ams AS5245 Programmable 360⺠magnetic angle encoder with absolute ssi and pwm output Datasheet

Data Sheet
AS5245
Programmable 360º Magnetic Angle Encoder with Absolute SSI and
PWM Output
1 General Description
Two digital 12-bit absolute outputs
Quadrature A/B (10- or 12-bit) and Index output signal
The AS5245 is a contactless magnetic angle encoder for accurate
measurement up to 360º and includes two AS5145 devices in a
punched stacked leadframe.
User programmable zero position
Failure detection mode for magnet placement monitoring and
loss of power supply
It is a system-on-chip, combining integrated Hall elements, analog
front end and digital signal processing in a single device.
“Red-Yellow-Green” indicators display placement of magnet in
Z-axis
To measure the angle, only a simple two-pole magnet, rotating over
the center of the chip is required. The magnet may be placed above
or below the IC.
Tolerant to magnet misalignment and air gap variations
Wide temperature range: - 40ºC to +150ºC
The absolute angle measurement provides instant indication of the
magnet’s angular position with a resolution of 0.0879º = 4096
positions per revolution. This digital data is available as a serial bit
stream and as a PWM signal.
An internal voltage regulator allows operation of the AS5245 from
3.3V or 5.0V supplies.
The AS5245 is fully automotive qualified to AEC-Q100, grade 0.
2 Key Features
Contactless high resolution rotational position encoding over a
full turn of 360º
Unique Chip Identifier
Fully automotive qualified to AEC-Q100, grade 0
Small package: QFN 32 LD (7x7)
3 Applications
The AS5245 is ideal for applications with an angular travel range
from a few degrees up to a full turn of 360º. The device is suitable for
Automotive applications like Throttle position sensors, Gas/brake
pedal position sensing, Headlight position control, Contactless rotary
position sensing, Front panel rotary switches and Replacement of
potentiometer.
Figure 1. AS5245 Block Diagram
VDD3V3
VDD5V
MagINCn
MagDECn
LDO 3.3V
PWM
Interface
Sin
Hall Array
&
Frontend
Amplifier
Mux
Cos
PWM
Ang
DSP
Mag
Absolute
Interface
(SSI)
DO
CSn
CLK
OTP
Register
AS5245
PDIO
Incremental
Interface
DTEST1_A
DTEST2_B
Mode_Index
Note: This Block Diagram presents only one die
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AS5245
Data Sheet - C o n t e n t s
Contents
1 General Description ..................................................................................................................................................................
1
2 Key Features.............................................................................................................................................................................
1
3 Applications...............................................................................................................................................................................
1
4 Pin Assignments .......................................................................................................................................................................
4
4.1 Pin Descriptions....................................................................................................................................................................................
5
5 Absolute Maximum Ratings ......................................................................................................................................................
6
6 Electrical Characteristics...........................................................................................................................................................
7
6.1 Magnetic Input Specification.................................................................................................................................................................
8
6.2 System Specifications ..........................................................................................................................................................................
9
7 Timing Characteristics ............................................................................................................................................................
11
8 Detailed Description................................................................................................................................................................
12
8.1 Mode_Index Pin..................................................................................................................................................................................
8.2 Synchronous Serial Interface (SSI) ....................................................................................................................................................
8.2.1
8.2.2
8.2.3
8.2.4
8.2.5
8.2.6
Serial Data Contents..................................................................................................................................................................
Z-axis Range Indication (Push Button Feature, Red/Yellow/Green Indicator)...........................................................................
Incremental Mode ......................................................................................................................................................................
Sync Mode.................................................................................................................................................................................
Sine/Cosine Mode .....................................................................................................................................................................
Daisy Chain Mode .....................................................................................................................................................................
8.3 Pulse Width Modulation (PWM) Output..............................................................................................................................................
12
13
13
14
14
16
16
16
17
8.3.1 Changing the PWM Frequency.................................................................................................................................................. 18
8.4 Analog Output.....................................................................................................................................................................................
9 Application Information ...........................................................................................................................................................
19
9.1 Programming the AS5245 ..................................................................................................................................................................
9.1.1
9.1.2
9.1.3
9.1.4
9.1.5
9.1.6
18
Zero Position Programming .......................................................................................................................................................
OTP Memory Assignment..........................................................................................................................................................
User Selectable Settings ...........................................................................................................................................................
OTP Default Setting...................................................................................................................................................................
Redundancy...............................................................................................................................................................................
Redundant Programming Option ...............................................................................................................................................
9.2 Alignment Mode..................................................................................................................................................................................
19
19
20
20
21
21
21
22
9.3 3.3V / 5V Operation ............................................................................................................................................................................
23
9.4 Choosing the Proper Magnet..............................................................................................................................................................
24
9.5 Failure Diagnostics .............................................................................................................................................................................
25
9.5.1 Magnetic Field Strength Diagnosis ............................................................................................................................................ 25
9.5.2 Power Supply Failure Detection ................................................................................................................................................ 25
9.6 Angular Output Tolerances .................................................................................................................................................................
9.6.1
9.6.2
9.6.3
9.6.4
9.6.5
9.6.6
9.6.7
Accuracy ....................................................................................................................................................................................
Transition Noise.........................................................................................................................................................................
High Speed Operation ...............................................................................................................................................................
Propagation Delays ...................................................................................................................................................................
Internal Timing Tolerance ..........................................................................................................................................................
Temperature ..............................................................................................................................................................................
Accuracy over Temperature ......................................................................................................................................................
9.7 AS5245 Differences to AS5045..........................................................................................................................................................
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25
27
27
28
28
28
28
29
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AS5245
Data Sheet - C o n t e n t s
10 Package Drawings and Markings .........................................................................................................................................
30
11 Ordering Information .............................................................................................................................................................
32
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AS5245
Data Sheet - P i n A s s i g n m e n t s
4 Pin Assignments
VDD3V_Top
VDDA5V_Bottom
VDDA5V_Top
MagINCn_Top
MagINCn_Bottom
MagDECn_Top
MagDECn_Bottom
DTest1_A_Top
Figure 2. Pin Assignments (Top View)
32 31 30 29 28 27 26 25
DTest1_A_Bottom
1
24
VDD3V_Bottom
DTest2_B_Top
2
23
NC
DTest2_B_Bottom
3
22
NC
NC
4
21
NC
NC
5
20
NC
Mode_Index_Top
6
19
PWM_Top
Mode_Index_Bottom
7
18
PWM_Bottom
VSS_Top
8
17
CSn_Top
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CSn_Bottom
DO_Bottom
DO_Top
CLK_Bottom
PDIO_Top
CLK_Top
10 11 12 13 14 15 16
PDIO_Bottom
9
VSS_Bottom
AS5245
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AS5245
Data Sheet - P i n A s s i g n m e n t s
4.1 Pin Descriptions
Table 1. Pin Descriptions
Pin Name
Pin Number
Pin Type
DTest1_A
1, 32
Digital output
Test output in default mode
DTest2_B
2, 3
Digital output
Test output in default mode
NC
4, 5
-
Mode_Index
6, 7
Digital I/O pull-down
VSS
8, 9
Supply pin
PDIO
10, 11
OTP Programming Input and Data Input for Daisy Chain mode.
Digital input pull-down Internal pull-down resistor (~74kΩ). Should be connected to VSS if
programming is not used.
CLK
12, 13
Digital input, Schmitt- Clock Input of Synchronous Serial Interface; Schmitt-Trigger input
trigger input
DO
14, 15
CSn
16, 17
PWM
18, 19
Digital output
NC
20, 21
-
For internal use. Must be left unconnected
NC
22, 23
-
For internal use. Must be left unconnected
VDD3V3
24, 25
Supply pin
3V-Regulator Output for internal core, regulated from VDD5V. Connect to
VDD5V for 3V supply voltage. Do not load externally.
VDD5V
26, 27
Supply pin
Positive Supply Voltage, 3.0V to 5.5V
MagINCn
28, 29
Digital output open
drain
Magnet Field Magnitude Increase. Active low. Indicates a distance
reduction between the magnet and the device surface.
MagDECn
30, 31
Digital output open
drain
Magnet Field Magnitude Decrease. Active low. Indicates a distance
increase between the device and the magnet.
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Digital output / tristate
Description
For internal use. Must be left unconnected
Select between slow (open, low: VSS) and fast (high) mode. Internal pulldown resistor.
Negative Supply Voltage (GND)
Data Output of Synchronous Serial Interface
Digital input pull-up, Chip Select. Active low. Schmitt-Trigger input, internal pull-up resistor
Schmitt-trigger input (~50kΩ)
Pulse Width Modulation of approx. 244Hz; 1µs/step (opt. 122Hz; 2µs/
step)
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AS5245
Data Sheet - A b s o l u t e M a x i m u m R a t i n g s
5 Absolute Maximum Ratings
Stresses beyond those listed in Table 2 may cause permanent damage to the device. These are stress ratings only, and functional operation of
the device at these or any other conditions beyond those indicated in Electrical Characteristics on page 7 is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
Table 2. Absolute Maximum Ratings
Parameter
Min
Max
Units
DC supply voltage at pin VDD5V
-0.3
7
V
DC supply voltage at pin VDD3V3
-0.3
5
V
Comments
Input pin voltage
-0.3
7
V
Pins Prog, MagINCn, MagDECn, CLK, CSn
Input current (latchup immunity)
-100
100
mA
Norm: JEDEC 78
±2
kV
Norm: MIL 883 E method 3015
+150
ºC
260
ºC
Electrostatic discharge
Storage temperature
-55
Body temperature (Lead-free package)
Humidity non-condensing
5
85
%
Ambient temperature
-40
150
ºC
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t=20 to 40s, Norm: IPC/JEDEC J-Std-020C
Lead finish 100% Sn “matte tin”
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AS5245
Data Sheet - E l e c t r i c a l C h a r a c t e r i s t i c s
6 Electrical Characteristics
TAMB = -40 to +150ºC, VDD5V = 3.0-3.6V (3V operation) VDD5V = 4.5-5.5V (5V operation) unless otherwise noted.
Table 3. Electrical Characteristics
Symbol
Parameter
Condition
Min
Typ
Max
Unit
+150
ºC
16
21
mA
4.5
5.0
5.5
3.0
3.3
3.6
3.0
3.3
3.6
3.0
3.3
3.6
1.37
2.2
2.9
1.08
1.9
2.6
Operating Conditions
TAMB
Ambient temperature
Isupp
Supply current
VDD5V
Supply voltage at pin VDD5V
-40
(one die only)
VDD3V3
Voltage regulator output voltage at pin
VDD3V3
5V Operation
VDD5V
Supply voltage at pin VDD5V
VDD3V3
Supply voltage at pin VDD3V3
3.3V Operation
(pin VDD5V and VDD3V3 connected)
VON
Power-on reset thresholds
On voltage; 300mV typ. hysteresis
VOFF
Power-on reset thresholds
Off voltage; 300mV typ. hysteresis
DC supply voltage 3.3V (VDD3V3)
V
V
V
Programming Conditions
VPROG
Programming voltage
Voltage applied during programming
3.3
3.6
V
VProgOff
Programming voltage off level
Line must be discharged to this level
0
1
V
IPROG
Programming current
Current during programming
100
mA
Rprogrammed
Programmed fuse resistance (log 1)
10µA maximum current@100mV
100k
∞
Ω
Runprogrammed
Unprogrammed fuse resistance (log
0)
2mA maximum current@100mV
50
100
Ω
DC Characteristics CMOS Schmitt-Trigger Inputs: CLK, CSn (CSn = Internal Pull-up)
Normal operation
0.7 *
VDD5V
VIH
High level input voltage
V
VIL
Low level input voltage
VIon- VIoff
Schmitt Trigger hysteresis
ILEAK
Input leakage current
CLK only
-1
1
IiL
Pull-up low level input current
CSn only, VDD5V: 5.0V
-30
-100
0.7 *
VDD5V
VDD5V
V
3.3
3.6
V
0.3 *
VDD5V
V
100
µA
0.3 *
VDD5V
1
V
V
µA
DC Characteristics CMOS / Program Input: PDIO
VIH
High level input voltage
VPROG
High level input voltage
VIL
Low level input voltage
IiL
High level input current
During programming,
Either with 3.3V or 5V supply
VDD5V: 5.5V
30
DC Characteristics CMOS Output Open Drain: MagINCn, MagDECn
IOZ
Open drain leakage current
1
µA
VOL
Low level output voltage
VSS
+0.4
V
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AS5245
Data Sheet - E l e c t r i c a l C h a r a c t e r i s t i c s
Table 3. Electrical Characteristics
Symbol
Parameter
IO
Output current
Condition
Min
Typ
Max
VDD5V: 4.5V
4
VDD5V: 3V
2
Unit
mA
DC Characteristics CMOS Output: PWM
VOH
High level output voltage
VOL
Low level output voltage
IO
Output current
VDD5V–
0.5
V
VSS
+0.4
VDD5V: 4.5V
4
VDD5V: 3V
2
V
mA
DC Characteristics CMOS Output: A, B, Index
VOH
High level output voltage
VOL
Low level output voltage
IO
Output current
VDD5V–
0.5
V
VSS
+0.4
VDD5V: 4.5V
4
VDD5V: 3V
2
V
mA
DC Characteristics Tri-state CMOS Output: DO
VOH
High level output voltage
VOL
Low level output voltage
IO
Output current
IOZ
Tri-state leakage current
VDD5V–
0.5
V
VSS
+0.4
VDD5V: 4.5V
4
VDD5V: 3V
2
V
mA
1
µA
6.1 Magnetic Input Specification
TAMB = -40 to +150ºC, VDD5V = 3.0 to 3.6V (3V operation) VDD5V = 4.5 to 5.5V (5V operation) unless otherwise noted.
Two-pole cylindrical diametrically magnetized source:
Table 4. Magnetic Input Specification
Symbol
Parameter
Condition
Min
Typ
dmag
Diameter
4
6
tmag
Thickness
Recommended magnet: Ø 6mm x 2.5mm for
cylindrical magnets
Bpk
Magnetic input field amplitude
Required vertical component of the magnetic
field strength on the die’s surface, measured
along a concentric circle with a radius of
1.1mm
Boff
Magnetic offset
Field non-linearity
fmag_abs
Input frequency
(rotational speed of magnet)
Max
mm
2.5
45
Unit
mm
75
mT
Constant magnetic stray field
± 10
mT
Including offset gradient
5
%
153 rpm @ 4096 positions/rev;
fast mode
2.54
38 rpm @ 4096 positions/rev; slow mode
0.63
Hz
Disp
Displacement radius
Maximum offset between defined device
center and magnet axis
0.25
mm
Ecc
Eccentricity
Eccentricity of magnet center to rotational axis
100
µm
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AS5245
Data Sheet - E l e c t r i c a l C h a r a c t e r i s t i c s
Table 4. Magnetic Input Specification
Symbol
Parameter
Condition
Min
Typ
Recommended magnet material and
temperature drift
NdFeB (Neodymium Iron Boron)
-0.12
SmCo (Samarium Cobalt)
-0.035
Max
Unit
%/K
6.2 System Specifications
TAMB = -40 to +150ºC, VDD5V = 3.0 to3.6V (3V operation) VDD5V = 4.5 to5.5V (5V operation) unless otherwise noted.
Table 5. Input Specification
Symbol
Parameter
Condition
RES
Resolution
INLopt
INLtemp
Max
Unit
0.088 deg
12
bit
Integral non-linearity (optimum)
Maximum error with respect to the best line fit.
Centered magnet without calibration, TAMB
=25ºC.
±0.5
deg
Integral non-linearity (optimum)
Maximum error with respect to the best line fit.
Centered magnet without calibration,
TAMB = -40 to +150ºC
±0.9
deg
INL
Integral non-linearity
Best line fit = (Errmax – Errmin) / 2
Over displacement tolerance with 6mm
diameter magnet, without calibration, TAMB = 40 to +150ºC
±1.4
deg
DNL
Differential non-linearity
12bit, no missing codes
±0.044
deg
1 sigma, fast mode (MODE = 1)
0.06
TN
Transition noise
1 sigma, slow mode
(MODE = 0 or open)
0.03
Fast mode (Mode = 1);
Until status bit OCF = 1
20
Slow mode (Mode = 0 or open);
Until OCF = 1
80
Fast mode (MODE = 1)
96
Slow mode (MODE = 0 or open)
384
tPwrUp
tdelay
fS
fS
CLK/SEL
Power-up time
System propagation delay
absolute output : delay of ADC, DSP
and absolute interface
Internal sampling rate for absolute
output:
Internal sampling rate for absolute
output
Read-out frequency
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Min
Typ
ms
TAMB = 25ºC, slow mode
(MODE=0 or open)
2.48
2.61
2.74
TAMB = -40 to +150ºC, slow mode (MODE=0
or open)
2.35
2.61
2.87
TAMB = 25ºC, fast mode
(MODE = 1)
9.90
10.42
10.94
TAMB = -40 to +150ºC, fast mode
(MODE=1)
9.38
10.42
11.46
Maximum clock frequency to read out serial
data
Revision 1.3
Deg
RMS
µs
kHz
kHz
1
MHz
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AS5245
Data Sheet - E l e c t r i c a l C h a r a c t e r i s t i c s
Figure 3. Integral and Differential Non-Linearity Example
1023
α 10bit code
1023
Actual curve
2
TN
DNL+1LSB
1
0
Ideal curve
INL
0.35°
512
512
0
0°
180°
360 °
α [degrees]
Integral Non-Linearity (INL) is the maximum deviation between actual position and indicated position.
Differential Non-Linearity (DNL) is the maximum deviation of the step length from one position to the next.
Transition Noise (TN) is the repeatability of an indicated position.
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AS5245
Data Sheet - T i m i n g C h a r a c t e r i s t i c s
7 Timing Characteristics
TAMB= -40 to +150ºC, VDD5V= 3.0 to 3.6V (3V operation) VDD5V= 4.5 to 5.5V (5V operation), unless otherwise noted.
Table 6. Timing Characteristics
Symbol
Parameter
Conditions
Min
Typ
Max
Units
100
ns
Synchronous Serial Interface (SSI)
tDOactive
Data output activated (logic high)
Time between falling edge of CSn and
data output activated
tCLKFE
First data shifted to output register
Time between falling edge of CSn and
first falling edge of CLK
500
ns
TCLK/2
Start of data output
Rising edge of CLK shifts out one bit at a
time
500
ns
tDOvalid
Data output valid
Time between rising edge of CLK and
data output valid
413
ns
tDOtristate
Data output tri-state
After the last bit DO changes back to “tristate”
100
ns
tCSn
Pulse width of CSn
CSn =high; To initiate read-out of next
angular position
500
fCLK
Read-out frequency
Clock frequency to read out serial data
>0
ns
1
MHz
Pulse Width Modulation Output
fPWM
PWM frequency
Signal period = 4098µs ±10% at TAMB
= -40 to +150ºC
220
224
268
Hz
PWMIN
Minimum pulse width
Position 0d; angle 0 degree
0.90
1
1.10
µs
PWMAX
Maximum pulse width
Position 4098d; angle 359.91 degrees
3686
4096
4506
µs
tPROG
Programming time per bit
Time to prog. a singe fuse bit
10
20
µs
tCHARGE
Refresh time per bit
Time to charge the cap after tPROG
1
fLOAD
LOAD frequency
Data can be loaded at n x 2µs
500
kHz
fREAD
READ frequency
Read the data from the latch
2.5
MHz
fWRITE
WRITE frequency
Write the data to the latch
2.5
MHz
Programming Conditions
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AS5245
Data Sheet - D e t a i l e d D e s c r i p t i o n
8 Detailed Description
The AS5245 is manufactured in a CMOS standard process and uses a spinning current Hall technology for sensing the magnetic field
distribution across the surface of the chip. The integrated Hall elements are placed around the center of the device and deliver a voltage
representation of the magnetic field at the surface of the IC.
Through Sigma-Delta Analog / Digital Conversion and Digital Signal-Processing (DSP) algorithms, the AS5245 provides accurate high-resolution
absolute angular position information. For this purpose, a Coordinate Rotation Digital Computer (CORDIC) calculates the angle and the
magnitude of the Hall array signals. The DSP is also used to provide digital information at the outputs MagINCn and MagDECn that indicate
movements of the used magnet towards or away from the device’s surface. A small low cost diametrically magnetized (two-pole) standard
magnet provides the angular position information (see Figure 16).
The AS5245 senses the orientation of the magnetic field and calculates a 12-bit binary code. This code can be accessed via. a Synchronous
Serial Interface (SSI). In addition, an absolute angular representation is given by a Pulse Width Modulated signal at pin 12 (PWM). This PWM
signal output also allows the generation of a direct proportional analog voltage, by using an external Low-Pass-Filter. The AS5245 is tolerant to
magnet misalignment and magnetic stray fields due to differential measurement technique and Hall sensor conditioning circuitry.
Figure 4. Typical Arrangement of AS5245 and Magnet
8.1 Mode_Index Pin
The Mode_Index pin activates or deactivates an internal filter that is used to reduce the analog output noise. Activating the filter (Mode pin =
LOW or open) provides a reduced output noise of 0.03º rms. At the same time, the output delay is increased to 384µs. This mode is
recommended for high precision, low speed applications.
Deactivating the filter (Mode pin = HIGH) reduces the output delay to 96µs and provides an output noise of 0.06º rms. This mode is
recommended for higher speed applications.
Setting up the Mode pin affects the following parameters:
Table 7. Slow and Fast Mode Parameters
Parameter
Slow Mode (mode=low or open)
Fast Mode (mode=high, VDD=5V)
Sampling rate
2.61 kHz (384 µs)
10.42 kHz (96µs)
Transition noise (1 sigma)
≤ 0.03º rms
≤ 0.06º rms
Output delay
384µs
96µs
Maximum speed @ 4096 samples/rev
38 rpm
153 rpm
Maximum speed @ 1024 samples/rev
153 rpm
610 rpm
Maximum speed @ 256 samples/rev
610 rpm
2441 rpm
Maximum speed @ 64 samples/rev
2441 rpm
9766 rpm
Note: A change of the Mode during operation is not allowed. The setup must be constant during power up and during operation.
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AS5245
Data Sheet - D e t a i l e d D e s c r i p t i o n
8.2 Synchronous Serial Interface (SSI)
Figure 5. Synchronous Serial Interface with Absolute Angular Position Data
tCLKFE
CSn
TCLK/2
tCLKFE
tCSn
1
CLK
DO
D11
8
D10 D9
D8
D7
D6
D5
D4
D3
D2
D1
D0 OCF COF
Mag Mag
LIN INC DEC
tDO valid
tDO active
1
18
Even
PAR
D11
tDO Tristate
Angular Position Data
Status Bits
If CSn changes to logic low, Data Out (DO) will change from high impedance (tri-state) to logic high and the read-out will be initiated.
After a minimum time tCLK FE, data is latched into the output shift register with the first falling edge of CLK.
Each subsequent rising CLK edge shifts out one bit of data.
The serial word contains 18 bits, the first 12 bits are the angular information D[11:0], the subsequent 6 bits contain system information,
about the validity of data such as OCF, COF, LIN, Parity and Magnetic Field status (increase/decrease).
A subsequent measurement is initiated by a “high” pulse at CSn with a minimum duration of tCSn.
8.2.1
Serial Data Contents
D11:D0 – Absolute angular position data (MSB is clocked out first).
OCF – (Offset Compensation Finished). Logic high indicates the finished Offset Compensation Algorithm.
COF – (Cordic Overflow). Logic high indicates an out of range error in the CORDIC part. When this bit is set, the data at D9:D0 is invalid. The
absolute output maintains the last valid angular value. This alarm may be resolved by bringing the magnet within the X-Y-Z tolerance limits.
LIN – (Linearity Alarm). Logic high indicates that the input field generates a critical output linearity. When this bit is set, the data at D9:D0 may still
be used, but can contain invalid data. This warning may be resolved by bringing the magnet within the X-Y-Z tolerance limits.
Even Parity – Bit for transmission error detection of bits 1…17 (D11…D0, OCF, COF, LIN, MagINC, MagDEC). Placing the magnet above the
chip, angular values increase in clockwise direction by default.
Data D11:D0 is valid, when the status bits have the following configurations:
Table 8. Status Bit Outputs
OCF
1
COF
0
LIN
Mag INC
Mag DEC
0
0
0
1
1
0
1
1
0
Parity
Even checksum of bits
1:15
Note: MagInc=MagDec=1 is only recommended in YELLOW mode (see Table 9)
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8.2.2
Z-axis Range Indication (Push Button Feature, Red/Yellow/Green Indicator)
The AS5245 provides several options of detecting movement and distance of the magnet in the Z-direction. Signal indicators MagINCn and
MagDECn are available both as hardware pins (pins #1 and 2) and as status bits in the serial data stream (see Figure 5). Additionally, an OTP
programming option is available with bit MagCompEn that enables additional features:
In the default state, the status bits MagINC, MagDec and pins MagINCn, MagDECn have the following function:
Table 9. Magnetic Field Strength Red-Yellow-Green Indicator (OTP option)
Status Bits
Hardware Pins
OPT: Mag CompEn = 1 (Red-Yellow-Green Programming Option)
Mag
INC
Mag
DEC
LIN
Mag
INCn
Mag
DECn
0
0
0
Off
Off
No distance change
Magnetic input field OK (GREEN range, ~45…75mT)
1
1
0
On
Off
YELLOW range: magnetic field is ~ 25…45mT or ~75…135mT. The AS5245
may still be operated in this range, but with slightly reduced accuracy.
1
1
1
On
On
RED range: magnetic field is ~<25mT or >~135mT. It is still possible to
operate the AS5245 in the red range, but not recommended.
n/a
n/a
Not available
All other combinations
Description
Note: Pin 1 (MagINCn) and pin 2 (MagDECn) are active low via. open drain output and require an external pull-up resistor. If the magnetic
field is in range, both outputs are turned off.
The two pins may also be combined with a single pull-up resistor. In this case, the signal is high when the magnetic field is in range. It is low in all
other cases (see Table 9).
8.2.3
Incremental Mode
The AS5245 has an internal interpolator block. This function is used if the input magnetic field is too fast and a code position is missing. In this
case an interpolation is done.
With the OTP bits OutputMd0 and OutputMd1 a specific mode can be selected. For the available pre-programmed incremental versions (10bit
and 12bit), these bits are set during test at austriamicrosystems. These settings are permanent and can not be recovered.
A change of the incremental mode (WRITE command) during operation could cause problems. A power-on-reset in between is recommended.
During operation in incremental mode it is recommended setting CSn = High, to disable the SSI-Interface.
Table 10. Incremental Resolution
Mode
Description
Output
Md1
Default mode
AS5245 function DTEST1_A and
DTEST2_B are not used. The
Mode_Index pin is used for selection of
the decimation rate (low speed/high
speed).
0
0
0
1
10 bit
Incremental
mode
(low DNL)
12 bit
Incremental
mode (high
DNL)
Sync mode
Output
Md0
DTEST1_A and DTEST2_B are used as
A and B signal. In this mode the
Mode_Index Pin is switched from input
to output and will be the Index Pin. The
decimation rate is set to 64 (fast mode)
and cannot be changed from external.
1
0
In this mode a control signal is switched
to DTEST1_A and DTEST2_B.
1
1
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Resolution
DTest1_A
and
DTest2_B
Pulses
10
256
Index Width
1/3
LSB
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Figure 6. Incremental Output
Programmed
Zero Position
ClockWise
Counter ClockWise
D Test1_A
D Test2_B
1 LSB
Mode_Index
3 LSB
The hysteresis trimming is done at the final test (factory trimming) and set to 4 LSB, related to a 12 bit number.
Incremental Output Hysteresis. To avoid flickering incremental outputs at a stationary magnet position, a hysteresis is introduced. In case
of a rotational direction change, the incremental outputs have a hysteresis of 4 LSB. Regardless of the programmed incremental resolution, the
hysteresis of 4 LSB always corresponds to the highest resolution of 12 bit. In absolute terms, the hysteresis is set to 0.35 degrees for all
resolutions. For constant rotational directions, every magnet position change is indicated at the incremental outputs (see Figure 7). For example,
if the magnet turns clockwise from position “x+3“ to “x+4“, the incremental output would also indicate this position accordingly. A change of the
magnet’s rotational direction back to position “x+3“ means that the incremental output still remains unchanged for the duration of 4 LSB, until
position “x+2“is reached. Following this direction, the incremental outputs will again be updated with every change of the magnet position.
Figure 7. Hysteresis Window for Incremental Outputs
Incremental
Output
Indication
Hysteresis :
0.35°
X +6
X +5
X +4
X +3
X +2
X +1
X
X
X +1 X +2 X +3 X +4 X +5 X +6
Magnet Position
Clockwise Direction
Counterclockwise Direction
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Incremental Output Validity. During power on the incremental output is kept stable high until the offset compensation is finished and the
CSn is low (internal Pull Up) the first time. In quadrature mode A = B = Index = high indicates an invalid output. If the interpolator recognizes a
difference larger than 128 steps between two samples, it holds the last valid state. The interpolator synchronizes up again with the next valid
difference. This avoids undefined output burst, e.g. if no magnet is present.
8.2.4
Sync Mode
This mode is used to synchronize the external electronic with the AS5245. In this mode, two signals are provided at the pins DTEST1_A and
DTEST2_B. By setting of Md0=1 and Md1=1 in the OTP register, the Sync mode will be activated.
Figure 8. DTest1_A and DTest2_B
400µs (100µs)
DTest1_A
DTest1_B
Every rising edge at DTEST1_A indicates that new data in the device is available. With this signal it is possible to trigger an external customer
Microcontroller (interrupt) and start the SSI readout. DTEST2_B indicates the phase of available data.
8.2.5
Sine/Cosine Mode
This mode can be enabled by setting the OTP Factory-bit FS2. If this mode is activated, the 16 bit sinus and 16 bit cosines digital data of both
channels will be switched out. Due to the high resolution of 16 bits of the data stream, an accurate calculation can be done externally. In this
mode, the open drain outputs of DTEST1_A and DTEST2_B are switched to push-pull mode. At Pin MagDECn the clock impulse, at Pin
MagINCn the Enable pulse will be switched out. The pin PWM indicates, which phase of signal is being presented. The mode is not available in
the default mode.
8.2.6
Daisy Chain Mode
The Daisy Chain mode allows connection of several AS5245s in series, while still keeping just one digital input for data transfer (see “Data IN” in
Figure 9). This mode is accomplished by connecting the data output (DO; pin 9) to the data input (PDIO; pin 8) of the subsequent device. The
serial data of all connected devices is read from the DO pin of the first device in the chain. The length of the serial bit stream increases with every
connected device, it is n * (18+1) bits: n= number of devices. E.g. 38 bit for two devices, 57 bit for three devices, etc.
The last data bit of the first device (Parity) is followed by a dummy bit and the first data bit of the second device (D11), etc. (see Figure 10).
Figure 9. Daisy Chain Hardware Configuration
AS5145
AS5145
µC
st
1 Device
Data IN
DO
CSn
PDIO
CLK
2
nd
DO
CSn
Device
PDIO
CLK
AS5145
last Device
DO
CSn
PDIO
CLK
CLK
CSn
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Data Sheet - D e t a i l e d D e s c r i p t i o n
Figure 10. Daisy Chain Mode Data Transfer
CSn
TCLK/2
tCLK FE
1
CLK
8
D11 D10 D9
DO
D8
D7
D6
D5
D4
18
D3
D2
D1
D0 OCF COF LIN
Mag Mag Even
INC DEC PAR
D
1
2
3
D11 D10 D9
tDO valid
Angular Position Data
tDO active
Status Bits
Angular Position Data
nd
2 Device
st
1 Device
8.3 Pulse Width Modulation (PWM) Output
The AS5245 provides a pulse width modulated output (PWM), whose duty cycle is proportional to the measured angle. For angle position 0 to
4094:
t on ⋅ 4098
Position = ------------------------- – 1
( t on + t off )
(EQ 1)
Examples:
1. An angle position of 180º will generate a pulse width ton = 2049µs and a pause tOFF of 2049 µs resulting in Position = 2048 after the
calculation: 2049 * 4098 / (2049 + 2049) -1 = 2048
2. An angle position of 359.8º will generate a pulse width ton = 4095µs and a pause tOFF of 3 µs resulting in Position = 4094 after the calculation: 4095 * 4098 / (4095 + 3) -1 = 4094
Exception:
1. An angle position of 359.9º will generate a pulse width ton = 4097µs and a pause tOFF of 1 µs resulting in Position = 4096 after the calculation: 4097 * 4098 / (4097 + 1) -1 = 4096
The PWM frequency is internally trimmed to an accuracy of ±5% (±10% over full temperature range). This tolerance can be cancelled by
measuring the complete duty cycle as shown above.
Figure 11. PWM Output Signal
Angle
PWMIN
0 deg
(Pos 0)
1µs
4097µs
PWMAX
359.91 deg
(Pos 4095)
4096µs
1/fPWM
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8.3.1
Changing the PWM Frequency
The PWM frequency of the AS5245 can be divided by two by setting a bit (PWMhalfEN) in the OTP register (see Programming the AS5245 on
page 19). With PWMhalfEN = 0, the PWM timing is as shown in Table 11:
Table 11. PWM Signal Parameters (default mode)
Symbol
Parameter
Typ
Unit
Note
fPWM
PWM frequency
244
Hz
Signal period: 4097µs
PWMIN
MIN pulse width
1
µs
- Position 0d
- Angle 0 deg
PWMAX
MAX pulse width
4096
µs
- Position 4095d
- Angle 359,91 deg
When PWMhalfEN = 1, the PWM timing is as shown in Table 12:
Table 12. PWM Signal Parameters with Half Frequency (OTP option)
Symbol
Parameter
Typ
Unit
Note
fPWM
PWM frequency
2
µs
- Position 0d
- Angle 0 deg
PWMIN
MIN pulse width
8192
µs
- Position 4095d
- Angle 359,91 deg
PWMAX
MAX pulse width
2
µs
- Position 0d
- Angle 0 deg
8.4 Analog Output
An analog output can be generated by averaging the PWM signal, using an external active or passive low pass filter. The analog output voltage
is proportional to the angle: 0º= 0V; 360º = VDD5V.
Using this method, the AS5245 can be used as direct replacement of potentiometers.
Figure 12. Simple 2nd Order Passive RC Low Pass Filter
Pin12
R2
R1
analog out
PWM
VDD
C1
C2
0V
Pin7
0º
360º
VSS
Figure 12 shows an example of a simple passive low pass filter to generate the analog output.
R1,R2 ≥ 4k7
C1,C2 ≥ 1µF / 6V
(EQ 2)
R1 should be greater than or equal to 4k7 to avoid loading of the PWM output. Larger values of Rx and Cx will provide better filtering and less
ripple, but will also slow down the response time.
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Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
9 Application Information
The benefits of AS5245 are as follows:
Complete system-on-chip
Angle measurement with programmable range up to 360º
High reliability due to non-contact magnetic sensing
Ideal for applications in harsh environments
Robust system, tolerant to magnet misalignment, airgap variations, temperature variations and external magnetic fields
No calibration required
Building of redundancy systems with plausibility checks
9.1 Programming the AS5245
After power-on, programming the AS5245 is enabled with the rising edge of CSn with PDIO = high and CLK = low.
The AS5245 programming is a one-time programming (OTP) method, based on poly silicon fuses. The advantage of this method is that a
programming voltage of only 3.3V to 3.6V is required for programming.
The OTP consists of 52 bits, of which 21 bits are available for user programming. The remaining 31 bits contain factory settings and a unique
chip identifier (Chip-ID).
A single OTP cell can be programmed only once. Per default, the cell is “0”; a programmed cell will contain a “1”. While it is not possible to reset
a programmed bit from “1” to “0”, multiple OTP writes are possible, as long as only unprogrammed “0”-bits are programmed to “1”.
Independent of the OTP programming, it is possible to overwrite the OTP register temporarily with an OTP write command at any time. This
setting will be cleared and overwritten with the hard programmed OTP settings at each power-up sequence or by a LOAD operation. Use
application note AN514X_10 to get more information about the programming options.
The OTP memory can be accessed in the following ways:
Load Operation: The Load operation reads the OTP fuses and loads the contents into the OTP register. A Load operation is automatically
executed after each power-on-reset.
Write Operation: The Write operation allows a temporary modification of the OTP register. It does not program the OTP. This operation can
be invoked multiple times and will remain set while the chip is supplied with power and while the OTP register is not modified with another
Write or Load operation.
Read Operation: The Read operation reads the contents of the OTP register, for example to verify a Write command or to read the OTP
memory after a Load command.
Program Operation: The Program operation writes the contents of the OTP register permanently into the OTP ROM.
Analog Readback Operation: The Analog Readback operation allows a quantifiable verification of the programming. For each
programmed or unprogrammed bit, there is a representative analog value (in essence, a resistor value) that is read to verify whether a bit
has been successfully programmed or not.
9.1.1
Zero Position Programming
Zero position programming is an OTP option that simplifies assembly of a system, as the magnet does not need to be manually adjusted to the
mechanical zero position. Once the assembly is completed, the mechanical and electrical zero positions can be matched by software. Any
position within a full turn can be defined as the permanent new zero position.
For zero position programming, the magnet is turned to the mechanical zero position (e.g. the “off”-position of a rotary switch) and the actual
angular value is read.
This value is written into the OTP register bits Z35:Z46.
Note: The zero position value may also be modified before programming, e.g. to program an electrical zero position that is 180º (half turn)
from the mechanical zero position, just add 2048 to the value read at the mechanical zero position and program the new value into the
OTP register.
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Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
9.1.2
OTP Memory Assignment
Symbol
Function
mbit1
Factory Bit 1
51
PWMhalfEN_Index width
PMW frequency Index pulse width
50
MagCompEn
Alarm mode
49
pwmDIS
Disable PWM
48
Output Md0
Default, 10 bit inc, 12 bit inc
47
Output Md1
Sync mode
46
Z0
:
:
35
Z11
34
CCW
33
RA0
:
:
29
RA4
28
FS 0
27
FS 1
26
FS 2
25
FS 3
24
FS 4
23
FS 5
:
:
20
FS 9
17
ChipID0
16
ChipID1
:
:
0
ChipID17
12 bit Zero Position
Direction
Factory Bit
18 bit Chip ID
mbit0
9.1.3
Factory Section
Redundancy Address
ID Section
Bit
Customer Section
Table 13. OTP Bit Assignment
Factory Bit 0
User Selectable Settings
The AS5245 allows programming of the following user selectable options:
- PWMhalfEN_Indexwidth: Setting this bit, the PWM pulse will be divided by 2, in case of quadrature incremental mode A/B/Index setting
of Index impulse width from 1 LSB to 3LSB.
- MagCompEN: The green/yellow mode can be enabled by setting of this bit.
- Output Md0: Setting this bit enables sync- or 10bit incremental mode (see Table 10)
- Output Md1: Setting this bit enables sync- or 12bit incremental mode (see Table 10)
- Z [11:0]: Programmable Zero / Index Position
- CCW: Counter Clockwise Bit
ccw=0 – angular value increases in clockwise direction
ccw=1 – angular value increases in counterclockwise direction
- RA [4:0]: Redundant Address: an OTP bit location addressed by this address is always set to “1” independent of the corresponding original OTP bit setting
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Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
9.1.4
OTP Default Setting
The AS5245 can also be operated without programming. The default, un-programmed setting is:
-
9.1.5
Output Md0, Output MD1: 00= Default mode
Z0 to Z11: 00 = no programmed zero position
CCW: 0 = clockwise operation
RA4 to RA0:0 = no OTP bit is selected
MagCompEN: 1 = The green / yellow mode is enabled.
Redundancy
For a better programming reliability, a redundancy is implemented. This function can be used in cases where the programming of one bit fails.
With an address RA(4:0), one bit can be selected and programmed.
pwmDIS
0
0
0
00001
1
0
0
0
00010
0
1
0
00011
0
0
1
00100
0
0
00101
0
0
Output Md1
MagCompEN
00000
Output Md0
Address
PWMhalfEN_Indexwidth
Table 14. Redundancy Addressing
Z0
Z1
Z2
Z3
Z4
Z5
Z6
Z7
Z8
Z9
Z10
Z11
CCW
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
00110
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
00111
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
01000
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
01001
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
01010
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
01011
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
01100
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
01101
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
01110
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
01111
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
10000
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
10001
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
10010
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
10101
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
9.1.6
Redundant Programming Option
In addition to the regular programming, a redundant programming option is available. This option allows that one selectable OTP bit can be set
to “1” (programmed state) by writing the location of that bit into a 5-bit address decoder. This address can be stored in bits RA4…RA0 in the OTP
user settings.
Example: setting RA4…0 to “00001” will select bit 51 = PWhalfEN_Indexwidth, “00010” selects bit 50 = MagCompEN, “10010” selects bit 34
=CCW, etc.
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Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
9.2 Alignment Mode
The alignment mode simplifies centering the magnet over the center of the chip to gain maximum accuracy.
Alignment mode can be enabled with the falling edge of CSn while PDIO = logic high (see Figure 13). The Data bits D11-D0 of the SSI change to
a 12-bit displacement amplitude output. A high value indicates large X or Y displacement, but also higher absolute magnetic field strength. The
magnet is properly aligned, when the difference between highest and lowest value over one full turn is at a minimum.
Under normal conditions, a properly aligned magnet will result in a reading of less than 128 over a full turn.
The MagINCn and MagDECn indicators will be = 1 when the alignment mode reading is < 128. At the same time, both hardware pins MagINCn
(#1) and MagDECn (#2) will be pulled to VSS. A properly aligned magnet will therefore produce a MagINCn = MagDECn = 1 signal throughout a
full 360º turn of the magnet.
Stronger magnets or short gaps between magnet and IC may show values larger than 128. These magnets are still properly aligned as long as
the difference between highest and lowest value over one full turn is at a minimum.
The Alignment mode can be reset to normal operation by a power-on-reset (disconnect / re-connect power supply) or by a falling edge on CSn
with PDIO = low.
Figure 13. Enabling the Alignment Mode
PDIO
CSn
2µs
min.
AlignMode enable
Read-out
via SSI
exit AlignMode
Read-out
via SSI
2µs
min.
Figure 14. Exiting Alignment Mode
PDIO
CSn
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Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
9.3 3.3V / 5V Operation
The AS5245 operates either at 3.3V ±10% or at 5V ±10%. This is made possible by an internal 3.3V Low-Dropout (LDO) Voltage regulator. The
internal supply voltage is always taken from the output of the LDO, meaning that the internal blocks are always operating at 3.3V.
For 3.3V operation, the LDO must be bypassed by connecting VDD3V3 with VDD5V (see Figure 15).
For 5V operation, the 5V supply is connected to pin VDD5V, while VDD3V3 (LDO output) must be buffered by a 1...10µF capacitor, which is
supposed to be placed close to the supply pin (see Figure 15).
Note: The VDD3V3 output is intended for internal use only. It must not be loaded with an external load.
The output voltage of the digital interface I/O’s corresponds to the voltage at pin VDD5V, as the I/O buffers are supplied from this pin.
Figure 15. Connections for 5V / 3.3V Supply Voltages
5V Operation
3.3V Operation
1... 10µF
VDD3V3
VDD3V3
100n
VDD5V
100n
LDO
Internal
VDD
VDD5V
LDO
Internal
VDD
DO
DO
4.5 - 5.5V
VSS
I
N
T
E
R
F
A
C
E
PWM
+
-
-
+
CLK
3.0 - 3.6V
CSn
PDIO
VSS
I
N
T
E
R
F
A
C
E
PWM
CLK
CSn
PDIO
A buffer capacitor of 100nF is recommended in both cases close to pin VDD5V. Note that pin VDD3V3 must always be buffered by a capacitor. It
must not be left floating, as this may cause an instable internal 3.3V supply voltage, which may lead to larger than normal jitter of the measured
angle.
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Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
9.4 Choosing the Proper Magnet
Typically, the magnet should be 6mm in diameter and ≥ 2.5mm in height. Magnetic materials such as rare earth AlNiCo/SmCo5 or NdFeB are
recommended. The magnetic field strength perpendicular to the die surface has to be in the range of ±45mT…±75mT (peak).
The magnet’s field strength should be verified using a gauss-meter. The magnetic field Bv at a given distance, along a concentric circle with a
radius of 1.1mm (R1), should be in the range of ±45mT…±75mT (see Figure 16).
Figure 16. Typical Magnet (6x3mm) and Magnetic Field Distribution
typ. 6mm diameter
N
S
Magnet axis
Magnet axis
R1
Vertical field
component
R1 concentric circle;
radius 1.1mm
Vertical field
component
Bv
(45…75mT)
0
360
360
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Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
9.5 Failure Diagnostics
The AS5245 also offers several diagnostic and failure detection features, which are discussed in detail further in the document.
9.5.1
Magnetic Field Strength Diagnosis
By Software: The MagINC and MagDEC status bits will both be high when the magnetic field is out of range.
By Hardware: Pins #1 (MagINCn) and #2 (MagDECn) are open-drain outputs and will both be turned on (= low with external pull-up resistor)
when the magnetic field is out of range. If only one of the outputs are low, the magnet is either moving towards the chip (MagINCn) or away from
the chip (MagDECn).
9.5.2
Power Supply Failure Detection
By Software: If the power supply to the AS5245 is interrupted, the digital data read by the SSI will be all “0”s. Data is only valid, when bit OCF is
high, hence a data stream with all “0”s is invalid. To ensure adequate low levels in the failure case, a pull-down resistor (~10kΩ) should be added
between pin DIO and VSS at the receiving side.
By Hardware: The MagINCn and MagDECn pins are open drain outputs and require external pull-up resistors. In normal operation, these pins
are high ohmic and the outputs are high (see Table 9). In a failure case, either when the magnetic field is out of range of the power supply is
missing, these outputs will become low. To ensure adequate low levels in case of a broken power supply to the AS5245, the pull-up resistors
(~10kΩ) from each pin must be connected to the positive supply at pin 16 (VDD5V).
By Hardware, PWM Output: The PWM output is a constant stream of pulses with 1kHz repetition frequency. In case of power loss, these pulses
are missing.
9.6 Angular Output Tolerances
9.6.1
Accuracy
Accuracy is defined as the error between measured angle and actual angle. It is influenced by several factors:
The non-linearity of the analog-digital converters,
Internal gain and mismatch errors,
Non-linearity due to misalignment of the magnet.
As a sum of all these errors, the accuracy with centered magnet = (Errmax – Errmin)/2 is specified as better than ±0.5 degrees @ 25ºC (see
Figure 19).
Misalignment of the magnet further reduces the accuracy. Figure 18 shows an example of a 3D-graph displaying non-linearity over XYmisalignment. The center of the square XY-area corresponds to a centered magnet (see dot in the center of the graph). The X- and Y- axis
extends to a misalignment of ±1mm in both directions. The total misalignment area of the graph covers a square of 2x2 mm (79x79mil) with a
step size of 100µm.
For each misalignment step, the measurement as shown in Figure 19 is repeated and the accuracy (Errmax – Errmin)/2 (e.g. 0.25º in Figure 19) is
entered as the Z-axis in the 3D-graph.
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AS5245
Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
Figure 17. Example of Linearity Error Over XY Misalignment
6
5
4
° 3
800
500
2
200
1
-100
x
-1000
-1000
-800
-600
-400
-200
y
-700
0
200
-400
400
600
800
1000
0
The maximum non-linearity error on this example is better than ±1 degree (inner circle) over a misalignment radius of ~0.7mm. For volume
production, the placement tolerance of the IC within the package (±0.235mm) must also be taken into account. The total nonlinearity error over
process tolerances, temperature and a misalignment circle radius of 0.25mm is specified better than ±1.4 degrees. The magnet used for this
measurement was a cylindrical NdFeB (Bomatec® BMN-35H) magnet with 6mm diameter and 2.5mm in height.
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AS5245
Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
Figure 18.
Example of Linearity Error Over 360º
0.5
0.4
0.3
0.2
transition noise
0.1
Err max
0
-0.1
1
55
109
163
217
271
325
379
433
487
541
595
649
703
757
811
865
919
973
Err min
-0.2
-0.3
-0.4
-0.5
9.6.2
Transition Noise
Transition noise is defined as the jitter in the transition between two steps. Due to the nature of the measurement principle (Hall sensors +
Preamplifier + ADC), there is always a certain degree of noise involved. This transition noise voltage results in an angular transition noise at the
1
outputs. It is specified as 0.06 degrees rms (1 sigma) in fast mode (pin MODE = high) and 0.03 degrees rms (1 sigma) in slow mode (pin MODE
= low or open). This is the repeatability of an indicated angle at a given mechanical position. The transition noise has different implications on the
type of output that is used:
Absolute Output; SSI Interface: The transition noise of the absolute output can be reduced by the user by implementing averaging of
readings. An averaging of 4 readings will reduce the transition noise by 6dB or 50%, e.g. from 0.03º rms to 0.015º rms (1 sigma) in slow
mode.
PWM Interface: If the PWM interface is used as an analog output by adding a low pass filter, the transition noise can be reduced by lowering the cutoff frequency of the filter. If the PWM interface is used as a digital interface with a counter at the receiving side, the transition
noise may again be reduced by averaging of readings.
Incremental Mode: In incremental mode, the transition noise influences the period, width and phase shift of the output signals A, B and
Index. However, the algorithm used to generate the incremental outputs guarantees no missing or additional pulses even at high speeds (up
to 30.000 rpm and higher).
9.6.3
High Speed Operation
Sampling Rate. The AS5245 samples the angular value at a rate of 2.61k (slow mode) or 10.42k (fast mode, selectable by pin MODE)
samples per second. Consequently, the absolute outputs are updated each 384µs (96µs in fast mode). At a stationary position of the magnet,
the sampling rate creates no additional error.
Absolute Mode. At a sampling rate of 2.6kHz/10.4kHz, the number of samples (n) per turn for a magnet rotating at high speed can be
calculated by,
nslowomode =
nfastmode =
60
---------------------------------rpm ⋅ ( 384 )μs
(EQ 3)
60 -------------------------rmp ⋅ 96μs
(EQ 4)
The upper speed limit in slow mode is ~6.000rpm and ~30.000rpm in fast mode. The only restriction at high speed is that there will be fewer
samples per revolution as the speed increases (see Table 7). Regardless of the rotational speed, the absolute angular value is always sampled
at the highest resolution of 12 bit.
1. Statistically, 1 sigma represents 68.27% of readings; 3 sigma represents 99.73% of readings.
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AS5245
Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
Incremental Mode. Incremental encoders are usually required to produce no missing pulses up to several thousand rpms. Therefore, the
AS5245 has a built-in interpolator, which ensures that there are no missing pulses at the incremental outputs for rotational speeds of up to
30.000 rpm, even at the highest resolution of 10 bits (512 pulses per revolution).
9.6.4
Propagation Delays
The propagation delay is the delay between the time that the sample is taken until it is converted and available as angular data. This delay is
96µs in fast mode and 384µs in slow mode.
Using the SSI interface for absolute data transmission, an additional delay must be considered, caused by the asynchronous sampling (0 … 1/
fsample) and the time it takes the external control unit to read and process the angular data from the chip (maximum clock rate = 1MHz, number
of bits per reading = 18).
Angular Error Caused by Propagation Delay. A rotating magnet will cause an angular error caused by the output propagation delay.
This error increases linearly with speed:
esampling = rpm * 6 * prop.delay
(EQ 5)
Where:
esampling = angular error [º]
rpm = rotating speed [rpm]
prop.delay = propagation delay [seconds]
Note: Since the propagation delay is known, it can be automatically compensated by the control unit processing the data from the AS5245.
9.6.5
Internal Timing Tolerance
The AS5245 does not require an external ceramic resonator or quartz. All internal clock timings for the AS5245 are generated by an on-chip RC
oscillator. This oscillator is factory trimmed to ±5% accuracy at room temperature (±10% over full temperature range). This tolerance influences
the ADC sampling rate and the pulse width of the PWM output:
Absolute Output; SSI Interface: A new angular value is updated every 96µs (typ) in fast mode and every 384µs (typ) in slow mode.
PWM Output: A new angular value is updated every 400µs (typ). The PWM pulse timings tON and tOFF also have the same tolerance as
the internal oscillator. If only the PWM pulse width tON is used to measure the angle, the resulting value also has this timing tolerance.
However, this tolerance can be cancelled by measuring both tON and tOFF and calculating the angle from the duty cycle (see Pulse Width
Modulation (PWM) Output on page 17).
Incremental Mode: In incremental mode, the transition noise influences the period, width and phase shift of the output signals A, B and
Index. However, the algorithm used to generate the incremental outputs guarantees no missing or additional pulses even at high speeds (up
to 30.000 rpm and higher).
t on ⋅ 4097
Position = ------------------------- – 1
( t on + t off )
9.6.6
(EQ 6)
Temperature
Magnetic Temperature Coefficient. One of the major benefits of the AS5245 compared to linear Hall sensors is that it is much less
sensitive to temperature. While linear Hall sensors require a compensation of the magnet’s temperature coefficients, the AS5245 automatically
compensates for the varying magnetic field strength over temperature. The magnet’s temperature drift does not need to be considered, as the
AS5245 operates with magnetic field strengths from ±45…±75mT.
Example:
A NdFeB magnet has a field strength of 75mT @ -40ºC and a temperature coefficient of -0.12% per Kelvin. The temperature change is from -40º
to +125º = 165K.The magnetic field change is: 165 x -0.12% = -19.8%, which corresponds to 75mT at -40ºC and 60mT at 125ºC.
The AS5245 can compensate for this temperature related field strength change automatically, no user adjustment is required.
9.6.7
Accuracy over Temperature
The influence of temperature in the absolute accuracy is very low. While the accuracy is less than or equal to ±0.5º at room temperature, it may
increase to less then or equal to ±0.9º due to increasing noise at high temperatures.
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AS5245
Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
Timing Tolerance over Temperature. The internal RC oscillator is factory trimmed to ±5%. Over temperature, this tolerance may increase
to ±10%. Generally, the timing tolerance has no influence in the accuracy or resolution of the system, as it is used mainly for internal clock
generation. The only concern to the user is the width of the PWM output pulse, which relates directly to the timing tolerance of the internal
oscillator. This influence, however, can be cancelled by measuring the complete PWM duty cycle instead of just the PWM pulse.
9.7 AS5245 Differences to AS5045
All parameters are according to AS5045 data sheet except for the parameters shown below:
Table 15. Difference Between AS5245 and AS5045
Building Block
AS5245
AS5045
12bits, 0.088º/step.
12bits, 0.088º/step.
-40ºC to +150ºC
-40ºC to +125ºC
Data length
read: 18bits
(12bits data + 6 bits status)
OTP write: 18 bits
(12bits zero position + 6 bits mode selection)
read: 18bits
(12bits data + 6 bits status)
OTP write: 18 bits
(12bits zero position + 6 bits mode selection)
Pins 1 and 2
MagINCn, MagDECn: same feature as AS5045,
additional OTP option for red-yellow-green magnetic
range
MagINCn, MagDECn
Resolution
Ambient temperature range
Incremental encoder
Not used
Pin3 (DTest1_A); Pin 4 (DTest2_B); Pin 6 (Mode_Index)
Pin 3: not used
2x1024 ppr (12-bit)
Pin 4:not used
2x256 ppr low-jitter (10-bit)
Pin 6
MODE_Index pin selects fast or slow mode in the
default configuration. In case of incremental mode, the MODE_Index pin selects fast or slow mode in the
fast mode is selected and the pin is configured as
default configuration.
output.
Pin 12
PWM output: frequency selectable by OTP:
1µs / step, 4096 steps per revolution, f=244Hz 2µs/
step, 4096 steps per revolution, f=122Hz
PWM output: frequency selectable by OTP:
1µs / step, 4096 steps per revolution, f=244Hz
2µs/ step, 4096 steps per revolution, f=122Hz
selectable by MODE input pin:
2.5kHz, 10,4kHz
selectable by MODE input pin:
2.5kHz, 10,4kHz
384µs (slow mode)
384µs (slow mode)
96µs (fast mode)
96µs (fast mode)
Sampling frequency
Propagation delay
Transition noise
(rms; 1sigma)
OTP programming options
0.03 degrees maximum (slow mode)
0.03 degrees maximum (slow mode)
0.06 degrees maximum (fast mode)
0.06 degrees maximum (fast mode)
PPTRIM; programming voltage 3.3V – 3.6V <70ºC;
3.5V – 3.6V >70ºC;
52-bit serial data protocol; CSn, PDIO and CLK
EasyZap; programming voltage 7.3V – 7.5V; Csn;
Prog and CLK; 16-bit (32-bit) serial data protocol;
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AS5245
Data Sheet - P a c k a g e D r a w i n g s a n d M a r k i n g s
10 Package Drawings and Markings
The device is available in a QFN 32 (7mm x 7mm) package.
Figure 19. Package Drawings
AYWWIZZ
AS5245
25
32
Top View
24
1
8
17
16
9
Side View
Bottom View
Table 16. Package Dimensions
Symbol
mm
Min
Typ
inch
Max
Min
Typ
D
7 BSC
0.28 BSC
E
7 BSC
0.28 BSC
Max
D1
4.18
4.28
4.38
0.165
0.169
0.172
E1
4.18
4.28
4.38
0.165
0.169
0.172
L
0.45
0.55
0.65
0.018
0.022
0.026
b
0.25
0.30
0.35
0.010
0.012
0.014
1.00
0.031
0.035
0.039
e
A
0.65 BSC
0.80
A1
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0.90
0.203 REF
0.008 REF
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Data Sheet - R e v i s i o n H i s t o r y
Revision History
Revision
Date
Owner
Description
June 08, 2007
July 24, 2008
Initial revision
Changes made to values in Table 10 - Incremental Resolution
apg
Updated min, typ, max values for tDOvalid parameter in Table 6 - Timing
Characteristics
Feb 13, 2009
July 15, 2009
1) Note added under Table 7 - Slow and Fast Mode Parameters
2) Output Md0, Md1 description updated, (see User Selectable Settings
on page 20)
rfu
1.0
Updated values in Table 6 - Timing Characteristics for the following
parameters:
- tDOvalid
- fPWM
- PWMIN
- PWMAX
July 22, 2009
mub
1.1
July 23, 2009
Updated sections Electrical Characteristics on page 7, Timing
Characteristics on page 11 and Detailed Description on page 12
according to AS5145 datasheet.
Oct 19, 2009
Deleted the following -1) ‘OTP Programming Connection’ figure
2) Physical Placement of the magnet, Magnet Placement, Simulation
Modeling
apg
1.2
Nov 05, 2009
Timing Characteristics (page 11) - Deleted the parameter ‘PWM
Frequency’ (fPWM)
1.3
Dec 04, 2009
Updated section Internal Timing Tolerance (page 28)
Note: Typos may not be explicitly mentioned under revision history.
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AS5245
Data Sheet - O r d e r i n g I n f o r m a t i o n
11 Ordering Information
The devices are available as the standard products shown in Table 17.
Table 17. Ordering Information
Ordering Code
Description
Delivery Form
Package
AS5245HQFT
12-bit fully redundant magnetic rotary encoder
Tape & Reel
QFN 32 (7mm x 7mm)
Note: All products are RoHS compliant and Pb-free.
Buy our products or get free samples online at ICdirect: http://www.austriamicrosystems.com/ICdirect
For further information and requests, please contact us mailto:[email protected]
or find your local distributor at http://www.austriamicrosystems.com/distributor
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AS5245
Data Sheet - C o p y r i g h t s
Copyrights
Copyright © 1997-2009, austriamicrosystems AG, Tobelbaderstrasse 30, 8141 Unterpremstaetten, Austria-Europe. Trademarks Registered ®.
All rights reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of
the copyright owner.
All products and companies mentioned are trademarks or registered trademarks of their respective companies.
Disclaimer
Devices sold by austriamicrosystems AG are covered by the warranty and patent indemnification provisions appearing in its Term of Sale.
austriamicrosystems AG makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding
the freedom of the described devices from patent infringement. austriamicrosystems AG reserves the right to change specifications and prices at
any time and without notice. Therefore, prior to designing this product into a system, it is necessary to check with austriamicrosystems AG for
current information. This product is intended for use in normal commercial applications. Applications requiring extended temperature range,
unusual environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equipment are
specifically not recommended without additional processing by austriamicrosystems AG for each application. For shipments of less than 100
parts the manufacturing flow might show deviations from the standard production flow, such as test flow or test location.
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Contact Information
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Tobelbaderstrasse 30
A-8141 Unterpremstaetten, Austria
Tel: +43 (0) 3136 500 0
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