Rev. n/c
Page 1/11
Feb 2001
Key Features
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Up to 64 positions within 360
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Non contact switching
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Simple magnet as rotary encoder
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Zero position programmable (independent of
magnet orientation)
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Synchronous Serial Interface (SSI)
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Cascading is possible
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Chip Select Input
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Small 8-Pin SOIC (SMT) Package
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Temperature Range: -40
C ...+85
C
General Description
The device provides the absolute angular position of a simple magnet that is placed under or
above the device's surface. The device includes the Hall Sensor Array, signal conditioning and
post processing needed to generate a 6-bit binary code. The binary code can be easily
accessed by a Synchronous Serial Interface (SSI). The angle between the device and the
magnetic polarisation axis is exactly represented by one of 64 sectors (of 5.625
each) in the
full 360
range. Zero-Position Programming allows one time programming of a specific zero
position between the device and the magnet. The initial zero position is shown below.
6-BIT MAGNETIC
ANGULAR POSITION ENCODER
WITH SERIAL INTERFACE
S
N
4mm
0... initial
32
16
48
8
24
40
56
4
12
20
28
36
44
52
60
Ordering Information
Part Number Package
AS5020
SOIC 8
AS5020T
SOIC8 Tape and Reel
Functional Block Diagram
6-Bit Magnetic Position Encoder
Data Sheet Rev.1.0
AS5020
Rev. n/c
Page 2/11
Feb 2001
Pin Description
Pin #
Symbol
Type
Description
1
DATA
DO
DATA Output of the SSI.
If PD/CS=0, the measured angle data (6bit value) is serially
shifted out over this pin by the CLK, starting with the MSB. A
NVR Bit and a Parity bit are added. (NVR=1 indicates a Non-
Valid Range of the magnetic field.) Even Parity is given.
2
V
DD
AI
Positive Supply Voltage.
3
V
SS
AI
Negative Supply Voltage (GND).
4
PROG
DI
PROGramming Input.
This pin is used to program the zero position into a non-volatile
memory (OTP). The programmed value is subtracted from the
actual measured angle.
5
N.C.
AI
Not Connected during operation. This pin is used for testing
purposes.
6
N.C.
AI
Not Connected during operation. This pin is used for testing
purposes.
7
PD/CS
DI
Power Down Input, Disable or Chip Select (active low).
PD/CS=0 activates the device and enables the measurement.
PD/CS=1 sets the device in power save mode and puts the
DATA pin in high impedance (highZ) state.
8
CLK
DI
CLOCK Input of the SSI.
This pin is used to serially clock out the measured angle data at
Pin 7 (DATA).
DI: Digital Input
AI:
Analogue Input
DO: Digital Output
OTP: One Time Programmable
MSB: Most Significant Bit
LSB: Least Significant Bit
Note: The pins 5 and 6 must not be connected!
Pin Configuration
DATA
CLK
VDD
PD/CS
VSS
N.C.
PROG
N.C.
6-Bit Magnetic Position Encoder
Data Sheet Rev.1.0
AS5020
Rev. n/c
Page 3/11
Feb 2001
Functional Description
Measurement Principle
A hall sensor array is used to convert the magnetic field distribution above the chip surface into
a binary code.
Measurement is enabled by PD/CS=0. After each measurement a 6-bit value is latched, with
the first falling edge of the CLK, into an output shift register.
The measured data is accessible via a Synchronous Serial Interface (SSI) by any
Controller
System.
Ratiometric measurement techniques together with hall sensor conditioning circuitry allow
robust tolerance to magnet misalignment.
Permanent Encoder Magnet
A simple two-pole magnet, e.g. a standard cylindrical permanent magnet that is diametric
magnetised, is needed.
Magnetic Field strength of at least
30mTp is required at the package surface.
Standard magnet materials like rare earth AlNiCo / SmCo5 or NdFeB are recommended.
Please enquire for distributor references.
30
3mm
180
360
B/mT
/
-30
N
S
N
S
6-Bit Magnetic Position Encoder
Data Sheet Rev.1.0
AS5020
Rev. n/c
Page 4/11
Feb 2001
Measurement Modes
Two measurement modes can be selected by programming:
1) Single Read Out Mode (default)
2) Continuous Read Out Mode (OTP option)
Chip Select must be active low (PD/CS=0) to enable measurement and bring the output DATA
out of high impedance state.
After a minimum measurement period, the first falling edge of CLK latches the actual measured
angular value. The following rising edges shift the data bits out of the DATA pin, beginning with
the most significant bit. An NVR bit and even parity bit are added to the 6 bit angular value. The
NVR bit indicates a non-valid range given by bad magnet positioning.
PD/CS
CLK
DATA
D5
(MSB)
D5
(MSB)
D4
D0
NVR
Parity
Latch
actual value
Next
value
1
2
7
8
9
Reset not necessary in
Continuos Mode
Figure 1 SSI read out
In Single Read Out Mode the start of a new measurement has to be initiated with a short pulse
at PD/CS of at least 1 clockcycle. The following falling edge of CLK latches a new measured
value.
If the OTP option Continuous Read Out Mode is chosen, repeated angle measurement is
enabled by PD/CS=0. After each read out sequence the output shift register is automatically
refreshed. Fast transmission of the angular data can be performed without pulsing PD/CS.
Daisy Chain Configuration
In Singe Read Out mode, cascading allows Daisy Chain structures to minimise the
interconnection lines. Connecting DATA with PROG of the cascaded Sensor (see Fig. 2) allows
the read out of n sensors with the use of only three wires. The measurement data is shifted in
this configuration through the devices
After n x 9 clock cycles each value of n sensors is visible at pin DATA of the first sensor device.
A new measurement can be started with the falling edge of CLK after a power down pulse at
PD/CS.
AS5020
PROG DATA
CLK PD/CS
AS5020
PROG DATA
CLK PD/CS
AS5020
PROG DATA
CLK PD/CS
C
CLK
Power Down
Data In
n
1
2
Figure 2 Typical Daisy Chain Configuration
6-Bit Magnetic Position Encoder
Data Sheet Rev.1.0
AS5020
Rev. n/c
Page 5/11
Feb 2001
PD/CS
CLK
DATA
D4
D0
Latch
actual value
Next
value
1
2
7
8
9
D5
NVR
Parity
D5
D4 D0
NVR
Parity
D5
angle 1
angle 2
angle n
Figure 3 Daisy Chain read out
Zero Position Programming
A simple single pin programming allows changing the initial zero position. It is easy to program
permanently a new zero-reference into the internal OTP (one time programmable) ROM. This
allows a fast and economic magnet placement since the intrinsic orientation is not important.
Single Pin Programming is provided via the PROG pin. Fig.4 shows the typical programming
sequence needed for fixing the new zero position.
Zero Position Programming Sequence
Before calibration, the new zero position must be adjusted in measurement mode (PD/CS=0).
The rising edge of PD/CS gets the actual position and stores it internally for the permanent
programming. A high level at the PROG Pin during power-down (PD/CS=1) with a minimum
duration of 300
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s
select the latched position information and zap the reference value into the OTP ROM.
Continuous Read Out Mode Selection
An optional 9
th
pulse after the initialisation pulse, the dummy pulse, and the 6 data pulses can
be used to set Continuous Read Out Mode (see Fig.4).
PROG [V]
8
0
t
Initialisation
Zero Position Programming
1
2
3
4
Bit 0
Bit 1
Bit 3
Bit 2
Bit 5
Bit 4
5
6
7
8
Optional
Cont.
Mode
Dummy
Calibration Position
Latched
Measurement
Enable
CS
Enable
Programming
t
ProgEN
Figure 4 Programming sequence
Note: Daisy Chain configuration is not possible in Continuous Read Out Mode.
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