MA8xx family is a new, simple-to-
use, digital, magnetic sensor range designed to
replace analog potentiometers or rotary switch-
es in such applications. The sensor detects the
absolute angular position of a permanent magnet
attached to the rotating knob. Typically, a simple di-
ametrically magnetized cylinder with a 3 to 8mm di-
ameter is suitable.
Different options are available, including digital angle
output via SPI/SSI bus, incremental ABZ interface, or
PWM output.
Programmable threshold magnetic field strength de-
tection is built in to enable implementation of a con-
tactless push or pull button. Detection is performed
by reading the device registers or the logic state of
the two output signals. In this way, a combined rotary
knob with “push or pull to select” functionality can be
created.
MA8xx
NVM Registers
Spinaxis front-end
2D Hall effect
device
BP
Phase
detection
Amplitude
detection
ABZ
Encoder
Digital
Conditioning
PWM
Serial
interface
VDD
CS
SCLK
MISO
MOSI
SSCK
SSD
PWM (MA850)
A
B (MA820)
Z
MGL
MGH
GND
Figure 2: Block Diagram of MA8xx Family Sensor
Rotary Human-Machine-Interface Applications
MA8xx Family