MA734
8-Bit to 12.5-Bit, 3µs Low-Latency
Contactless Angle Sensor
DESCRIPTION
FEATURES
The MA734 is a MagAlpha digital angle sensor
that 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 measurements from static angle
measurement to high-speed rotation. The digital
filtering is adjustable to optimize control loop
performance when used in servo motor
applications.
This sensor supports a wide range of magnetic
field strengths and spatial configurations. Both
end-of-shaft and side-shaft (off-axis mounting)
configurations are supported.
The MA734 detects the strength of the magnetic
field, and includes configurable thresholds that
can be used for push-button human-machine
interface (HMI) applications or for diagnostic
purposes. An on-chip, non-volatile memory
(NVM) provides storage for configuration
parameters, such as the reference zero-angle
and magnetic field detection thresholds. It is also
possible to program the MA734 with volatile
registers without accessing the NVM.
The MA734 is available
(3mmx3mm) package.
in
a
QFN-16
Programmable 8-Bit to 12.5-Bit Resolution
Absolute Angle Encoder
3µs of Latency at Constant Rotation Speed
SPI Serial Interface for Digital Angle
Readout and Chip Configuration
Programmable Magnetic Field Strength
Detection for Diagnostic Checks
NVM Read/Write Command Extends
Memory Life
3.3V, 11mA Supply Current
-40°C to +125°C Operating Temperature
0rpm to 60,000rpm Rotation
Interrupt Out when Angle Change Is
Detected
Available in a QFN-16 (3mmx3mm)
Package
APPLICATIONS
General-Purpose Angle Measurement
High-Resolution Angle Encoders
Automotive Position Sensing
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”, the MPS logo, and “Simple, Easy Solutions” are
registered trademarks of Monolithic Power Systems, Inc. or its subsidiaries.
TYPICAL APPLICATION
3.3V
1µF
Controller
VDD
MISO
SPI
Interface
Master
MOSI
SCLK
MA734
/CS
Target Magnet
IRQ
GND
MA734 Rev. 1.0
5/27/2021
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1
MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
ORDERING INFORMATION
Part Number*
MA734GQ
Package
QFN-16 (3mmx3mm)
Top Marking
See Below
MSL Rating
1
* For Tape & Reel, add suffix -Z (e.g. MA734GQ-Z).
TOP MARKING
BQFY
LLL
BQF: Product code of MA734GQ
Y: Year code
LLL: Lot number
PACKAGE REFERENCE
TOP VIEW
GND MISO N/C
8
N/C
7
6
/CS
5
9
4
MOSI
3
NVM
TEST
10
MGL
11
2
ERR
SCLK
12
1
IRQ
17
PAD
13
14
15
16
VDD
N/C
N/C
MGH
QFN-16 (3mmx3mm)
MA734 Rev. 1.0
5/27/2021
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2
MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
PIN FUNCTIONS
Pin #
Name
1
IRQ
2
ERR
3
NVM
4
5
6
MOSI
/CS
NC
7
MISO
8
9
10
11
12
13
14
15
GND
NC
TEST
MGL
SCLK
VDD
NC
NC
16
17
Description
Interrupt on angle change. Output. Indicates that the angle change has exceeded the
defined threshold.
Error flag. This pin is an active high output.
Non-volatile memory (NVM). This pin is an output that indicates that the chip is busy
accessing the NVM.
Data in (SPI). This pin is an internal pull-down resistor input.
Chip select (SPI). This pin is an internal, active low, pull-down resistor input.
No connection. This pin is not internally connected.
Data out (SPI). This pin is an output, and is pulled down when /CS is logic 1 (i.e. SPI is
inactive).
Supply ground.
No connection. This pin is not internally connected..
Factory use only. Connect TEST to ground.
Digital output indicating field strength below MGLT level. Output.
Clock (SPI). This pin is an internal pull-down resistor input.
3.3V supply.
No connection. This pin is not internally connected.
No connection. This pin is not internally connected.
Digital output. This pin is an output that indicates the field strength above the MGHT
MGH
level.
Exposed pad Recommended not to solder. Leave this pin floating.
θJA
θJC
ABSOLUTE MAXIMUM RATINGS (1)
Thermal Resistance (3)
Supply voltage .............................-0.5V to +4.6V
Input pin voltage (VI) .......................-0.5V to +6V
Output pin voltage (VO) ................-0.5V to +4.6V
Continuous power dissipation (TA = 25°C) (2)
...................................................................... 2W
Junction temperature ................................150°C
Lead temperature .....................................260°C
Storage temperature ................ -65°C to +150°C
QFN-16 (3mmx3mm) ............. 50 ....... 12 ... °C/W
ESD Ratings
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.
Human body model (HBM) .......................... 2kV
Charged device model (CDM) ..................... 2kV
MA734 Rev. 1.0
5/27/2021
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3
MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
ELECTRICAL CHARACTERISTICS
Parameter
Symbol Condition
Recommended Operating Conditions
Supply voltage
VDD
Supply current
IDD
Ambient (operating)
temperature
Applied magnetic
field
Min
Typ
Max
Units
3.0
3.3
3.6
V
11
12.5
mA
+125
°C
TA -40°C to +125°C
TA
-40
B
30
60
mT
GENERAL CHARACTERISTICS
VDD = 3.3V, 45mT < B < 100mT, TA = -40°C to +125°C, unless otherwise noted.
Parameter
Symbol Condition
Absolute Output – Serial
Effective resolution (±3σ)
(5)
Noise RMS
(5)
Typ
Max
Filter window, τ = 4µs, at 25°C
7.2
8.0
Filter window, τ = 1ms, at 25°C
10.2
11.5
Filter window, τ = 4ms, at 25°C
11.6
12.5
Filter window, τ = 4µs, at 25°C
0.2
0.4
Filter window, τ = 1ms, at 25°C
0.02
0.05
Filter window, τ = 4ms, at 25°C
0.01
0.02
Resolution drift in
temperature (5)
Refresh rate
Data output length
Response Time
-0.003
850
16
Start-up time (4)
Latency (4)
Filter cutoff frequency (4)
Min
fCUTOFF
fCUTOFF
fCUTOFF
Filter window, τ = 4µs
Filter window, τ = 1ms
Filter window, τ = 4ms
Constant speed propagation delay
Filter window, τ = 4µs
Filter window, τ = 1ms
Filter window, τ = 4ms
980
Units
bits
deg
bits/°C
1100
16
kHz
bits
0.6
16
65
3
95
380
95
ms
ms
ms
µs
kHz
Hz
Hz
0.7
deg
1.1
deg
0.01
deg/°C
0.5
0.7
0.01
0.35
deg
deg
deg/mT
deg/V
Accuracy
INL at 25°C
INL between -40°C and
+125°C (5)
Output Drift
Temperature-induced drift
at room temperature (5)
Temperature-induced
variation (5)
Magnetic field induced (5)
Voltage supply induced (5)
MA734 Rev. 1.0
5/27/2021
At room temperature across the full field
range
Across the full temperature range and
field range
From 25°C to 85°C
From 25°C to 125°C
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4
MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
GENERAL CHARACTERISTICS (continued)
VDD = 3.3V, 45mT < B < 100mT, TA = -40°C to +125°C, unless otherwise noted.
Parameter
Symbol Condition
Min
Magnetic Field Detection Thresholds
Accuracy (5)
Hysteresis (5)
MagHys
(5)
Temperature drift
Digital I/O
Input high voltage
Input low voltage
Output low voltage
(5)
Output high voltage
(5)
Pull-up resistor
Pull-down resistor
(4)
Rising edge slew rate
Falling edge slew rate (4)
VIH
VIL
VOL
VOH
RPU
RPD
tR
tF
CL = 50pF
CL = 50pF
Max
5
6
-600
Units
mT
mT
PPM/°C
2.5
3.3
5.5
V
-0.3
0
+0.8
V
0
0.4
V
IOL = 4mA
IOH = 4mA
Typ
2.4
3.3
46
66
97
kΩ
43
55
97
kΩ
0.7
0.7
V
V/ns
V/ns
Notes:
4)
5)
Guaranteed by design.
Guaranteed by characterization testing.
MA734 Rev. 1.0
5/27/2021
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MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
TYPICAL CHARACTERISTICS
VDD = 3.3V, TA = 25°C, unless otherwise noted.
Error Curves
Noise Spectrum at 50mT
with FW = 10
Filter Transfer Function
with FW = 10
Supply Current
MA734 Rev. 1.0
5/27/2021
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MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
FUNCTIONAL BLOCK DIAGRAM
VDD
(3.3V)
MA734
NVM
NVM
MGL
2D HallEffect
Device
Registers
Amplitude
Detection
MGH
ERR
/CS
BP
Serial Interface
φ
Phase
Detection
Digital
Conditioning
Track &
Compare
SCLK
MISO
MOSI
IRQ
GND
Figure 1: Functional Block Diagram
MA734 Rev. 1.0
5/27/2021
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MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
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 MPS’s proprietary
SpinAxisTM method, which directly digitizes the
direction of the field without the need for complex
arctangent computation or feedback loop-based
circuits (interpolators).
SpinAxisTM
The
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 outputted from
the front end to the digital conditioning block.
Start
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 mid-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
plus sign indicates the sensitive point. Both the
rotation direction and the zero angle can be
programmed.
Stop
Figure 2: Phase Detection Method across the
Sine Waveform (Top) and Time-to-Digital
Converter Clock
The output of the front end delivers a digital
number proportional to the angle of the magnetic
field at a rate of 1MHz in a straightforward, openloop 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+ 2τs
(1+ τs)2
(1)
Where τ is the filter time constant (See Table 15
on page 21).
Sensor Magnet Mounting
The MA734’s sensitive area (where the Hall
devices are placed) is confined within a region
less than 100µm wide and has multiple
integrated Hall devices. This volume is located
MA734 Rev. 1.0
5/27/2021
Figure 3: Detection Point and Default Positive
Direction
This type of detection provides flexibility for
angular encoder design. The sensor only
requires the magnetic vector to lie within the
sensor plane with a field amplitude of at least
30mT. The MA734 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 MA734 sensor
on the rotation axis of a permanent magnet (e.g.
a diametrically magnetized cylinder) (see Figure
4 on page 9). The recommended magnet is a
Neodymium alloy (N35) cylinder with dimensions
of Ø5x3mm, inserted into an aluminum shaft with
a 1.5mm air gap between the magnet and the
sensor (surface of package). For good linearity,
position the sensor with a precision of 10% of the
magnet’s radius.
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8
MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
Serial Interface
The sensor supports the serial peripheral
interface (SPI) standard for angle reading and
register programming.
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 not
directly proportional to the mechanical angle.
The MA734 can be adjusted to compensate for
this effect and recover the linear relationship
between the mechanical angle and the sensor
output. With multiple pole pair magnets, the
MA734 indicates multiple rotations for each
mechanical turn.
SPI
The SPI is a four-wire, synchronous, serial
communication interface. The MA734 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 does not
require additional action. There is no minimum
clock rate. Real-world data rates depend on the
PCB layout quality and signal trace length. See
Figure 8, Figure 9, and Table 3 on page 11 for
SPI timing.
Table 1: SPI Specification
SCLK Idle State
Data Capture
Data Transmission
/CS Idle State
Data Order
Mode 0
Mode 3
Low
High
On SCLK rising edge
On SCLK falling edge
High
MSB first
Table 2: SPI Standard
CPOL
CPHA
Data Order (DORD)
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 lowimpedance path to GND (see Figure 6).
3.3V
VDD
1µF
MA734
GND
TEST
Exposed
Pad
Figure 6: Supply Decoupling Connection
In general, the MA734 works well with or without
the exposed pad connected. It is recommended
that the exposed pad be left floating.
MA734 Rev. 1.0
5/27/2021
Mode 0
Mode 3
0
1
0
1
0 (MSB first)
All commands to the MA734 (whether for writing
or reading register content) must be transferred
through the SPI MOSI pin and must be 16 bits
long. See the SPI Communication section on
page 12 for details.
SPI Signal Routing on a PCB
For a reliable data transfer through the SPI bus
between the sensor (slave) and the controller
(master), take extra care with the PCB design,
especially the SCLK line. The steps below are
recommended:
Properly shield all SPI signals with a GND
plane on both sides of each trace, as well as
a GND plane underneath the SPI traces.
Place vias along these traces to connect the
top and bottom GND planes.
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MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
To avoid EMI issues, route the SCLK signal
away from the other SPI signals and noise
sources. The distance should be at least 3
times the SCLK trace width.
Insert an RC low-pass filter on SCLK. This
RC filter must be located close to the sensor;
it is recommended to use a 200Ω serial
resistor with a 10pF shunt capacitor in order
to have a filter with a cutoff frequency of
about 80MHz (see Figure 7).
Use a star topology for the GND connection,
and keep it as direct and short as possible to
avoid ground loops.
Insert RC low-pass filters on MISO and MOSI
signals. The RC filter on MOSI must be
located close to the controller, and the filter
on MISO must be located close to the
sensor. It is recommended to use a 200Ω
resistor with a 10pF capacitor.
Avoid significant trace length mismatch
between the SPI signals, especially between
the MISO, MOSI, and SCLK signals. Design
the PCB such that the trace lengths are equal
for similar propagation delay.
If possible, avoid vias on the SCLK signal.
Host/Master
Processor
MA734
/CS
SCLK
200
10pF
200
MOSI
SPI
Interface
Master
10pF
200
MISO
10pF
Figure 7: Example of RC Low-Pass Filter on SPI Signals
MA734 Rev. 1.0
5/27/2021
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10
MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
tIDLE_ANGLE
tIDLE_READ_REG
tIDLE_WRITE_REG
tSTORE_REG_TO_NVM
tCSL
/CS
SCLK
tSCLK
tSCLKLtSCLKH
tMISO
MISO
tMISO
Hi-Z
tMISO
MSB
tMOSI
MOSI
tSTORE_ALL_REG_TO_NVM
tRESTORE_ALL_REG_FROM_NVM
tCLEAR_FAULT
tCSH
X
LSB
Hi-Z
MSB
X
MSB
tMOSI
MSB
LSB
Figure 8: SPI Timing Diagram (Mode 3)
tIDLE_ANGLE tIDLE_ANGLE tIDLE_ANGLE tIDLE_READ_REG tIDLE_READ_REGtIDLE_ANGLE tIDLE_WRITE_REG tIDLE_WRITE_REG
/CS
MISO
Angle
Angle
Angle
Angle
Reg Value
Angle
Angle
Reg Value
Angle
MOSI
0
0
0
Read Reg.
Command
0
0
Write Reg.
Command
0
0
Figure 9: Minimum Idle Time
Table 3: SPI Timing
Parameter
(6)
Description
Min
Max
Unit
Idle time between two subsequent angle transmissions
120
-
ns
tIDLE_READ_REG
Idle time before and after a register readout
120
-
ns
tIDLE_WRITE_REG
Idle time before and after a register write
120
-
ns
Time required to store a single register to the NVM
23
-
ms
Time required to store all registers to the NVM
704
-
ms
Time required to restore all registers from the NVM
240
-
µs
Time required to clear the error flags (register 26)
40
-
ns
tCSL
Time between /CS falling edge and SCLK falling edge
120
-
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
20
-
ns
tMISO
SCLK falling edge to data output valid
-
15
ns
tMOSI
Data input valid to SCLK reading edge
15
-
ns
tIDLE_ANGLE
tSTORE_REG_TO_NVM
tSTORE_ALL_REG_TO_NVM
tRESTORE_ALL_REG_FROM_
NVM
tCLEAR_FAULT
Note:
6) Guaranteed by design.
MA734 Rev. 1.0
5/27/2021
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11
MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
SPI Communication
The MA734 supports the following types of SPI
operation:
11
10
9
8
7
6
5
4
3
2
1
13
12
11
10
9
8
7
6
5
4
3
2
1
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
15
14
13
12
11
10
9
8
10
9
8
Angle
14
13
12
11
0x00
SPI Read Register
A read register operation consists of two 16-bit
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 all be set to 0. The second
frame returns the 8-bit register value (MSB byte)
with an 8-bit angle value.
MSB
LSB
MISO
0
MOSI
Angle[15:0]
Command Reg. Address
0 1 0 A4 A3 A2 A1 A0
0
0
0 0 0 0 0 0 0 0
Second 16-bit SPI frame (response):
Reg. Value
Angle[15:8]
V7 V6 V5 V4 V3 V2 V1 V0
MSB
Angle
MOSI
8
First 16-bit SPI frame (read request):
SCLK
14
9
Figure 11: Partial 8-Bit SPI Angle Reading
Diagram
MISO
15
10
/CS
/CS
MISO
11
15
Figure 10 shows a diagram of a full SPI angle
reading. Figure 11 shows a partial SPI angle
reading.
12
12
MOSI
Table 4: Sensor Data Timing
Event
Action
Start reading and freeze
/CS falling edge
output buffer
/CS rising edge
Release the output buffer
13
13
MISO
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).
14
14
SCLK
Read angle
Read register
Write register
Store a single register value to the NVM
Store all register values to the NVM
Restore all register values from the NVM
Clear error flags
15
15
LSB
MOSI
0
0x0000
Figure 10: Full 16-Bit SPI Angle Reading Diagram
A full angle reading requires 16 clock pulses.
The sensor MISO line returns:
MSB
LSB
MISO
Angle[15:0]
MOSI
0
If less resolution is sufficient, the angle can be
read by sending fewer clock counts, since the
MSB is first (see Figure 11). If the reading cycle
is shorter than the refresh time, the MA734
continues sending the same data until the data
refreshes (for the refresh rate, see the General
Characteristics section on page 4).
Figure 12 on page 13 shows a complete
transmission.
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:
MSB
LSB
MISO
MOSI
Angle[15:0]
Command
0 1 0
Reg. Address
1 1 0 1 1
0 0 0 0 0 0 0 0
In the second frame, the MA734 replies:
Reg. Value
Angle[15:8]
MISO
MGH MGL X X X X X X
MSB
MOSI
MA734 Rev. 1.0
5/27/2021
LSB
0
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MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
tIDLE_READ_REG
15
14
13
12
11
10
9
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
13
8
7
6
5
4
3
2
1
0
7
6
5
12
11
10
9
8
7
6
4
3
2
1
0
7
6
5
4
3
2
1
0
5
4
3
2
1
0
1
0
/CS
SCLK
MISO
Angle
0
MOSI
1
0
4
3
2
1
0
7
Angle
6
5
Register Address
4
3
2
1
0
15
14
13
12
11
Register Value
10
9
0x00
8
7
6
5
4
3
2
0x0000
Read Command
Figure 12: Read Register Operation with Two 16-Bit Frames
SPI Write Register
A write register operation consists 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 8bit value (MSB first). The second frame returns
the newly written register value (acknowledge)
with an 8-bit angle value.
The readback register content can be used to
verify the register programming. Figure 13
shows a complete transmission overview.
The first 16-bit SPI frame (write request) is:
MISO
MSB
For example, to set the value of the output
rotation direction (RD) to counterclockwise (RD
bit = 1), write register 9 by sending the following
first frame:
MSB
LSB
Angle[15:0]
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
Command
1 0 0
MOSI
Reg. Value
Angle[15:8]
MISO
Reg. Value
Angle[15:8]
V7 V6 V5 V4 V3 V2 V1 V0
MSB
1 0 0 0 0 0 0 0
MSB
LSB
MOSI
LSB
MOSI
Reg. Value
1 0 0 0 0 0 0 0
Then send the second frame. If the register is
written correctly, the reply is:
The second 16-bit SPI frame (response) is:
MISO
Reg. Address
0 1 0 0 1
0
0
tIDLE_WRITE_REG
15
14
13
12
11
10
9
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
13
8
7
6
5
4
3
2
1
0
7
6
5
12
11
10
9
8
7
6
4
3
2
1
0
7
6
5
4
3
2
1
0
5
4
3
2
1
0
1
0
/CS
SCLK
MISO
MOSI
Angle
1
0
0
4
3
2
1
Register Address
0
7
Angle
6
5
4
3
2
1
Register Value to Write
0
15
14
13
12
11
Register Value
10
9
8
7
6
5
4
3
2
0x0000
Write Command
Figure 13: Write Register Operation with Two 16-Bit Frames
MA734 Rev. 1.0
5/27/2021
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13
MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
commands, and then the store commands can
save one or all registers to the NVM.
Non-Volatile Memory (NVM) Operation
The MA734 contains a non-volatile memory
(NVM) to store the chip configuration during
shutdown. The values stored in the NVM are
automatically loaded to the sensor’s registers at
start-up. It is possible to manually force restoring
the NVM values to the registers using the
Restore All Registers from the NVM SPI
command.
Commands are ignored if the NVM is busy
executing a previously received command. To
check that the NVM is available and ready to
receive a new command, observe the NVM pin
level:
The registers can be copied to the NVM using
either of two SPI commands:
High: Busy
Low: Available to receive new commands
SPI Store a Single Register to the NVM
The current value of a specific register can be
stored in the NVM. Commands are ignored if the
NVM is busy executing a previously received
command (see Figure 14).
1. Store a Single Register to the NVM
2. Store All Registers to the NVM
The desired configuration must first be written to
the registers through the write register
tSTORE_REG_TO_NVM
15
14
13
12
11
10
9
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
8
7
6
5
4
3
2
1
0
6
5
4
3
2
1
0
/CS
SCLK
MISO
MOSI
Angle
1
1
1
4
3
2
1
0
7
Angle
6
5
Register Address
4
3
2
1
0
15
14
13
12
11
10
9
0x00
8
7
0x0000
Store Reg. to the NVM Command
Figure 14: Store a Single Register to the NVM Operation with Two 16-Bit Frames
Commands are ignored if the NVM is busy
executing a previously received command.
SPI Store All Registers to the NVM
The user can store the current value of all
registers in the NVM (see Figure 15).
tSTORE_ALL_REG_TO_NVM
15
14
13
12
11
10
9
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
8
7
6
5
4
3
2
1
0
6
5
4
3
2
1
0
/CS
SCLK
MISO
MOSI
Angle
1
1
0
12
11
10
9
8
7
Angle
6
5
4
3
2
1
0x000
0
15
14
13
12
11
10
9
8
7
0x0000
Store All Reg. to the NVM Command
Figure 15: Store All Registers to the NVM Operation with Two 16-Bit Frames
SPI Restore All Registers from the NVM
The user can also restore the value of all
registers from the NVM. This operation is done
MA734 Rev. 1.0
5/27/2021
automatically during each start-up (see Figure
16). Commands are ignored if the NVM is busy
executing a previously received command.
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MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
tRESTORE_ALL_REG_FROM_NVM
15
14
13
12
11
10
9
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
8
7
6
5
4
3
2
1
0
6
5
4
3
2
1
0
/CS
SCLK
MISO
MOSI
Angle
1
0
12
1
11
10
9
8
Angle
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
0x000
8
7
0x0000
Restore All Reg. from the NVM Command
Figure 16: Restore All Registers from the NVM Operation with Two 16-Bit Frames
SPI Clear Error Flags
The error flags on the ERR pin and in register 26
can be cleared using the SPI Clear Error Flags
command (see Figure 17).
tCLEAR_FAULT
15
14
13
12
11
10
9
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
8
7
6
5
4
3
2
1
0
6
5
4
3
2
1
0
/CS
SCLK
MISO
MOSI
Angle
0
0
1
12
11
10
9
8
7
Angle
6
5
4
3
2
1
0
15
14
13
12
11
10
9
0x000
8
7
0x0000
Clear Fault Command
Figure 17: Clear Error Flags Operation with Two 16-Bit Frames
Table 5 shows a summary of all SPI commands.
Table 5: SPI Command List Overview
Command
Bits[15:13]
Register
Address
Required?
Register
Value
Required?
Returned Value
Read Angle
000
No
No
16-bit angle
Read Register
010
Yes
No
8-bit angle + register value
Write Register
100
Yes
Yes
8-bit angle + register value
Store Single Register to the NVM
111
Yes
No
16-bit angle
Store All Registers to the NVM
110
No
No
16-bit angle
Restore All Registers from the NVM
101
No
No
16-bit angle
Clear Error Flags
001
No
No
16-bit angle
Command Name
MA734 Rev. 1.0
5/27/2021
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15
MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
REGISTER MAP
Table 6: Register Map
# of
Registers
Hex
Binary
R/W
Bit[7]
(MSB)
0
0x0
00000
R/W
1
0x1
00001
R/W
Z[15:8]
2
0x2
00010
R/W
BCT[7:0]
3
0x3
00011
R/W
6
0x6
00110
R/W
7
0x7
00111
R/W
8
0x8
01000
R/W
9
0x9
01001
R/W
10
0xA
01010
R/W
14
0xE
01110
R/W
26
0x1A
11010
R
-
-
-
27
0x1B
11011
R
MGH
MGL
-
Bit[6]
Bit[3]
Bit[2]
Bit[1]
Bit[0]
(LSB)
-
-
-
ETY
ETX
MGHT[2:0]
-
-
-
MG
-
-
-
-
-
-
-
-
-
ERRPAR
ERRMEM
ERRNVM
-
-
-
-
-
-
Bit[5]
Bit[4]
Z[7:0]
-
-
-
MGLT[2:0]
IRQM
RAR
HYST[5:0]
THR[7:0]
RD
-
-
REF[7:0]
FW[3:0]
Table 7: Factory Default Values
# of
Registers
Hex
Binary
R/W
Bit[7]
(MSB)
Bit[6]
Bit[5]
Bit[4]
Bit[3]
Bit[2]
Bit[1]
Bit[0]
(LSB)
0
0x0
00000
R/W
0
0
0
0
0
0
0
0
1
0x1
00001
R/W
0
0
0
0
0
0
0
0
2
0x2
00010
R/W
0
0
0
0
0
0
0
0
3
0x3
00011
R/W
0
0
0
0
0
0
0
0
6
0x6
00110
R/W
0
0
0
1
1
1
0
1
7
0x7
00111
R/W
1
0
0
0
0
0
1
1
8
0x8
01000
R/W
0
1
0
0
0
0
0
0
9
0x9
01001
R/W
0
0
0
0
0
0
0
0
10
0xA
01010
R/W
0
1
0
0
0
0
0
0
14
0xE
01110
R/W
1
0
1
0
0
0
0
0
MA734 Rev. 1.0
5/27/2021
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16
MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
Table 8: Programming Parameters
Parameters
Zero setting
Bias current
trimming
Enable trimming X
Enable trimming Y
Enable magnetic
field threshold
Magnetic field
high threshold
Magnetic field low
threshold
IRQ mode
Reference autorefresh
Hysteresis
Threshold
Rotation direction
Reference
Filter window
MA734 Rev. 1.0
5/27/2021
Symbol
Z
# of Bits
16
BCT
8
ETX
ETY
1
1
Description
Sets the zero position
For side-shaft configuration: reduces 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
MG
1
Activates magnetic field threshold detection
MGHT
3
Sets the field strength high threshold
14
MGLT
3
Sets the field strength low threshold
14
IRQM
1
19
RAR
1
HYST
THR
RD
REF
FW
6
8
1
8
4
IRQ pin in logic or latched mode
IRQ pin: automatically updates the reference at each
detection change
Hysteresis of the IRQ signal in logic mode
IRQ signal detection threshold
Determines the sensor positive direction
IRQ pin: reference position
Size of the digital filter window
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See Table
9
11
12
12
-
18
20
16
10
17
15
17
MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
REGISTER SETTINGS
Zero Setting
The MA734’s zero position (a0) can be
programmed with 16 bits of resolution. The angle
streamed out by the MA734 (aOUT) is calculated
with Equation (2):
aOUT = aRAW - a0
(2)
Where aRAW is the raw angle provided by the
MA734’s front end.
linear. This effect is related to the fact that the
tangential magnetic field is usually smaller than
the radial field. Calculate the field ratio (k) with
Equation (3):
k = BRAD /BTAN
Where BRAD and BTAN are the maximum radial
and tangential magnetic fields (see Figure 19).
BRAD
The parameter Z[15:0], is the zero-angle position
coded on 16 bit (see Table 9).
Table 9: Zero-Setting Parameter
Zero Position
Z[15:0]
a0 (deg)
0
0
1
0.005
2
0.011
…
…
65534
359.989
65535
359.995
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 10).
(3)
BTAN
BTAN
BRAD
Figure 19: Side-Shaft Field
The k ratio depends on the magnet geometry
and the distance to the sensor. Having a k ratio
other 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
on page 19). E is the amplitude of this error.
The X-axis or the Y-axis bias currents can be
reduced to recover an equal Hall signal for all
angles, and therefore suppress the error. The
ETX and ETY parameters control the direction in
which sensitivity is reduced. The current
reduction is set by the parameter bias current
trimming register, BCT[7:0], which is an integer
from 0 to 255.
Figure 18: Positive Rotation Direction of the
Magnetic Field
Table 10: Rotation Direction Parameter
RD
Positive Direction
0
Clockwise (CW)
1
Counterclockwise (CCW)
BCT Settings (Bias Current Trimming)
Side-Shaft
When the MA734 is mounted on the side of the
magnet, the relationship between the field angle
and the mechanical angle is no longer directly
MA734 Rev. 1.0
5/27/2021
In side-shaft configuration (i.e. the sensor center
is located beyond the magnet outer diameter), k
> 1. If k is known, set BCT using Equation (4):
1
BCT[7 : 0] = 258 1
k
(4)
Figure 20 on page 19 shows the optimum BCT
value for a particular k ratio.
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18
40
150
20
Error (deg)
200
Error (deg)
BCT
MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
100
aMm
2E
2E
0
-20
50
-40
0
1
1.5
2
2.5
3
3.5
4
4.5
5
0
k
150
200
250
300
350
Rotor Angle (deg)
Figure 21: Error Curve in Side-Shaft
Configuration with BCT = 0
Table 11 shows some typical BCT values.
Table 11 shows some examples. Alternatively,
the k parameter can be obtained using Figure
22.
Table 11: Example of BCT Settings
E (deg)
Magnet Ratio k
BCT[7:0]
0
1.0
0
11.5
1.5
86
19.5
2.0
129
25.4
2.5
155
30.0
3.0
172
33.7
3.5
184
36.9
4.0
194
39.5
4.5
201
41.8
5.0
207
5
4.5
4
k
3.5
3
2.5
Determining k
The k ratio can be deduced from the error curve
obtained with the default BCT setting (BCT = 0).
Rotate the magnet more than one revolution and
record the device’s output. Next, plot the error
curve (the 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 (5):
tan(E + aM )
tan(aM )
100
rotor angle (deg)
Figure 20: Relationship between the k Ratio and
the Optimum BCT to Recover Linearity
k=
50
(5)
2
1.5
1
0
5
10
15
20
25
30
35
40
E (deg)
Figure 22: Relationship between the Error
Measured with BCT = 0 and the Magnet Ratio k
Sensor Orientation
The dot marked on the package indicates
whether the radial field is aligned with sensor
coordinate X or Y (see Figure 23).
Figure 23: Package Top View with X- and Y-Axes
MA734 Rev. 1.0
5/27/2021
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MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
Determine which axis needs to be reduced
based on the qualitative field distribution around
a ring (see Figure 19 on page 18). For example,
Figure 23 shows an arrangement in which the
field along the sensor Y direction is tangential
and weaker. The X-axis should be reduced (ETX
= 1 and ETY = 0). 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 12). This reduces the sinusoidal
signal and consequently modifies the magnetic
field thresholds (see Figure 2 on page 8).
Table 14: MGLT and MGHT Binary to mT
Relationship
Field Threshold in mT (7)
MGLT or
MGHT (8)
000
001
010
011
100
101
110
111
Table 12: Trimming Direction Parameters
ETX
Enable Trimming of the X-Axis
0
Disabled
1
Enabled
ETY
Enable Trimming of the Y-Axis
0
Disabled
1
Enabled
From Low to
High Magnetic
Field
26
41
56
70
84
98
112
126
Notes:
7)
8)
9)
Magnetic Field Thresholds
The magnetic flags (MGL and MGH) indicate
that the magnetic field at the sensor position is
out of the range defined by the lower (MGLT)
and upper magnetic field thresholds (MGHT)
(see Figure 24).
Valid for VDD = 3.3V. If different, then the field threshold is
scaled by the factor VDD / 3.3V.
MGLT can be larger than MGHT.
When ETX = 1 and ETY = 1, it is possible to increase the field
thresholds by increasing BCT.
The MGL and MGH alarm flags can be read via
register 27 (bit[6] and bit[7]), and their logic state
is also given at digital output pins 11 and 16.
To read the MGL and MGH flags via the SPI,
send the 8-bit read command to register 27:
Command
0 1 0
Reg. Address
1 1 0 1 1
MGH
MGH MGL
MGL
B
MGLT
Value
MSB
LSB
0 0 0 0 0 0 0 0
The MA734 response with the register 27
content in the next transmission:
MagHys
0
From High to
Low Magnetic
Field
20
35
50
64
78
92
106
120
MGHT
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 3 bits and stored in
register 6 (see Table 13).
R[7:0]
x
x
x
x
x
x
Filter Window (FW)
The filter window (FW) determines the effective
resolution (defined as the ±3σ noise interval).
Figure 25 shows the effective resolution for
different window size (FW) and magnetic field
(B).
Table 13: Register 6
Register 6
Bit[7] Bit[6] Bit[5] Bit[4] Bit[3] Bit[2] Bit[1] Bit[0]
MGLT
MGHT
-
Table 14 shows the relationship between the 3bit values of MGLT and MGHT and the magnetic
field.
MA734 Rev. 1.0
5/27/2021
Figure 25: Resolution as a Function of Magnetic
Field and Window Size
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20
MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
Since FW modifies the filter time constant (τ), it
has an impact on the output bandwidth. The
cutoff frequency (fCUTOFF), which is the upper limit
of the bandwidth, the cutoff frequency, can be
calculated with Equation (6):
fCUTOFF = 0.38 / τ
(6)
Table 15 shows the time constant for each
window.
Table 15: Filter Window Size
Window Size
τ (µs)
fCUTOFF (Hz)
FW[3:0]
0
1
380 000
1
2
190 000
2
4
95 000
3
8
47 500
4
16
23 750
5
32
11 875
6
64
5 940
7
128
2 970
8
256
1 480
9
512
740
10 (default)
1024
380
11
2048
190
12
4096
95
13
4096
95
14
4096
95
15
4096
95
The time constant (τ) is the parameter entered in
the transfer function (1). This allows the user to
accurately model the system and analyze the
stability of a control loop.
Angle Change Interrupt (IRQ)
Pin 1 indicates when the angle changes with
respect to a reference angle. The reference can
either be a fixed value, or can be automatically
updated at each IRQ event.
Threshold
The threshold for defining a change is a relative
angle controlled by the parameter THR.
THR is coded on 8 bits (see Table 16). If THR is
greater than 180, then the IRQ flag is disabled.
MA734 Rev. 1.0
5/27/2021
Table 16: IRQ Threshold
THR[7:0]
Threshold (deg)
0
0
1
1.41
2
2.81
…
…
64
90 (default)
…
…
127
178.59
128
180 (IRQ flag only at 180)
129
181.41 (no IRQ flag)
…
…
255
358.59 (no IRQ flag)
Reference
The change is defined in relationship to a
reference angle. This angle is controlled by the
parameter REF. If the angle distance to REF
gets larger than the threshold, the IRQ pin goes
high. REF is an absolute angle coded on 8 bits
(see Table 17).
Table 17: Change Detection Fixed Reference
REF[7:0]
Reference (deg)
0
0
1
1.41
2
2.81
…
…
64
90 (default)
…
…
255
358.59
REF can be a fixed value, or can be
automatically updated at each crossing of the
threshold. Incremental change can also be
detected. Use the reference auto-refresh bit
(RAR) to select between the reference types
(see Table 18).
Table 18: Reference Auto-Refresh Mode
RAR
Reference
0 (default)
Remains fixed
1
Automatically updated
If RAR = 0, REF remains fixed (to the default
value or the user value).
If RAR = 1, REF is automatically updated each
time the threshold is crossed (see Figure 26 on
page 22). The user value is replaced by the
updated REF value, which is the sensor output
value at the moment the threshold was crossed.
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MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
REF6
REF5
Sensor
Out
Threshold
REF0 Threshold
Table 20: IRQ Pin Hysteresis Setting
HYST[5:0]
HYST (deg)
000000
0
…
…
111111
11.07
REF4
REF1
HYST[5:0] is 3 by default, which means the
hysteresis is set to 0.53° (see Table 20).
REF3
REF2
HYST[5:0] affects the hysteresis of the IRQ pin
whether IRQM is 0 or 1.
IRQ
Figure 26: IRQ Motion Profile Signal Response if
RAR = 1 and IRQM = 0 (Arrows = SPI Readings)
IRQ Mode (IRQM)
The IRQ pin can be set to logic level or latch-off
mode using the IRQM bit in register 7 (see Table
19).
Table 19: IRQ Pin Mode Parameter
IRQM
Mode
0
Latch off
1 (default)
Logic level
In latch-off mode, the IRQ pin resets on the first
SCLK rising edge of some SPI commands (i.e.
read angle, store registers to the NVM, restore
registers from the NVM, and clear status byte).
The IRQ flag does not reset when writing or
reading the registers.
In logic-level mode, the IRQ signal is updated
every 1µs, and reflects the status of the condition
(i.e. the relationship between angle output value,
angle threshold, and angle reference) in real
time (see Figure 27).
Hysteresis
REF
Sensor
Out
Threshold
Threshold
IRQ
Figure 27: IRQ Signal in Logic-Level Mode when
Hysteresis is Applied
In this mode, the IRQ signal status is not reset
when SPI reads the angle. To avoid multiple
transitions around the threshold, program an
amount of hysteresis via HYST[5:0] in register 7,
using Equation (7):
Hysteresis =
MA734 Rev. 1.0
5/27/2021
11.25°
64
HYST[5:0]
If RAR = 1 and IRQM = 1, the IRQ pin resets
immediately after being set, generating a short
pulse.
Error Flags
Register 26 contains information about the
sensor’s operational integrity, detailed below.
ERRPAR
When using 17-bit communication on the SPI
bus, the SPI write register command sent by the
controller to the sensor can be checked for parity
(unlike the other commands). The controller
sends a parity bit on the MOSI line after the 16bit command. The sensor checks the parity of
the 17-bit long command. If the parity is not
even, then the data to be written to the register
is discarded and the ERRPAR bit asserts (set to
1).
ERRMEM
The ERRMEM bit asserts (set to 1) if an SPI write
register command is sent while the NVM is busy
(NVM pin is high). To avoid raising the ERRMEM
flag, the user must ensure that no SPI write is
sent while the NVM pin is high (set to 1). It is also
recommended to check that the register value
returned by the SPI write register command
matches the desired written value (see the SPI
Write Register section on page 13).
ERRNVM
Restoring register values from the NVM is
secured by a cyclic redundancy check (CRC)
algorithm. If the generated CRC result does not
match the stored value, the ERRNVM bit being
asserted (set to 1). If any error flag is asserted,
the ERR pin is set to logic 1. Clear the error flags
and ERR pin by sending the SPI Clear Error
Flags command.
(7)
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MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
TYPICAL APPLICATION CIRCUIT
3.3V
1µF
MA734 VDD
/CS
SCLK
SPI
MISO
Host/
Master
Processor
MOSI
TEST
MGH
DI1
MGL
DI2
GND
Figure 28: Typical Application Circuit Using an SPI Interface and MGH/MGL Signals
MA734 Rev. 1.0
5/27/2021
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MA734 – 8-BIT TO 12.5-BIT DIGITAL ANGLE SENSOR
APPENDIX A: DEFINITIONS
Effective Resolution
(3σ noise level)
The smallest angle increment distinguishable from the noise. The
resolution is measured by computing three times σ (the standard
deviation in degrees) taken across 1,000 data points at a constant
position. The resolution in bits is obtained with: log2(360 / 6σ).
Refresh Rate
The rate at which new data points are stored in the output buffer.
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 lag = latency x v, where v is the angular velocity in deg/s.
Start-Up Time
The time until the sensor delivers valid data beginning at start-up.
Integral Nonlinearity
(INL)
Maximum deviation between the average sensor output (at a fixed
position) and the true mechanical angle (see Figure A1).
Figure A1: Resolution, INL, Lag
INL can be obtained from the error curve err(a) = out(a) - a, where out(a)
is the average across 1,000 sensor outputs and a is the mechanical angle
indicated by a high-precision encoder (
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