MagAlpha MA702
12-Bit, Digital, Contactless Angle Sensor
with ABZ Incremental & PWM Outputs
DESCRIPTION
FEATURES
The MA702 detects the absolute angular
position of a permanent magnet, typically a
diametrically magnetized cylinder on a rotating
shaft. Fast data acquisition and processing
provide accurate angle measurement at speeds
from 0 to 60,000 rpm.
The MA702 supports a wide range of magnetic
field strengths and spatial configurations. Both
end-of-shaft and off-axis (side-shaft mounting)
configurations are supported.
The MA702 features magnetic field strength
detection with programmable thresholds to allow
sensing of the magnet position relative to the
sensor for creation of functions such as the
sensing of axial movements or for diagnostics.
On-chip non-volatile memory provides storage
for configuration parameters, including the
reference zero angle position, ABZ encoder
settings, and magnetic field detection
thresholds.
12-Bit Resolution Absolute Angle Encoder
Contactless Sensing for Long Life
SPI Serial Interface for Digital Angle
Readout and Chip Configuration
Incremental 10-Bit ABZ Quadrature
Encoder Interface with Programmable
Pulses Per Turn from 1-256
PWM Output 12-Bit
Programmable Magnetic Field Strength
Detection for Diagnostic Checks
3.3V, 12mA Supply
-40°C to +125°C Operating Temperature
Available in a QFN-16 (3mmx3mm)
Package
APPLICATIONS
General Purpose Angle Measurement
Angle Encoders
Automotive Angle or Speed Sensors
Robotics
All MPS parts are lead-free, halogen-free, and adhere to the RoHS directive. For
MPS green status, please visit the MPS website under Quality Assurance. “MPS”
and “The Future of Analog IC Technology” are registered trademarks of Monolithic
Power Systems, Inc.
TYPICAL APPLICATION
MA702 Rev. 1.1
2/6/2020
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
ORDERING INFORMATION
Part Number*
MA702GQ
Package
QFN-16 (3mmx3mm)
Top Marking
See Below
* For Tape & Reel, add suffix –Z (e.g. MA702GQ–Z)
TOP MARKING
AYG: Product code of MA702GQ
Y: Year code
LLL: Lot number
PACKAGE REFERENCE
TOP VIEW
QFN-16 (3mmx3mm)
MA702 Rev. 1.1
2/6/2020
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
ABSOLUTE MAXIMUM RATINGS (1)
Thermal Resistance (3)
Supply voltage ............................ -0.5V to +4.6V
Input pin voltage (VI) ................... -0.5V to +6.0V
Output pin voltage (VO) ............... -0.5V to +4.6V
Continuous power dissipation (TA = +25°C) (2)
..................................................................2.0W
Junction temperature ............................... 125°C
Lead temperature .................................... 260°C
Storage temperature .................. -65°C to 150°C
QFN-16 (3mmx3mm) ............ 50 ....... 12 ... °C/W
MA702 Rev. 1.1
2/6/2020
θJA
θJC
NOTES:
1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature TJ (MAX), the junction-toambient thermal resistance θJA, and the ambient temperature
TA. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by PD (MAX) = (TJ
(MAX)-TA)/θJA.
3) Measured on JESD51-7, 4-layer PCB.
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
ELECTRICAL CHARACTERISTICS
Parameter
Symbol Condition
Recommended Operating Conditions
Min
Typ
Max
Units
Supply voltage
VDD
3.0
3.3
3.6
V
Supply current
IDD
10.2
11.7
13.8
mA
Operating temperature
Applied magnetic field
Top
B
125
°C
mT
MA702 Rev. 1.1
2/6/2020
From -40°C to +125°C
-40
30
60
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
GENERAL CHARACTERISTICS
VDD = 3.3V, 45mT < B < 100mT, Temp = -40°C to +125°C, unless otherwise noted.
Parameter
Absolute Output – Serial
Symbol
Effective resolution
Condition
Min
Typ
Max
Units
3σ deviation of the noise
distribution
11.0
11.8
12.8
bit
0.01
850
14
0.02
980
0.03
1100
14
deg
kHz
bit
12
ms
10
µs
Noise RMS
Refresh rate
Data output length
Response Time
Power-up time (4)
Constant speed propagation
delay
Latency (4)
Filter cutoff frequency (4)
Accuracy
8
fCUTOFF
At room temperature over the full
field range
Over the full temperature range
and field range
INL at 25°C
INL between -40°C to
+125°C (5)
Output Drift
Temperature induced drift at
room temperature (5)
From 25°C to 85°C
From 25°C to 125°C
Temperature induced
variation (5)
Magnetic field induced (5)
Voltage supply induced (5)
Absolute Output - PWM
PWM frequency
PWM resolution
Incremental Output – ABZ
0.7
deg
1.1
deg
0.015
0.04
deg/°C
0.5
1.0
1.2
2.1
deg
deg
0.3
deg/mT
deg/V
fPWM
204
11.0
264
12.0
Hz
bit
240
11.8
16
Resolution - edges per turn
Pulses per channel per turn
ABZ hysteresis (5)
(5)
Random jitter (3σ)
Overall ABZ jitter (5)
MA702 Rev. 1.1
2/6/2020
Hz
0.005
ABZ update rate
Systematic jitter
390
PPT+1
H
Programmable
Programmable
4
1
For PPT = 255, between 0 and
100krpm, up to 60mT
For PPT = 127, between 0 and
100krpm
For PPT = 255, between 0 and
100krpm
For PPT = 127, between 0 and
100krpm
Up to 60mT
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MHz
1024
256
0.7
deg
13
%
7
%
5.5
%
2.8
%
0.3
deg
5
MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
GENERAL CHARACTERISTICS (continued)
VDD = 3.3V, 45mT < B < 100mT, Temp = -40°C to +125°C, unless otherwise noted.
Parameter
Symbol Condition
Magnetic Field Detection Thresholds
Accuracy (5)
Hysteresis (5)
Temperature drift (5)
Digital I/O
Min
Typ
Max
5
6
-600
MagHys
mT
mT
ppm/°C
VIH
VIL
VOL
VOH
RPD
IOL = 4mA
Rising edge slew
rate (4)
TR
CL = 50pF
0.7
V/ns
Falling edge slew
rate (4)
TF
CL = 50pF
0.7
V/ns
Input high voltage
Input low voltage
Output low
voltage (5)
Output high voltage
(5)
Pull-down resistor
2.5
-0.3
Units
IOH = 4mA
2.4
43
5.5
0.8
0.4
V
V
V
V
55
97
kΩ
NOTES:
4) Guaranteed by design.
5) Guaranteed by characteristic test.
MA702 Rev. 1.1
2/6/2020
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
TYPICAL CHARACTERISTICS
VDD = 3.3V, Temp = 25°C, unless otherwise noted.
ABZ Jitter at PPT = 255
Noise Spectrum at 50mT
Filter Transfer Function
5
6
FILTER TRANSFER FUNCTION (dB)
0.01
1/2
NOISE DENSITY (deg/Hz )
RANDOM JITTER (%)
5
4
3
0.001
0
-3 dB
-5
-10
-15
2
-20
0.0001
1
0.1
1
10
100
1000
10
4
10
10
10
5
100
1000
10
4
10
100
1000
10
4
10
5
5
f (Hz)
FREQUENCY (Hz)
ROTATION SPEED (rpm)
Non-Linearity (INL and
Harmonics)
Error Curves at 50mT
Effective Resolution (3σ)
1.5
12
2
11.5
-45°C
0
EFFECTIVE RESOLUTION (bit)
NON-LINEARITY (deg)
ERROR (deg)
INL
25°C
125°C
1
1
H1
0.5
-1
H2
11
10.5
10
9.5
9
8.5
-2
8
0
0
50
100
150
200
250
300
350
0
20
40
60
80
100
0
20
40
60
80
100
120
MAGNETIC FIELD (mT)
ANGLE (deg)
MAGNETIC FIELD (T)
Current Consumption at
VDD = 3.3V
12
SUPPLY CURRENT (mA)
11.5
11
10.5
10
-50
0
50
100
150
TEMPERATURE (°C)
MA702 Rev. 1.1
2/6/2020
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
PIN FUNCTIONS
Package
Pin #
Name
1
2
SSD
A
Data out (SSI).
Incremental output.
3
4
5
6
Z
MOSI
CS
B
7
MISO
8
9
GND
PWM
Incremental output.
Data in (SPI). MOSI has an internal pull-down resistor.
Chip select (SPI). CS has an internal pull-up resistor.
Incremental output.
Data out (SPI). MISO has an internal pull-down resistor that is enabled at a high impedance
state.
Supply ground.
PWM output.
10
11
12
13
14
15
16
TEST
MGL
SCLK
VDD
NC
SSCK
MGH
Connect to ground.
Digital output indicating field strength below MGLT level.
Clock (SPI). SCLK has an internal pull-down resistor.
Supply 3.3V.
No connection. Leave NC unconnected.
Clock (SSI). SSCK has an internal pull-down resistor.
Digital output indicating field strength above MGHT level.
MA702 Rev. 1.1
2/6/2020
Description
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
BLOCK DIAGRAM
Figure 1: Functional Block Diagram
MA702 Rev. 1.1
2/6/2020
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & UVW OUTPUTS
OPERATION
Sensor Front-End
The magnetic field is detected with integrated
Hall devices located in the center of the package.
The angle is measured using the SpinaxisTM
method, which digitizes the direction of the field
directly without complex arctangent computation
or feedback loop-based circuits (interpolators).
The SpinaxisTM method is based on phase
detection and generates a sinusoidal signal with
a phase that represents the angle of the
magnetic field. The angle is then obtained by a
time-to-digital converter, which measures the
time between the zero crossing of the sinusoidal
signal and the edge of a constant waveform (see
Figure 2). The time-to-digital is output from the
front-end to the digital conditioning block.
Top: Sine Waveform
Bottom: Clock of Time-to-Digital Converter
Figure 2: Phase Detection Method
The output of the front-end delivers a digital
number proportional to the angle of the magnetic
field at the rate of 1MHz in a straightforward and
open-loop manner.
Digital Filtering
The front-end signal is further treated to achieve
the final effective resolution. This treatment does
not add any latency in steady conditions. The
filter transfer function can be calculated with
Equation (1):
H ( s)
1 2s
(1 s) 2
(1)
Where τ is the filter time constant related to the
cutoff frequency by: τ = 0.38 / fCUTOFF. See the
General Characteristics table on page 5 for the
value of fCUTOFF.
multiple integrated Hall devices. This volume is
located both horizontally and vertically within
50µm of the center of the QFN package. The
sensor detects the angle of the magnetic field
projected in a plane parallel to the package’s
upper surface. This means that the only relevant
magnetic field is the in-plane component (X and
Y components) in the middle point of the
package.
By default, when looking at the top of the
package, the angle increases when the magnetic
field rotates clockwise. Figure 3 shows the zero
angle of the unprogrammed sensor, where the
cross indicates the sensitive point. Both the
rotation direction and the zero angle can be
programmed.
Figure 3: Detection Point and Default Positive
Direction
This type of detection provides flexibility for the
design of an angular encoder. The sensor only
requires the magnetic vector to lie essentially
within the sensor plane with a field amplitude of
at least 30mT. Note that the MA702 can work
with fields smaller than 30mT, but the linearity
and resolution performance may deviate from
the specifications. The most straightforward
mounting method is to place the MA702 sensor
on the rotation axis of a permanent magnet (i.e.
a diametrically magnetized cylinder) (see Figure
4). The recommended magnet is a Neodymium
alloy (N35) cylinder with dimensions Ø5x3mm
inserted into an aluminum shaft with a 1.5mm air
gap between the magnet and the sensor
(surface of package). For good linearity, the
sensor is positioned with a precision of 0.5mm.
Sensor – Magnet Mounting
The sensitive volume of the MA702 is confined
in a region less than 100µm wide and has
MA702 Rev. 1.1
2/6/2020
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & UVW OUTPUTS
In general, the MagAlpha works well with or
without the exposed pad connected. For
optimum conditions (electrically, thermally, and
mechanically), it is recommended that the
exposed pad be connected to ground.
Figure 4: End-of-Shaft Mounting
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 MA702 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
MA702 indicates multiple rotations for each
mechanical turn.
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).
3.3 V
MGL MGH
A
B
VDD
Z
MISO
MOSI
1 mF
Serial Interface
The sensor supports the SPI serial interface for
angle reading and register programming.
Alternatively, the SSI bus can be used for angle
reading (programming through SSI is not
supported).
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 reallife 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.
Table 1: SPI Specification
SCLK idle state
Data capture
Data transmission
CS idle state
Data order
Table 2: SPI Standard
SCLK
MA702
CS
GND
SSCK
SSD
TEST
Exposed pad
Mode 0
Mode 3
Low
High
On SCLK rising edge
On SCLK falling edge
High
MSB first
CPOL
CPHA
Data Order (DORD)
Mode 0
Mode 3
0
1
0
1
0 (MSB first)
PWM
Figure 6: Connection for Supply Decoupling
MA702 Rev. 1.1
2/6/2020
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
tcsL
CS
tsclk
tsclkL tsclkH
tcsH
tMISO
tMISO
tidleAngle
tidleReg
tnvm
SCLK
tMISO
MISO
hi-Z
MOSI
MSB
X
LSB
MSB
hi-Z
MSB
X
LSB
MSB
tMOSI
Figure 7: SPI Timing Diagram
tidleAngle
tidleAngle
tidleAngle
tidleReg
tidleReg
tidleAngle
tnvm
tidleReg
CS
MISO
Angle
Angle
Angle
Angle
Reg Value
Angle
Angle
Reg Value
Angle
MOSI
0
0
0
Read Reg Cmd
0
0
Write Reg Cmd
0
0
Figure 8: Minimum Idle Time
Table 3: SPI Timing
Parameter
(6)
Description
Min
Max
tidleAngle
Idle time between two subsequent angle transmissions
150
ns
tidleReg
Idle time before and after a register readout
750
ns
tnvm
Idle time between a write command and a register readout
(delay necessary for non-volatile memory update)
20
ms
tcsL
Time between CS falling edge and SCLK falling edge
80
ns
tsclk
SCLK period
40
ns
tsclkL
Low level of SCLK signal
20
ns
tsclkH
High level of SCLK signal
20
ns
tcsH
Time between SCLK rising edge and CS rising edge
25
ns
tMISO
SCLK setting edge to data output valid
tMOSI
Data input valid to SCLK reading edge
15
15
Unit
ns
ns
NOTE:
6) All values are guaranteed by design.
MA702 Rev. 1.1
2/6/2020
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
SPI Communication
The sensor supports three types of SPI
operation:
Read angle
Read configuration register
Write configuration register
Angle reading can be therefore optimized,
without any loss of information, by reducing the
number of clock counts. In the case of a 12-bit
data output length, only 12 clock counts are
required to get the full sensor resolution.
MSB
Each operation has a specific frame structure
described below.
SPI Read Angle
Every 1µs, new data is transferred into the output
buffer. The master device triggers the reading by
pulling CS low.
When a trigger event is detected, the data
remains in the output buffer until the CS signal is
de-asserted (see Table 4).
LSB
MISO
Angle(15:4)
MOSI
0
If less resolution is needed, the angle can be
read by sending even fewer clock counts (since
the MSB is first).
In case of fast reading, the MagAlpha continues
sending the same data until the data is
refreshed. See the refresh rate section in the
General Characteristics table on page 5.
Table 4: Sensor Data Timing
Event
CS falling edge
CS rising edge
Action
Start reading and freeze
output buffer
Release of the output buffer
See Figure 9 for a diagram of a full SPI angle
reading. See Figure 10 for a partial SPI angle
reading. A full angle reading requires 16 clock
pulses. The sensor MISO line returns:
MSB
LSB
MISO
Angle(15:0)
MOSI
0
The MagAlpha family has sensors with different
features and levels of resolution. See the data
output length section in the General
Characteristics table on page 5 for the number
of useful bits delivered at the serial output. If the
data length is smaller than 16, the rest of the bits
sent are zeros. For example, a data output
length of 12 bits means that the serial output
delivers a 12-bit angle value with four bits of
zeros padded at the end (MISO state remains
zero). If the master sends 16 clock counts, the
MagApha replies with:
MSB
MISO
MOSI
MA702 Rev. 1.1
2/6/2020
LSB
Angle(15:4)
Figure 9: Diagram of a Full 16-Bit SPI Angle
Reading
Figure 10: Diagram of a Partial 8-Bit SPI Angle
Reading
0 0 0 0
0
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
SPI Read Register
A read register operation is constituted of two 16bit frames. The first frame sends a read request,
which contains the 3-bit read command (010)
followed by the 5-bit register address. The last 8
bits of the frame must be all set to 0. The second
frame returns the 8-bit register value (MSB byte).
See Figure 11 for a complete transmission
overview.
First 16-bit SPI frame (read request):
MISO
MSB
MISO
MSB
LSB
Angle(15:0)
LSB
command
MOSI 0 1 0
Angle(15:0)
command
reg. address
MOSI 0 1 0 A4 A3 A2 A1 A0
0 0 0 0 0 0 0 0
reg. value
MISO V7 V6 V5 V4 V3 V2 V1 V0
0 0 0 0 0 0 0 0
MSB
LSB
0
reg. address
1 1 0 1 1
0 0 0 0 0 0 0 0
In the second frame, the MagAlpha replies:
reg. value
MISO MGH MGL X X X X X X
Second 16-bit SPI frame (response):
MOSI
For example, to get the value of the magnetic
level high and low flags (MGH and MGL), read
register 27 (bit 6, bit 7) by sending the following
first frame:
0 0 0 0 0 0 0 0
MSB
MOSI
LSB
0
See Figure 12 for a complete example overview.
Figure 11: Two 16-Bit Frames Read Register Operation
Figure 12: Example Read Magnetic Level Flags High and Low (MGH, MGH) on Register 27, Bit 7-6
MA702 Rev. 1.1
2/6/2020
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
SPI Write Register
Table 7 shows the programmable 8-bit registers.
Data written to these registers are stored in the
on-chip non-volatile memory and reloaded at
power-on automatically. The factory default
register values are shown in Table 8.
A write register operation is constituted of two
16-bit frames. The first frame sends a write
request, which contains the 3-bit write command
(100) followed by the 5-bit register address and
the 8-bit value (MSB first). The second frame
returns the newly written register value
(acknowledge).
The on-chip memory is guaranteed to endure
1,000 write cycles at 25°C.
It is critical to wait 20ms between the first and the
second frame. This is the time taken to write the
non-volatile memory. Failure to implement this
wait period results in the register’s previous
value being read. Note that this delay is only
required after a write request. A read register
request and read angle do not require this wait
time.
The second 16-bit SPI frame (response) is:
reg. value
MISO V7 V6 V5 V4 V3 V2 V1 V0
MSB
LSB
MOSI
0
The read-back register content can be used to
verify the register programming. See Figure 13
for a complete transmission overview.
For example, to set the value of the output
rotation direction (RD) to counterclockwise
(high). Write register 9 by sending the following
first frame:
MSB
MISO
MOSI
LSB
Angle(15:0)
command
1 0 0
reg. address
0 1 0 0 1
reg. value
1 0 0 0 0 0 0 0
Send the second frame after a 20ms wait time. If
the register is written correctly, the reply is:
reg. value
MISO 1 0 0 0 0 0 0 0
The first 16-bit SPI frame (write request) is:
MSB
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
MSB
LSB
MISO
Angle(15:0)
MOSI
command
reg. address
reg. value
1 0 0 A4 A3 A2 A1 A0 V7 V6 V5 V4 V3 V2 V1 V0
MOSI
LSB
0
See Figure 14 for a complete example.
Figure 13: Overview of Two 16-Bit Frames Write Register Operation
MA702 Rev. 1.1
2/6/2020
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
Figure 14: Example Write Output Rotation Direction (RD) to Counterclockwise (High), on Register 9, Bit 7
SSI
SSI is a 2-wire synchronous serial interface for
data reading only. The sensor operates as a
slave to the external SSI master and supports
only angle reading. It is not possible to read or
write registers by SSI.
SSI Communication
Unlike SPI, the sensor SSI only supports angle
reading operation. It is not possible to read or
write registers using SSI. SSI timing
communication is shown in Figure 15 and Table
5.
Figure 15: SSI Timing
Table 5: SSI Timing
Parameter
Description
Min
tssd
Max
Unit
15
ns
tssck
SSCK period
0.04
16
µs
tssckL
Low level of SSCK signal
0.02
8
µs
tssckH
High level of SSCK signal
0.02
8
µs
tm
Transfer timeout (monoflop time)
25
µs
tp
Dead time: SSCK high time for next data reading
40
µs
SSI Read Angle
The bit order of the transmitted data is MSB first
and LSB last. Every 1µs, new data is transferred
into the output buffer. The master device triggers
the reading by driving SSCK high. A full reading
requires up to 17 clock counts (see Figure 16).
MA702 Rev. 1.1
2/6/2020
The first clock is a dummy clock to start the
transmission. The data length is up to 16 bits
long. See the data output length section in the
General Characteristics table on page 5 for the
number of useful bits delivered at the serial
output.
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
The first data MSB is transmitted on the second
clock count. If the data length is less than 16, the
16-bit output word is completed by zeros.
Therefore, the reading can also be performed
with fewer than 16 clock counts. For example, for
a part with a 12-bit data length, it is only
necessary to send the first dummy clock to start
the transmission + 12 clocks to read the angle
data.
When a trigger event is detected, the data
remains in the output buffer until the clock falling
edge for the LSB bit 0 and the transfer timeout
time has passed (see Table 6).
Table 6: Sensor Data Timing
Trigger Event
Release of the Output Buffer
First SSCK pulse rising
edge
SSCK falling edge + time out tm (Fig 15)
Figure 16: Diagram of a Full 16-Bit SSI Angle Reading (with First Dummy Clock)
For consecutive angle readings, see the timing in Figure 17.
Figure 17: Diagram of Two Consecutive 16-Bit SSI Angle Reading with the Required Dead Time between
the Frames
MA702 Rev. 1.1
2/6/2020
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
REGISTER MAP
Table 7: Register Map
Bit 7
MSB
Bit 6
Bit 1
Bit 0
LSB
-
ETY
ETX
-
-
-
-
-
-
-
MG1L
MG2L
-
-
Hex
Bin
0
0x0
00000
Z(7:0)
1
0x1
00001
Z(15:8)
2
0x2
00010
BCT(7:0)
3
0x3
00011
4
0x4
00100
5
0x5
00101
6
0x6
00110
9
0x9
01001
RD
-
-
-
-
27
0x1B
11011
MGH
MGL
-
-
-
-
Bit 5
Bit 2
No
-
Bit 4
-
PPT(1:0)
-
Bit 3
ILIP(3:0)
-
PPT(7:2)
MGLT(2:0)
MGHT(2:0)
Table 8: Factory Default Values
No
Hex
Bin
Bit 7
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LSB
0
0x0
00000
0
0
0
0
0
0
0
0
1
0x1
00001
0
0
0
0
0
0
0
0
2
0x2
00010
0
0
0
0
0
0
0
0
3
0x3
00011
0
0
0
0
0
0
0
0
4
0x4
00100
1
1
0
0
0
0
0
0
5
0x5
00101
0
0
1
1
1
1
1
1
6
0x6
00110
0
0
0
1
1
1
0
0
9
0x9
01001
0
0
0
0
0
0
0
0
Table 9: Programming Parameters
Parameters
Symbol
Number of
Bits
Zero Setting
Bias Current
Trimming
Z
16
BCT
8
Enable Trimming X
ETX
1
Enable Trimming Y
ETY
1
Pulses Per Turn
PPT
8
ILIP
Index Length /
Index Position
Magnetic Field
High Threshold
Magnetic Field
Low Threshold
Rotation Direction
MA702 Rev. 1.1
2/6/2020
Description
See Table
Set the zero position
For side-shaft configuration: reduce the
bias current of the X or Y Hall device
Biased current trimmed in the X direction
Hall device
Biased current trimmed in the Y direction
Hall device
Number of pulses per turn of the ABZ
output
10
4
Parametrization of the ABZ index pulse
Fig 26
MGHT
3
Sets the field strength high threshold
16
MGLT
3
Sets the field strength low threshold
16
RD
1
Determines the sensor positive direction
12
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14
14
18
18
MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
REGISTER SETTINGS
Zero Setting
The zero position of the MagAlpha (a0) can be
programmed with 16 bits of resolution. The angle
streamed out by the MagAlpha (aOUT) is given by
Equation (2):
aOUT = aRAW - a0
(2)
Where aRAW is the raw angle provided by the
MagAlpha front end.
The parameter Z(15:0), which is zero by default,
is the complementary angle of the zero setting.
In decimals, it can be written as shown in
Equation (3):
16
a0 = 2
- Z(15:0)
(3)
Table 10 shows the zero setting parameter.
0
1
2
…
65534
65535
Zero pos.
a0 (16 bit dec)
65536
65535
65534
…
2
1
Zero pos.
a0 (deg)
360.000
359.995
359.989
…
0.011
0.005
20 deg 16
2 61895
360 deg
RD
0
1
Positive Direction
Clockwise (CW)
Counterclockwise (CCW)
k = BRAD / BTAN
Example
To set the zero position to 20 degrees, the
Z(15:0) parameter must be equal to the
complementary angle and can be calculated with
Equation (4):
Z (15 : 0) 216
Table 12: Rotation Direction Parameter
BCT Settings (Bias Current Trimming)
Side Shaft
When the MA702 is mounted on the side of the
magnet, the relation between the field angle and
the mechanical angle is no longer directly linear.
This effect is related to the fact that the tangential
magnetic field is usually smaller than the radial
field. Define the field ratio k with Equation (5):
Table 10: Zero Setting Parameter
Z(15:0)
Figure 8: Positive Rotation Direction of the
Magnetic Field
(5)
Where BRAD and BTAN are the maximum radial
and tangential magnetic fields (see Figure 19).
(4)
In binary, it is written as 1111 0001 1100 0111.
Table 11 shows the content of the registers 0
and 1.
Table 11: Register 0 and 1 Content
Reg Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
0
1
1
0
0
0
1
1
1
1
1
1
1
1
0
0
0
1
Rotation Direction
By default, when looking at the top of the
package, the angle increases when the magnetic
field rotates clockwise (CW) (see Figure 18 and
Table 12).
MA702 Rev. 1.1
2/6/2020
Figure 19: Side-Shaft Field
The ratio k depends on the magnet geometry
and the distance to the sensor. Having a k ratio
different than 1 results in the sensor output
response not being linear with respect to the
mechanical angle. Note that the error curve has
the shape of a double sinewave (see Figure 21).
E is the amplitude of this error.
The X-axis or the Y-axis bias current can be
reduced by programming in order to recover an
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
Table 13: Example of BCT Settings
equal Hall signal for all angles and therefore
suppress the error. The parameter ETX and ETY
controls the direction in which sensitivity is
reduced. The current reduction is set by the
parameter bias current trimming BCT(7:0), which
is an integer from 0 to 255.
E (deg)
0
11.5
19.5
25.4
30.0
33.7
36.9
39.5
41.8
In side-shaft configuration (i.e. the sensor center
is located beyond the magnet outer diameter), k
is greater than 1. For optimum compensation,
the sensitivity of the radial axis should be
reduced by setting the BCT parameter as shown
in Equation (6):
1
BCT (7 : 0) 2581
k
(6)
The graph in Figure 20 shows the optimum BCT
value for a particular k ratio.
200
BCT
150
Magnet Ratio k
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
BCT(7:0)
0
86
129
155
172
184
194
201
207
Determining k with the MagAlpha
It is possible to deduce the k ratio from the error
curve obtained with the default BCT setting (BCT
= 0). For this purpose, rotate the magnet over
one revolution and record the MagAlpha output.
Then plot the error curve (the MagAlpha output
minus the real mechanical position vs the real
mechanical
position)
and
extract
two
parameters: the maximum error E and the
position of this maximum with respect to a zero
crossing am (see Figure 21). k can be calculated
with Equation (7):
100
k
tan(E a m )
tan(a m )
(7)
50
40
0
1
1.5
2
2.5
3
3.5
4
4.5
5
20
k
2E
Error (deg)
m
Figure 20: Relation between the k Ratio and the
Optimum BCT to Recover Linearity
0
Table 13 shows some typical BCT values.
-20
-40
0
50
100
150
200
250
300
350
rotor angle (deg)
Figure 21: Error Curve in Side-Shaft
Configuration with BCT = 0
Some examples are given in Table 13.
Alternatively, the k parameter can be obtained
from the graph of Figure 22.
MA702 Rev. 1.1
2/6/2020
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
Magnetic Field Thresholds
The magnetic flags (MGL and MGH) indicate
that the magnetic field at the sensor position is
out a range defined by the lower (MGLT) and
upper magnetic field thresholds (MGHT) (see
Figure 24).
5
4.5
4
k
3.5
3
2.5
2
1.5
1
0
5
10
15
20
25
30
35
40
E (deg)
Figure 22: Relation between the Error Measured
with BCT = 0 and the Magnet Ratio k
Sensor Orientation
From the dot marked on the package, it is
possible to know whether the radial field is
aligned with the sensor coordinate X or Y (see
Figure 23).
Figure 24: MGH and MGL Signals as a Function
of the Field Strength
MagHys, the typical hysteresis on the signals
MGH and MGL is 6mT. The MGLT and MGHT
thresholds are coded on three bits and stored in
register 6 (see Table 15).
Table 15: Register 6
Register 6
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
MGLT
MGHT
The 3-bit values of MGLT and MGHT correspond
to the magnetic field (see Table 16).
Figure 23: Package Top View with X and Y Axes
Determine which axis needs to be reduced (see
the qualitative field distribution around a ring in
Figure 19). For instance, with the arrangement
depicted in Figure 23, the field along the sensor
Y direction is tangential and weaker. The X-axis
should be reduced (ETX = 1 and ETY = 0). Note
that if both ETX and ETY are set to 1, the current
bias is reduced in both directions the same way
(i.e. without side-shaft correction) (see Table
14).
Table 14: Trimming Direction Parameters
ETX
0
1
ETY
0
1
MA702 Rev. 1.1
2/6/2020
Enable Trimming of the X-Axis
Disabled
Enabled
Enable Trimming of the Y-Axis
Disabled
Enabled
Table 16: MGLT and MGHT: Binary to mT
Relation
MGLT or
MGHT (8)
000
001
010
011
100
101
110
111
Field threshold in mT
From low to high
magnetic field
26
41
56
70
84
98
112
126
(7)
From high to low
magnetic field
20
35
50
64
78
92
106
120
NOTES:
7) Valid for VDD = 3.3V. If different then field threshold is scaled
by the factor VDD/3.3V.
8) MGLT can have a larger value than MGHT.
The alarm flags MGL and MGH are available to
be read in register 27 (bit 6, bit 7), and their logic
state is also given at the digital output pins 11
and 16.
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
To read the MGL and MGH flags via the SPI,
send the 16-bit read command to get the register
27 value:
command
0 1 0
reg. address
1 1 0 1 1
MGL
First
Reading
value
LSB
0 0 0 0 0 0 0 0
MSB
The MA702 responds with the register 27
content in the next transmission:
MGH MGL
Table 17: MGL Multiple Reading Workaround
Register 27 [7:0]
x
x MG1L MG2L x
x
Known Issue Regarding MGL
Pulses with a duration of about 1.3μs to 1.5μs
appear randomly in the MGL signal. They appear
on both pin and register values (Register 27, bit
6).
These pulses appear around angle values of 44,
138, 224, and 318 degrees (sensor output) or in
an interval of ±1.5 degree around these values.
These pulses have an amplitude of 3.3V (VDD).
The minimum interval between two pulses is
100μs.
Workarounds
1. Invert the MGH signal to replace MGL.
The MGL and MGH magnetic thresholds
only differ by a small hysteresis (see Table
16). An inverted MGH signal can be used to
replace the MGL output in the application.
2. Read the MGL signal level twice.
Using two readings, which must be between
2µs and 100µs apart, allows the user to
distinguish erroneous from real transitions.
Table 17 shows examples of different cases.
3. Read register 27 with the SPI and compute a
corrected MGL value using MG1L and
MG2L.
The corrected MGL signal = NOT (MG1L OR
MG2L). This means that the corrected MGL
must be set to 1 only when both MG1L and
MG2L are equal to 0. See the C
implementation below:
Case 1
0
Case 2
Case 3
1
1
MGL Second
Reading (e.g.
20μs After the
First Reading)
Second reading is
not needed
1
0
True
MGL
Value
0
1
0
ABZ Incremental Encoder Output
The MA702 ABZ output emulates a 10-bit
incremental encoder (such as an optical
encoder) providing logic pulses in quadrature
(see Figure 25). Compared to signal A, signal B
is shifted by a quarter of the pulse period. Over
one revolution, signal A pulses N times, where N
is programmable from 1 to 256 pulses per
revolution. The number of pulses per channel
per revolution is programmed by setting the
parameter PPT, which consists of eight bits split
between registers 0x4 and 0x5 (see Table 7).
The factory default value is 256. Table 18
describes how to program PPT(7:0) to set the
required resolution.
Table 18: PPT
Pulses per
Turn
1
2
3
4
…
253
254
255
256
PPT(7:0)
00000000
00000001
00000010
00000011
…
11111100
11111101
11111110
11111111
Edges per
Turn
4
8
12
16
…
1012
1016
1020
1024
MIN
…
MAX
For example, to set 120 pulses per revolution
(i.e. 480 edges), set PPT to 120 - 1 = 119. In
binary: 01110111. Thus the registers 4 and 5
must be set as shown in Table 19.
Table 19: Example PPT Setting for 120 Pulses
R4
R5
B7
1
0
B6
1
0
B5
0
0
B4
0
1
B3
0
1
B2
0
1
B1
0
0
B0
0
1
correctedMGL = !(MG1L | MG2L)
MA702 Rev. 1.1
2/6/2020
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
ABZ Jitter
The ABZ state is updated at a frequency of
16MHz, enabling accurate operation up to a very
high rpm (above 105 rpm).
The jitter characterizes how far a particular ABZ
edge can occur at an angular position different
from the ideal position (see Figure 28).
Figure 25: Timing of the ABZ Output
Signal Z (zero or index) raises only once per turn
at the zero-angle position.
Figure 28: ABZ Jitter
The position and length of the Z pulse is
programmable via bits ILIP(3:0) in register 0x5
(see Figure 26).
The measurable jitter is composed by a
systematic jitter (i.e. always the same deviation
at a given angle) and a random jitter.
The random jitter reflects the sensor noise.
Therefore, the edge distribution is the same as
the SPI output noise. Like the sensor resolution,
it is defined as the 3σ width of this distribution.
Figure 26: ILIP Parameter Effect on Index Shape
By default, the ILIP parameter is 0000. The index
rising edge is aligned with the channel B falling
edge. The index length is half the A or B pulse
length.
ABZ Hysteresis
A hysteresis larger than the output noise is
introduced on the ABZ output to avoid any
spurious transitions (see Figure 27).
Figure 27: Hysteresis of the Incremental Output
MA702 Rev. 1.1
2/6/2020
In fact, the random jitter is a function of the
rotation speed. At a lower speed, the random
jitter is smaller than the sensor noise.
This is a consequence of the fact that the
probability of measuring an edge at a certain
distance from the ideal position depends on the
number of ABZ updates at this position.
The minimum field for ABZ reading is 30mT.
PWM Absolute Output
This output provides a logic signal with a duty
cycle proportional to the angle of the magnetic
field. The PWM frequency is indicated in the
General Characteristics table on page 5. The
duty cycle is bounded by a minimum value
(1/130 of the period) and a maximum value
(129/130 of the period) (see Figure 29), so the
duty cycle varies from 1/130 to 129/130 with a
resolution of 12 bits. The angle can be retrieved
by measuring the on time. Since the absolute
PWM frequency can vary from chip to chip or
with the temperature, accurate angle detection
requires the measurement of the duty cycle (i.e.
the measurement of both the on time (ton) and
the off time (toff)).
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
The angle can be calculated with Equation (8):
angle(in deg) 360
t ON
1
130
1 (8)
128
t ON t OFF
Figure 29 shows one period of the PWM signal.
The period T is 1 / fPWM, where fPWM is the PWM
frequency
indicated
in
the
General
Characteristics table on page 5.
Top Signal: 0°
Bottom Signal: Full Scale (i.e. 360°(1 – 1 / 4096))
Figure 29: PWM Output Timing
MA702 Rev. 1.1
2/6/2020
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
TYPICAL APPLICATION CIRCUITS
Figure 30: Typical Configurations Using SPI Interface and MGH/MGL Signals
Figure 31: Typical Configuration Using ABZ Interface
MA702 Rev. 1.1
2/6/2020
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MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
PACKAGE INFORMATION
QFN-16 (3mmx3mm)
MA702 Rev. 1.1
2/6/2020
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26
MA702 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS
APPENDIX A: DEFINITIONS
Effective Resolution
(3σ noise level)
This is the smallest angle increment distinguishable from the noise. The
resolution is measured by computing three times σ (the standard
deviation in degrees) taken over 1,000 data points at a constant position.
The resolution in bits is obtained with: log2(360/6σ).
Refresh Rate
Rate at which new data points are stored in the output buffer.
ABZ Update Rate
Rate at which a new ABZ state is computed. The inverse of this rate is
the minimum time between two ABZ edges.
Latency
The time elapsed between the instant when the data is ready to be read
and the instant at which the shaft passes that position. The lag in degrees
is
, where 𝑣 is the angular velocity in deg/s.
Power-Up Time
Time until the sensor delivers valid data starting at power up.
Maximum deviation between the average sensor output (at a fixed
position) and the true mechanical angle.
400
sensor out (deg)
350
300
lag
250
ideal
sensor output
200
150
INL
100
Integral Nonlinearity
(INL)
0
sensor out
best straight fit
resolution
( ± 3 )
50
0
100
200
300
400
500
600
700
rotor position (deg)
Figure A1: Resolution, INL, Lag
INL can be obtained from the error curve
, where
is the average over 1000 sensor output and is the mechanical
angle indicated by a high precision encoder (
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