KMA36 Contactless Rotational and Linear 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 highly reliable universal magnetic position sensor for precise rotational or linear
measurement with a resolution up to 0.04 degree. These digital 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 Resistive (AMR) technology, the
KMA36 is able to determine accuractly and non-contacting 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 s leep and low
power m ode as wel l as autom atic wak e-up over I2C – m ake the KMA36 id eal for m any batter y applicat ions.
Position dat a can be tr ans m itted using a PW M or digital t wo-wire (SDA, SC L) com m unication bus . Using the
programmable parameters of this digital position sensor, the user can have access to a wide range of
configuration to ensure the maximum of freedom and functionalities.
Used as both a linear position sensor or a rotary position sensor, these KMA36 magnetoresistive sensors
designed by MEAS (Measurement Specialties) are insensitive to magnetic drift due to mechanical
tolerances, changes in temperature or thermal stress. The maintenance-free operation and high bandwidth
of this universal magnetic encoder makes it a good choice for dynamic applications in harsh environments.
KEY-FEATURES
Resolution 13 Bit / 0.04 degree
Operating power supply range of 3V to 5.5V
3.0 – 5.5V
Operating tempe rature - 25 - +85 °C
Average current 10 – 30 mA
Sleep current
1.2 mA
Data Update rate 24 – 720 Hz
I
2
C Clockrat e Up to 100 kBit/s
APPLICATIONS
Industrial en viro nment Robotics
Harsh environment Potentiometer
Handling machine Motor motion control
Machine tools
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PIN ASSIGNMENT
Pin No.
KMA36
TSSOP
Symbol Type Description
1 NC NC Not connected
2 CS I SPI interfac e chip select pin
3 DVCC_SE O Drive pin to power sensor
4 DI I SPI interfac e data in pin
5 DO O SPI interfac e data out pin
6 SCK I SPI interfac e 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 assignme nt
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, all voltages are referenced to
the power ground supply VSS. T ypical 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
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 temperat ure - 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
• Operati n g 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 Anal og Reference 2.01) VCC V
RAREF Analog Reference input resistance - 32 - kΩ
Table 2: O perating co nditions
1) Apply 2.0V at AREF for best results
Please refer to the typical application sec t ion to k no w which ex terna l components should be connected.
• AC/DC characteristics
Symbol Parameter Condition Min. Typ. Max. Unit
Iavg Average current1) 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
V
IH
Input high voltage Vcc = 5V, I OH = 10
mA 3
V
VOL Output low voltage Vcc = 5V, IOL = 10
mA 0.6 V
V
OH
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 rate1) 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)
Top=25°C ±0.3 ±1 °
ΔαH Hysteresis error H0=25 kA/m
3)
Top=25°C ±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 res olut ion 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 configurati on then updat e rate is fixed at 88Hz
3) System parameters apply only for recommended measurement setup (pleas e refer to the arrangement section)
SYSTEM OUTPUT
The system has two possible hardware output configurations: two-wire interface or analog output.
• Analog Output
The s ystem has a Pulse W idth Modulation unit with 10 bit resolut ion which can be easil y co upled with a f irst
order low-pass filter1) 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 setup2) 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.
• I2C (Digital Output)
The KMA36 has an I2C Interface unit (two-wire interface, standard I²C-bus specification defined by Philips
Semiconductors) with a n 8-bit data bus whic h can be eas il y used to retrie ve m easurem ent and conf iguration
information. (Please refer to the two-wire interface section for details)
Update rate
fdata = 1 / (1.4 msec x overs ampling / 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: Phy sica l interf a ce par amet ers
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
t
LOW
Clock low time
4.7 µs
t
r
Rise time
1 µs
t
f
Fall time
0.3 µs
t
SU: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, sto p and data timing parameters
Figure 3: Timing definitions
2)
2) Please refer to the standard I²C-bus specification defined by Philips Semiconductors for f urther infor mat ion .
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• Registers (Overview)
The KMA36 contains the following I/O registers:
Registers of the KMA36-SPI
Register
Size
Read/Write
Function
CONF
8 bit
R/W
Configuration bits
RES
16 bit
R/W
Resolution
MA
16 bit
R
Magnetic ang le
MIA
32 bit
R
Magnetic incr emental angle
Table 7: Registers of the KMA36
• I2C Bus
The KMA36 is always operating as a pure slave.
• I2C 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
• I2C 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 w ith an 8-bit data bus, it is necessary to send the high byte first and then the low byte.
In order to chan ge the KM A c onf igurat ion, four bytes shou ld be s ent t hrough the two-wire 8-b it dat a bus . T he
first three bytes correspond to the configuration and resolution registers. The last by te contains a 8-Bit Cyclic
Redundancy Check (CRC) value which can be calculated as described in the example.
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TWI - Send d ata
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 sy stem:
KCONF - Configuration
register
Bit
7
6
5
4
3
2
1
0
SLPE
-
LINE
MIAE
LPWRE
SPDE
OVS1
OVS0
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 - SLPE: Sleep mode enable
Writing this bit to one enables the sleep mode. This bit will be always set to zero by hardware.
Bit 5 - LINE: Linear mode enable
Writing this bit to one disables the rotational mode and enables the linear mode.
Bit 4 - MIAE: Incremental mode
enable
Writing this bit to one enables the incremental angle counter.
By writing it to zero, the counter mode is turned off and the counter set to 0.
Bit 3 - LPWRE: Low power mode
enable
W riting this bit to one enabl es the low pow er m ode.
Bit 2 - SPDE: Speed mode
enable
Writing this bit to one enables the fast speed mode.
Bit 1:0 - OVS1:0: 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 I2C
communication
1) Please refer to the arrangement section.
• CNT-Bit (KCONF register)
In addition , ther e is an incremental count er implemented, which can b e en ab led b y writing a on e to th e 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 consum ption can be reduced with the low power m ode accessible thro ugh 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 b its. P lease not ic e that a h ig her accuracy leads to a r educt ion of t h e u pda te rat e ( P lease r ef er to the
Update rate table)
OVS1
OVS0
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
Bit 15:0 KRES15:0:
Resolution
Table 14: KRES - Resol utio n R egist er
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 overs ampling / 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 t wo -wire inter face c onfigur ation, th e slave a ddress of the s ystem can be c onfigured b y connecting A0 and
another pin as described in following table.
TWI - Slave address configuration
Address
Connection
0x59
A0
GND
0x5A
A0
DCOILP
0x5B
A0
DCOILN
0x5C
A0
DVCC_SE
0x5D
A0
VCC
Table 15: TWI / I2C Slave address configuration
In analog m ode, the rotation direction can be configured b y connecting D VCC_SE and a p ower 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
Connection
CW
DVCC_SE
VCC
CCW
DVCC_SE
4,7K to GND
ANALOG - User selectable output fo r zero reference
Percent
Connection
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
Connection
Active
A0
COILP
Inactive
A0
-
Table 16: Analog-Mode configuratio n
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TYPICAL APPLIC ATION
• 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 res is tiv e tec hno lo g y which s e ns es the magnetic fiel d i n the s e nsor pla ne, it is ad v ised t o
mount the magnet disc centered above the sensor center. Please refer to the magnets and scales section
for more information about the magnetic center p os itio n of the KMA36. T he magnetic sc ale shou ld b e pl ac ed
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 mo de
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 develo pment purposes, MEAS offer s a magnet disc m ade of plastic bond ed Nd-Fe-B m agnetic m aterial
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.
Table 17a: Typical MEAS disc-magnet specifi cat ion
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 m agnetic ferrite tape bonde d on a s teel sup port which guarante es mechan ical stabi lity. T he 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:
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.
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
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
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PACKAGE DRAWI NG
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 4.30 4.40 4.50
e - 0.65 -
L 0.45 0.60 0.75
N - 20 -
R 0.09 - -
S 0.20 - -
Table 18: common dimensio ns
ORDERING CO DE
Product Description Article number
KMA36 KMA36 TSSOP20
G-MRMO-031
Table 19: Ordering codes
This data sheet contains data from the preliminary specification. Supplementary data will be published lat er.
Measurement Specialties res erves the right to change the specification wi thout notice, in order to improve the design
and performance of the product.
ORDERING INFORMATION
NORTH AMERICA
EUROPE
ASIA
Measurement Specialties, Inc.
1000 Lucas Way
Hampton, VA 23666
United States
Phone: +1-800-745-8008
Fax: +1-757-766-4297
Email: sales@meas-spec.com
Web: www.meas-spec.com
MEAS Deutschland GmbH
Hauert 13
D-44227 Dortmund
Germany
Phone: +49-(0)231-9740-0
Fax: +49-(0)231-9740-20
Email: info.de@meas-spec.com
Web: www.meas-spec.com
Measurement Specialties China Ltd.
No. 26, Langshan Road
High-tech Park (North)
Nanshan District, Shenzhen 518057
China
Phone: +86-755-33305088
Fax: +86-755-33305099
Email: info.cn@meas-spec.com
Web: www.meas-spec.com
The information in this sheet has been carefully reviewed and is believed to be accurate; however, no responsibility is assumed for
inaccuracies. Furtherm ore, this information does not convey to t he purchaser of s uch devices any lic ense under the patent rights to the
manufacturer. Measurement Specialties, Inc. reserves the right to make changes without further notice to any product herein.
Measurement Specialties, Inc. makes no warranty, represent ation or guarantee rega rding the sui tability of it s product for any particular
purpose, nor does Measurement Specialti es, Inc. assume any liability arising out of the applicat ion or use of any product or c ircuit and
specificall y disclaims any and all liabilit y, including without limit ation consequential or incidental damages. Typical parameters can and
do vary in different applications. All operating parameters must be validated for each customer application by customer’s technical
experts. Measurem ent Speci alti es, I nc. does not convey any license under its patent rights nor the rights of others.