Revision December 2002

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Key Features

Rotary absolute position measurement with 6-bit

resolution

64 positions within full 360° degree rotation range

Rotation speed of magnetic source up to 30,000 rpm

Digital output signal with Synchronous Serial Interface

(SSI)

Wide temperature range: - 40° C to +125° C

(-40° F to +257° F)

Low power dissipation: less than 5ľ W per sample

System on Chip: Hall effect sensors and signal processing

combined on a single chip

Simple permanent magnetic source required

Benefits

Non-contact switching providing high reliability and

long mechanical life time. Ideal for electrically isolated

applications.

Extremely compact SOIC-8 package

Ease of implementation with reduced number of external

components

User specific zero position programmable into internal

OTP

Multiple sensors connected in daisy chain mode through

simple 3 wire connection

Flexibility for different operation modes

No calibration needed

Extremely tolerant to magnetic and harsh environment

Tolerant to magnetic source misalignment

Applications

Motion control

Precision linear- or angular position sensing

Precision angular encoding

Software re-configurable rotary switch

Isolated rotary switch for safety critical applications

Alternative to potentiometers

General Description

The AS5020 device provides the absolute angular position

encoding of a simple magnet source that is placed at the

device's surface. A total of 64 absolute angular positions are

available within the full range of 360° (typical sector size:

5.625° ).

Figure 1

Placement of AS5020 device and magnet source

The device includes a Hall sensor array, the signal

conditioning and the post processing needed to generate a 6-

bit binary code. The binary code may be accessed via the

Synchronous Serial Interface (SSI).

Zero-position programming allows one time programming of a

user specific zero position between the device and the magnet

source.

6bit

ADC

Measurement

Adder & Output-

OTP-ROM

Zero-Position

Programming

Power down, Reset

Sensor-Array

VDD

PROG

GND

CLK

DATA

PD/CSn

Figure 2

Block diagram

DATA SHEET

AS5020

6-BIT ABSOLUTE ANGULAR POSITION ENCODER

DATA SHEET

AS5020-E

6-BIT ABSOLUTE ANGULAR POSITION ENCODER

(Extended Temperature Range)

DATA SHEET

AS5020: 6-BIT ABSOLUTE ANGULAR POSITION ENCODER

Revision December 2002

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Pin Configuration

CLK

DATA

N.C.

PD/CSn

PROG

VSS

VDD

Pin Description

Pin #

Symbol

Type

Description

DATA

DATA Output of the SSI.
If PD/CSn=0, the measured angle data
(6-bit value) is serially shifted out over
this pin by the CLK, starting with the
MSB. A NVR bit and a PARITY bit are
added. Even Parity is given.
(NVR=1 indicates a Non Valid Range
of the magnetic field)

Positive Supply Voltage.

S S

Negative Supply Voltage (GND).

PROG

PROGramming Input
This pin is used to program the zero
position into a non-volatile memory
(One Time Programmable). The
programmed value is subtracted from
the actual measured angle.
(This pin is also used for Data In
during Daisy-Chain function)

N.C.

Not Connected during operation. This
pin is for manufacturers use only

N.C.

Not Connected during operation. This
pin is for manufacturers use only.

PD/CSn

Power Down Input, Disable or Chip
Select (active low).
PD/CSn=0 activates the device and
enables the measurement.
PD/CSn=1 sets the device in power
save mode and puts the DATA pin in
high impedance (high Z) state.

CLK

CLOCK Input of the SSI.
Pin 8 serially clocks out the measured
angle data at Pin 1 (DATA).

DI:

Digital Input

AI:

Analogue Input

DO:

Digital Output

MSB:

Most Significant Bit

Note:

Pins 5 and 6 may be either left open or
connected together

Functional Description

A Hall sensor array is used to convert the magnetic field

distributed above the chip surface into a binary code. That

represents the absolute angular position of the magnetic field

with respect to the device.

The measured data is accessible via a Synchronous Serial
Interface (SSI) by means of any micro-controller system.

The AS5020 is extremely tolerant of magnetic misalignment

and of environmental influences due to the design adopted for

the ratiometric measurement and Hall sensor conditioning

circuitry.

Due to the very high level of system integration the AS5020

allows easy implementation of an angular measuring system.

The AS5020 requires only two external components, a

magnetic field source and a de-coupling capacitor.

As illustrated in figure 3, a simple two-pole permanent magnet

may be used as the magnetic field source.

The magnet may be a diametrically magnetized, cylindrical

standard magnet. Magnetic materials such as rare earth

AlNiCo / SmCo5 or NdFeB are recommended. Typically the

magnet size should be 3 to 6mm in diameter and 2 to 3mm in

height. The typical distance between the magnet and the

device is 0.5 to 1.5mm.

A magnetic field strength of typically

ą40mT is required at the

package surface and a diameter of 1.6mm.

3 - 6mm

-40

180°

360°

/ °

B/mT

Figure 3

Typical magnet and magnetic field at the radius of 3mm

AS5020: 6-BIT ABSOLUTE ANGULAR POSITION ENCODER

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Functional Description of the

Measurement Cycle and Data Output

See figure 4

Chip Select must be active low (PD/CSn=0) to enable

measurement and to bring the output DATA from high

impedance to logic low.

After a minimum measurement period, the first falling edge of

CLK latches the current measured angular information of the

applied magnetic field. The following rising edges of CLK shift

the data out at DATA as the following 8-bit serial word:

Bits D<5:0> represent the measured angular data. The most

significant bit is clocked out first.

NVR = 1 indicates a Non Valid Range of the magnetic field.

The PARITY bit provides integrity information about the serial

word.

With Chip Select at logic high, the device returns to the power

down state.

Programming of Continuous Read Out Mode and user specific

zero position are described in more detail below.

Device Operating Modes

Single Measurement Mode is the default mode.

Continuous Read Out Mode and the user specific Zero

Position may be programmed with a single pin programming at

the DATA pin. This programming is permanently stored into

the internal OTP ROM (One Time Programmable).

Single Measurement Mode and

Daisy Chain Mode

This is the default mode and allows read out for the angular

position of the magnetic source as shown in figure 4.

1.1

PD/CSn must be taken logic low. DATA will then switch from

high impedance to logic low and the measurement will be

initiated.

1.2

After the minimum measurement time, data will be internally

latched at the falling edge of CLK.

1.3

After the rising edge of CLK the DATA is valid

1.4

The serial word readout sequence is D<5:0>, NVR and

PARITY.

1.5

The next measurement is initiated with an active high pulse at

PD/CSn with duration t

reset

1.6

During steps 1.4 and 1.5, while data is clocked out at DATA,

the data at PROG is clocked into the device. Further clock

pulses applied to CLK will serially clock this data out at DATA.

This function allows implementation of the daisy chain function.

Continuous Read Out Mode

Continuous Read Out Mode needs to be programmed via PROG pin

and allows continuous high speed measurement as shown in figure 5.

The measured data will be internally latched and may be read if

requested.

2.1

The falling edge of CLK synchronizes the DATA. Due to

internal anti-collision of the value update the last completely

measured value will be taken.

2.2

An external clock applied to CLK will shift the data from the

output register of the device. The rising edge of the clock will

latch the data to the output register. The 8 data bits may then

be latched into an external micro-controller with the falling

edges of the clock.

2.3

The serial word readout sequence is D<5:0>, NVR and

PARITY.

2.4

After each readout sequence the output shift register is

automatically refreshed at the falling edge of the ninth clock

cycle

Note: Daisy Chain Configuration is not possible in this mode.

Programming of Zero Position and

Continuous Read Out Mode

The possibility to program the user specific zero position gives

many advantages (e.g. it simplifies the assembly at the

production line, as the orientation of the magnet does not

need to be considered. It also allows the design of software

programmable rotary switches).

The initial zero position is shown in figure 7.

AS5020: 6-BIT ABSOLUTE ANGULAR POSITION ENCODER

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Timing Diagrams

NVR

PARITY

setup

reset

meas

latch

CLK

CLK_DATA

DATA

PD/CSn

CLK

VDD

Figure 4

Timing diagram in Single Read Out mode

NVR

PARITY

setup

DATA

CLK

VDD

PD/CSn

Figure 5

Timing diagram in Continuous Read Out mode

Dummy

Enable

Programming

PROG

Initialization

wait

Zero Position Programming

Optional

Continuous

Read Out Mode

Bit0

Bit5

Bit4

Bit3

Bit2

Bit1

Measurement

Enable

CSn

Calibration Position

Latched

ProgEN

Zap

Prog

Figure 6

Programming sequence

AS5020: 6-BIT ABSOLUTE ANGULAR POSITION ENCODER

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4mm

Figure 7

Initial angular orientation

Before programming the user specific zero position and

Continuous Read Out Mode, the magnet must be adjusted in

measurement mode (PD/CSn=0).

As shown in figure 6, the rising edge of PD/CSn measures

the actual position and stores it internally for the permanent

programming. PD/CS must be high during the whole

programming sequence.

The first 8V pulse after the minimum waiting time t

wa it

sets

the device into programming mode. It is important that this

first pulse has a minimum duration of t

p rog E N

= 200 ľ s. A chip

response pulse at pin DATA confirms that the chip is in

programming mode.

The following 7 pulses with 8V/5

ľs select the latched

position information and permanently write the reference

value into the OTP ROM.

An optional 9th pulse can be used to program the device to

Continuous Read Out Mode.

Low Power Application

In low power applications the power down current of 500ľ A

may be too high, in such a case the AS5020 needs to be

completely switched off.

Due to the AS5020´s capability of high speed measurement,

a storage capacitor may be used to store the energy for the

fast measurement and read out cycle of a minimum of 33ľ s.

The sensor may then be completely switched off (S1 FET) if

no position information is required. During this time the

storage capacitor is recharged.

PROG

PD/CSn

VDD

GND

CLK

DataOut

FET BS170

Buffer

Limit

+5V

AS5020

Continuous

Output Mode

Limit

= 1k

Buffer

= 2,2 - 10ľF

Figure 8

Schematics for basic low power application

At power on, after a minimum setup time of 20ľ s and a

minimum latch time of 5ľ s the data may be clocked out with

the maximum frequency within the supply voltage range of

4.5 to 5.5V. A supply voltage drop is allowed (see figure 9)

In one measurement cycle, multiple readings in Continuous

Output Mode may be performed to improve the safety.

Setup

Latch

CLK

Min. 20ľs 5ľs 1ľs

VDD = 5V
+/-10 %

VDD

CLK

DataOut

D0 NVR

Parity

Figure 9

Timing diagram for low power application

Part Number AS5020-E