KMA36 universal magnetic encoder
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Contactless Absolute 360° (180°) angle measurement
Incremental mode
Linear mode
Standard I2C Interface (100 kHz)
Programmable resolution up to 13 bit (0.04 degree)
Very low hysteresis
High accuracy mode
User programmable parameters
Low power mode
Sleep and automatic wake-up over I2C
Programmable zero position
Device address hardware configurable
Small Pb-Free package (TSSOP20)
RoHS compliant
DESCRIPTION
The KMA36 is a universal magnetic encoder for precise rotational or linear measurement. These position
sensors feature a system-on-chip technology that combines a magnetoresistive element along with analog
to digital converter and signal processing in a standard small package. By using Anisotropic Magneto Resis-
tive (AMR) technology, the KMA36 is able to determine contactlessly the magnetic angle of an external
magnet over 360°, as well as the incremental position on a magnetic pole strip with 5 mm pole length. Its
sleep and low power mode as well as automatic wake-up over I2C – make the KMA36 ideal for many
battery applications. Position data can be transmitted using a PWM or two-wire (SDA, SCL) communication
bus. Using the programmable parameters, the user can have access to a wide range of configuration to
ensure the maximum of freedom and functionalities.
KEY-FEATURES
Resolution 13 Bit / 0.04 degree
Operating power supply range of 3V to 5.5V 3.0 – 5.5V
Operating temperature - 25 - +85 °C
Average current 10 – 30 mA
Sleep current 1.2 mA
Data Update rate 24 – 720 Hz
I
2
C Clockrate Up to 100 kBit/s
APPLICATIONS
Industrial environment
Harsh environment
Handling machine
Machine tools
Robotics
Potentiometer
Motor motion control
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PIN ASSIGNMENT
Pin No.
KMA36 TSSOP
Symbol Type Description
1 A1 NC Not connected
2 A0 I Slave adress configuration pin
3 DVCC_SE O Drive pin to power sensor
4 SDA I/O Two-wire interface data pin
5 PWM O PWM output
6 SCL I Two-wire interface clock pin
7 GND_SE S Sensor supply ground pin
8 VCC_SE S Sensor power supply pin
9 NC NC Not connected
10 NC NC Not connected
11 NC NC Not connected
12 COILP I Coil power supply pin
13 COILN I Coil power supply pin
14 AREF I Asic analog reference
15 NC NC Not connected
16 GND_AS S Asic supply ground
17 NC NC Not connected
18 VCC_AS S Asic power supply
19 DCOILN O Drive pin to coil power supply
20 DCOILP O Drive pin to coil power supply
Figure 1: Pin assignment
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, all voltages are referenced to
the power ground supply VSS. Typical values are based on
Top= 25 °C, VCC = 5 V. They are given only as design
guidelines and are not tested in production. Data based on
characterization results, design simulation and/or
technology characteristics are indicated in the table
footnotes and are not tested in production.
Absolute maximum ratings are limiting values of permitted
operation and should never be exceeded under the worst
possible conditions either initially or consequently. If
exceeded by even the smallest amount, instantaneous
catastrophic failure can occur. And even if the device
continues to operate satisfactorily, its life may be
considerably shortened.
Figure 2: Functional block description
Angle
MR
Magnet
magnetic field
AMPLIFICATION
ADC
10 bit
CORE
ERROR
HANDLING
I2C
SENSOR
EVALUATION COMMUNICATION
OP AMP
PWM
MODE
HANDLING
Position
Parameter
PWM
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Absolute maximum ratings
CAUTION: Exceeding these values may destroy the product.
Symbol Parameter Condition Min. Typ. Max. Unit
Top Operating temperature - 25 + 85 °C
Tsto Storage temperature - 40 + 85 °C
Vcc Operating voltage 2.9 6 V
Vin Input voltage on any Pin Except on A1 -0.5 6.5 V
Vin Input voltage on A1 -0.5 13 V
Iin DC Current through any I/O Pin 40 mA
Iin DC Current through S Pin 200 mA
Iin DC Current through any C Pin 60 mA
Table 1: Absolute maximum ratings
Operating conditions
Symbol Parameter Condition Min. Typ. Max. Unit
Top Operating temperature - 25 + 85 °C
Vcc Operating voltage 3 5.5 V
Vin Input voltage on I/O pin -0.3 5.3 V
ARef External Analog Reference 2.0
1) VCC V
RAREF Analog Reference input resistance - 32 - kΩ
Table 2: Operating conditions
1)
Apply 2.0V at AREF for best results
Please refer to the typical application section to know which external components should be connected.
AC/DC characteristics
Symbol Parameter Condition Min. Typ. Max. Unit
Iavg Average current
1)
Except in sleep mode, Vcc = 5V 10 30 mA
Isleep Sleep current Vcc = 5V 1.2 mA
VIL Input low voltage Vcc = 5V, IOL = 10 mA 0.6 V
VIH Input high voltage Vcc = 5V, IOH = 10 mA 3 V
VOL Output low voltage Vcc = 5V, IOL = 10 mA 0.6 V
VOH Output high voltage Vcc = 5V, IOH = 10 mA 4.3 V
Table 3: AC/DC characteristics
1)
Current measurement has been done with a standard circuit including a voltage divider on AREF.
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System parameters
Symbol Parameter Condition Min. Typ. Max. Unit
fdata Update rate
1) 2) 24 720 Hz
tstart Starting time 5 ms
αr Resolution H0=25 kA/m
3)
13 Bit
ΔαL Linearity error H0=25 kA/m
3)
±0.3 ±1 °
ΔαH Hysteresis error H0=25 kA/m
3)
±0.1 ±0.25 °
Vbwn Brown-out reset voltage 2.7 V
tbwn Brown-out reset pulse width 2 µs
Hy Applied magnetic field 15 25 60 kA/m
RCOIL Internal coil resistance 75 100 150 Ω
ΔPWM PWM output resolution 10 bit
fPWM PWM frequency 7.8 kHz
Table 4: System parameters
1)
Maximum is measured in speed mode with minimum oversampling. Minimum is measured with maximum oversampling.
2)
When using the analog-output configuration then update rate is fixed at 88Hz
3)
System parameters apply only for recommended measurement setup (please refer to the arrangement section)
SYSTEM OUTPUT
The system has two possible hardware output configurations: two-wire interface or analog output.
Analog Output
The system has a Pulse Width Modulation unit with 10 bit resolution which can be easily coupled with a first
order low-pass filter
1)
to generate an analog output between Vss and Vcc corresponding to 0° and 360°. In
this hardware configuration, all internal registers are loaded with initial values. No digital configuration is
necessary, all available configurations can be set by changing the hardware setup
2)
of the KMA36.
1)
Please refer to the typical application section for further information.
2)
Please refer to the hardware configuration section for further information.
I
2
C (Digital Output)
The KMA36 has an I
2
C Interface unit (two-wire interface, standard I²C-bus specification defined by Philips
Semiconductors) with an 8-bit data bus which can be easily used to retrieve measurement and configuration
information. (Please refer to the two-wire interface section for details)
Update rate
fdata = 1 / (1.4 msec x oversampling / const)
SPD Bit const
0 1
1 2
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TWO WIRE IN INTERFACE
Physical interface parameters
Symbol Parameter Condition Min. Typ. Max. Unit
Brt Clockrate 10 50 100 kBit/s
AL Address length 7 bit
AS Address
1)
0x59 Hex
Table 5: Physical interface parameters
1)
Please refer to the hardware configuration section to determine how to configure other addresses.
Timing parameters
Symbol Parameter Condition Min. Typ. Max. Unit
tSU:STA Start setup time 4.7 µs
tHD:STA Start hold time 4.0 µs
tSU:STO Stop setup time 4.0 µs
tHIGH Clock high time 4.0 50 µs
tLOW Clock low time 4.7 µs
tr Rise time 1 µs
tf Fall time 0.3 µs
tSU:DAT Data input setup time 0.25 µs
THD:DAT Data input hold time 0.3 µs
tBUF Bus free time 4.7 µs
Table 6: Start, stop and data timing parameters
Figure 3: Timing definitions2)
2)
Please refer to the standard I²C-bus specification defined by Philips Semiconductors for further information.
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Registers (Overview)
The KMA36 contains the following I/O registers:
Register Size Read/Write Function
KCONF 8 bit R/W Configuration bits
KRES 16 bit W Resolution
MA 16 bit R Magnetic angle
ILC 32 bit R Incremental counter
Registers of the KMA36
Table 7: Registers of the KMA36
I
2
C Bus
The KMA36 is always operating as a pure slave.
I
2
C Reading data
It is possible to read up to seven bytes as described in the following figure. No special protocol is used by
the reading-data process.
TWI - Read data
Byte 0 1 2 3 4 5 6
MA0 MA1 ILC0 ILC1 ILC2 ILC3 KCONF
Read/Write R R R R R R R
Initial value 0x00 0x00 0x00 0x00 0x00 0x00 0x03
Byte 0:1 - MA1:0: Magnetic angle
Unsigned integer giving the magnetic angle in degree with the configured resolution
Byte 2:5 - ILC3:0: Incremental linear counter
Signed long giving the incremental linear counter in degree with the configured resolution.
Byte 6 - KCONF: Configuration register
Unsigned char giving the configuration register value.
Table 8: Read data
I
2
C Writing data (general)
The KMA36 can be controlled using two internal registers. The configuration (KCONF) is an 8-bit register
and the resolution (KRES) is a 16-bit register. To write the 16-bit register (KRES) through the two-wire
interface with an 8-bit data bus, it is necessary to send the high byte first and then the low byte.
In order to change the KMA configuration, four bytes should be sent through the two-wire 8-bit data bus. The
first three bytes correspond to the configuration and resolution registers. The last byte contains a 8-Bit Cyclic
Redundancy Check (CRC) value which can be calculated as described in the example.
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TWI - Send data
Byte 0 1 2 3
KCONF KRESH KRESL KCRC
Read/Write W W W W
Initial value - - - -
Byte 0: KCONF: Configuration register
Contains the desired system configuration.
Byte 1:2 - KRES: Resolution register
Contains the desired resolution.
Byte 3 - KCRC: CRC
Contains the cyclic redundancy check.
Table 9: Send data
Example
KCONF KRESH KRESL KCRC
data 0x03 0x7F 0xFF 0x7F
KCRC = 0xFF - (KCONF + KRESH + KRESL) + 0x01
KCRC = 0xFF - (0x03 + 0x7F + 0xFF) + 0x01 = 0x7F
Table 10: CRC Example
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KCONF (Configuration register)
The configuration register is used to control and monitor the status and modes of the system:
KCONF - Configuration register
Bit 7 6 5 4 3 2 1 0
SLP - LIN CNT PWR SPD OVCS1 OVSC0
Read/Write W R/W R/W R/W R/W R/W R/W R/W
Initial value 0 0 0 0 0 0 1 0
Bit 7 - SLP: Sleep mode
Writing this bit to one enables the sleep mode. This bit will be always set to zero by hardware.
Bit 5 - LIN: Mode
Writing this bit to one disables the rotational mode and enables the linear mode.
Bit 4 - CNT: Mode
Writing this bit to one enables the incremental counter mode. By writing it to zero, the counter mode is turned off.
Bit 3 - PWR: Low power mode
Writing this bit to one enables the low power mode.
Bit 2 - SPD: Speed mode
Writing this bit to one enables the fast speed mode.
Bit 1:0 - OVCS1:0: Oversampling
These bits determines the accuracy of the angle evaluation.
Table 11: KCONF – Configuration Register
The system has three possible main configurations:
Rotational measurement used to measure the angle of a rotating magnet disc centered
above the magnetic sensor center of the KMA36.
1)
Linear measurement used to measure the linear movement of the KMA36 along
a magnetic pole strip with 5mm pole length. A lookup table is used
for internal error correction
1)
Sleep mode used to power down the KMA36. Wake up is initiated by I
2
C
communication
1)
Please refer to the arrangement section.
CNT-Bit (KCONF register)
In addition, there is an incremental counter implemented, which can be enabled by writing a one to the CNT-
Bit in the KCONF register.
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SPD-Bit (KCONF register)
The measurement update rate can be increased by activating the fast mode with SPD bit. In fast mode
measurement accuracy is reduced.
Table 12: Update rate
PWR-Bit (KCONF register)
The power current consumption can be reduced with the low power mode accessible through the PWR bit.
In low power mode only 180° measurement are possible.
OVCS-Bits (KCONF register)
To increase the measurement accuracy, it is possible to configure the oversampling rate by using the
OVSCx bits. Please notice that a higher accuracy leads to a reduction of the update rate (Please refer to the
Update rate table)
OVCS1 OVSC0 Oversampling
0 0 2
0 1 4
1 0 8
1 1 32
Table 13: OVSC - Oversampling
KRES (Resolution register)
The resolution can be set to any decimal value between 1 and 32768. Any other value would lead to
unexpected system behavior.
KRES - Resolution register
Bit 15 14 13 12 11 10 9 8
KRESH KRES15 KRES14 KRES13 KRES12 KRES11 KRES10 KRES9 KRES8
KRESL KRES7 KRES6 KRES5 KRES4 KRES3 KRES2 KRES1 KRES0
Bit 7 6 5 4 3 2 1 0
Read/Write W W W W W W W W
W W W W W W W W
Initial value 0 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1
Table 14: KRES - Resolution Register
For example, a resolution of decimal 360 (0x00168) leads to rotational data in steps of 1 degree. A
resolution of decimal 3600 (0x0E10) results in steps of 0.1°.
Update rate
fdata = 1 / (1.4 msec x oversampling / const)
SPD Bit const
0 1
1 2
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HARDWARE CONFIGURATION
The hardware configuration depends on the desired output: two-wire interface or analog.
In two-wire interface configuration, the slave address of the system can be configured by connecting A0 and
another pin as described in following table.
TWI - Slave address configuration
Address
0x59 A0 GND
0x5A A0 DCOILP
0x5B A0 DCOILN
0x5C A0 DVCC_SE
0x5D A0 VCC
Connection
Table 15: TWI / I
2
C Slave address configuration
In analog mode, the rotation direction can be configured by connecting DVCC_SE and a power supply pin.
The user zero reference angle calibration can be activated by connecting A0 and COILP. When the user
zero reference angle calibration is active, the next evaluated magnetic angle will be set as the new zero
reference angle. The user selectable output voltage for the zero reference angle can be configured by
connecting A0 in series with a 4,7k ohm resistor and a port pin. The percentage indicated is relative to the
power supply value Vcc and is defined at the zero reference angle position.
ANALOG - Rotation direction configuration
Direction
CW DVCC_SE VCC
CCW DVCC_SE 4,7K to GND
ANALOG - User selectable output for zero reference
Percent
0% A0 4,7K to VCC
10% A0 4,7K to DVCC_SE
25% A0 4,7K to DCOILN
50% A0 4,7K to GND
ANALOG - Zero reference angle user calibration
Status
Active A0 COILP
Inactive A0 -
Connection
Connection
Connection
Table 16: Analog-Mode configuration
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TYPICAL APPLICATION
Electrical circuit
Figure 4: Typical circuit with two-wire interface
Figure 5: Typical circuit with analog interface
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ARRANGEMENT
Due to the magneto resistive technology which senses the magnetic field in the sensor plane, it is advised to
mount the magnet disc centered above the sensor center. Please refer to the magnets and scales section
for more information about the magnetic center position of the KMA36. The magnetic scale should be placed
perpendicularly to the KMA36 as depicted in the following figure rather in the middle along the width of the
scale. For best results the KMA36 should be as close as possible to the magnet.
Rotational (recommended) setup (for best results)
Rotational mode
Bit LIN = 0
Pay attention to the magnetic center of the KMA36
Linear setup
Linear mode
Bit LIN =1
use magnetic pole strip with 5mm pole length for best results
Figure 6: Mounting
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MAGNETS AND SCALES
Rotational Mode
The KMA36 can be used with a magnet, preferably of disc or square shape or a magnet scale with pole
pitch 5mm.
For development purposes, MEAS offers a magnet disc made of plastic bonded Nd-Fe-B magnetic material
which provides an homogenous magnetic field with sufficient magnetic field strength for typical application
with the KMA36. The following table describes typical magnets parameters. Please refer to the website
http://www.magnetfabrik.de (article number 67.044-1 ) and its application note section for more
information.
Symbol Parameter Condition Min. Typ. Max. Unit
Ø Diameter Neofer 48/60p only 14 mm
T Thickness Neofer 48/60p only 2.5 mm
Br Magnetic field strength Neofer 48/60p only 540 mT
Top Operating temperature Neofer 48/60p only 150 °C
Table 17a: Typical MEAS disc-magnet specification
Linear Mode
The linear mode of the KMA36 is designed for a magnetic scale with pole pitch 5mm. A magnetic scale is
made of a magnetic ferrite tape bonded on a steel support which guarantees mechanical stability. The steel
support is made of an optimum stainless steel alloy that provides no loss of magnetic field strength. MEAS
offers a standard scale with the following parameters for development purpose:
Symbol Parameter Condition Min. Typ. Max. Unit
LT Length MEAS magnetic scale only 1 m
LP Pole length MEAS magnetic scale only 5 mm
W Width MEAS magnetic scale only 10 mm
T Thickness MEAS magnetic scale only 1.3 mm
Δp Accuracy MEAS magnetic scale only 40 µm/m
Top Operating temperature MEAS magnetic scale only -40 100 °C
Table 17b: Typical MEAS magnet-scale specification
The correct magnet dimensions and assembly geometry depend on the specific arrangement of the
application and are part of the specification of the entire system.
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PACKAGE DRAWING
Figure 7: Package drawing (Magnetic center)
Figure 8: Package drawing
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COMMON DIMENSIONS (MILLIMETERS)
Symbol Min. Typ. Max.
A - - 1.20
A1 0.05 - 0.15
A2 0.80 1.00 1.05
b 0.19 - 0.30
D 6.40 6.50 6.60
E - 6.40 -
E1 4.
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