MA704 – 10-BIT, DIGITAL ANGLE SENSOR WITH ABZ & UVW OUTPUTS
In general, the MagAlpha works well with or
without the exposed pad connected to anything.
For optimum conditions (electrically, thermally,
and mechanically), it is recommended that the
exposed pad be connected to ground.
Serial Interface
The sensor supports the SPI serial interface for
Figure 4: End-of-Shaft Mounting
angle reading and register programming.
Alternatively, the SSI bus can be used for angle
reading (programming through SSI is not
supported).
If the end-of-shaft position is not available, the
sensor can be positioned away from the rotation
axis of a cylinder or ring magnet (see Figure 5).
In this case, the magnetic field angle is no longer
directly proportional to the mechanical angle.
The MA704 can be adjusted to compensate for
this effect and recover the linear relation
between the mechanical angle and the sensor
output. With multiple pole pair magnets, the
MA704 indicates multiple rotations for each
mechanical turn.
SPI
SPI is
a
four-wire, synchronous, serial
communication interface. The MagAlpha
supports SPI Mode 3 and Mode 0 (see Table 1
and Table 2). The SPI Mode (0 or 3) is detected
automatically by the sensor and therefore does
not require any action from the user. The
maximum clock rate supported on SPI is 25MHz.
There is no minimum clock rate. Note that real-
life data rates depend on the PCB layout quality
and signal trace length. See Figure 7 and Table
3 for SPI timing.
All commands to the MagAlpha (whether for
writing or reading register content) must be
transferred through the SPI MOSI pin and must
be 16-bit long. See the SPI Communication
section on page 13 for details.
Figure 5: Side-Shaft Mounting
Electrical Mounting and Power Supply
Decoupling
It is recommended to place a 1µF decoupling
capacitor close to the sensor with a low
impedance path to GND (see Figure 6).
Table 1: SPI Specification
Mode 0
Low
Mode 3
High
SCLK idle state
Data capture
On SCLK rising edge
On SCLK falling edge
High
3.3 V
Data transmission
CS idle state
MGL MGH
VDD
A
B
Z
Data order
MSB first
MISO
MOSI
SCLK
CS
Table 2: SPI Standard
Mode 0
Mode 3
1 mF
CPOL
CPHA
0
1
1
MA704
GND
0
SSCK
Data Order (DORD)
0 (MSB first)
SSD
Exposed pad
TEST
PWM
Figure 6: Connection for Supply Decoupling
MA704 Rev. 1.0
9/27/2017
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