AS5040-ASSU - Austriamicrosystems

www.austriamicrosystems.com Revision 2.10 1 - 33

1 General Description

The AS5040 is a contactless magnetic rotary encoder

for accurate angular measurement over a full turn of

360°. It is a system-on-chip, combining integrated Hall

elements, analog front end and digital signal processing

in a single device.

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.

The absolute angle measurement provides instant

indication of the magnet’s angular position with a

resolution of 0.35° = 1024 positions per revolution. This

digital data is available as a serial bit stream and as a

PWM signal.

Furthermore, a user-programmable incremental output

is available, making the chip suitable for replacement of

various optical encoders.

An internal voltage regulator allows the AS5040 to

operate at either 3.3 V or 5 V supplies.

Figure 1: Typical Arrangement of AS5040 and Magnet

Benefits

 Complete system-on-chip

 Flexible system solution provides absolute,

PWM and incremental outputs simultaneously

 Ideal for applications in harsh environments

due to contactless position sensing

 Tolerant to magnet misalignment and airgap

variations

 No temperature compensation necessary

 No calibration required

2 Key Features

 Contactless high resolution rotational position

encoding over a full turn of 360 degrees

 Two digital 10bit absolute outputs:

- Serial interface and

- Pulse width modulated (PWM) output

 Three incremental output modes:

- Quadrature A/B and Index output signal

- Step / Direction and Index output signal

- 3-phase commutation for brushless DC

motors

- 10, 9, 8 or 7 bit user programmable

resolution

 User programmable zero / index position

 Failure detection mode for magnet placement

monitoring and loss of power supply

 Rotational speeds up to 30,000 rpm

 Push button functionality detects movement

of magnet in Z-axis

 Serial read-out of multiple interconnected

AS5040 devices using Daisy Chain mode

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

 Fully automotive qualified to AEC-Q100,

grade 1

 Small Pb-free package: SSOP 16 (5.3mm x

6.2mm)

3 Applications

 Industrial applications:

- Contactless rotary position sensing

- Robotics

- Brushless DC motor commutation

- Power tools

 Automotive applications:

- Steering wheel position sensing

- Gas pedal position sensing

- Transmission gearbox encoder

- Headlight position control

- Power seat position indicator

 Office equipment: printers, scanners, copiers

 Replacement of optical encoders

 Front panel rotary switches

 Replacement of potentiometers

AS5040

10Bit 360° Programmable Magnetic Rotary Encoder

Data Sheet

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 2 - 33

4 Pin Configuration

Figure 2: Pin Configuration SSOP16

161

MagINCn

MagDECn

A_LSB_U

B_Dir_V

Index_W

VSS

Prog DO

CLK

CSn

PWM_LSB

VDD3V3

VDD5V

AS5040

Pin Description

Table 2 shows the description of each pin of the standard SSOP16 package (Shrink Small Outline Package, 16 leads,

body size: 5.3mm x 6.2mmm; see Figure 2).

Pins 7, 15 and 16 are supply pins, pins 5, 13 and 14 are for internal use and must not be connected.

Pins 1 and 2 are the magnetic field change indicators, MagINCn and MagDECn (magnetic field strength increase or

decrease through variation of the distance between the magnet and the device). These outputs can be used to detect

the valid magnetic field range. Furthermore those indicators can also be used for contact-less push-button

functionality.

Pins 3, 4 and 6 are the incremental pulse output pins. The functionality of these pins can be configured through

programming the one-time programmable (OTP) register.

Table 1: Pin Assignment for the Dif ferent Incremental Output Modes

Output Mode Pin 3 Pin 4 Pin 6 Pin 12

1.x: quadrature A B Index PWM

2.x:step/direction LSB Direction Index PWM

3.x: commutation U V W LSB

Mode 1.x: Quadrature A/B Output

Represents the default quadrature A/B signal mode.

Mode 2.x: Step / Direction Output

Configures pin 3 to deliver up to 512 pulses (up to 1024 state changes) per revolution. It is equivalent to the LSB

(least significant bit) of the absolute position value. Pin 4 provides the information of the rotational direction.

Both modes (mode 1.x and mode 2.x) provide an index signal (1 pulse/revolution) with an adjustable width of one LSB

or three LSB’s.

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 3 - 33

Table 2 Pin Description SSOP16

Pin Symbol Type Description

1 MagINCn DO_OD

Magnet Field Magnitude INCrease; active low, indicates a distance

reduction between the magnet and the device surface.

2 MagDECn DO_OD

Magnet Field Magnitude DECrease; active low, indicates a distance

increase between the device and the magnet.

A_LSB_U DO

Mode1.x: Quadrature A channel

Mode2.x: Least Significant Bit

Mode3.x: U signal (phase1)

B_Dir_V DO

Mode1.x: Quadrature B channel quarter period shift to channel A.

Mode2.x: Direction of Rotation

Mode3.x: V signal (phase2)

5 NC - Must be left unconnected

6 Index_W DO

Mode1.x and Mode2.x : Index signal indicates the absolute zero position

Mode3.x: W signal (phase3)

7 VSS S Negative Supply Voltage (GND)

Prog DI_PD

OTP Programming Input and Data Input for Daisy Chain mode. Internal

pull-down resistor (~74kΩ).

May be connected to VSS if programming is not used

9 DO DO_T

Data Output of Synchronous Serial Interface

10 CLK DI, ST

Clock Input of Synchronous Serial Interface; Schmitt-Trigger input

11 CSn DI_PU, ST

Chip Select, active low; Schmitt-Trigger input, internal pull-up resistor

(~50kΩ) connect to VSS in incremental mode (see 0)

12 PWM_LSB DO

Pulse Width Modulation of approx. 1kHz; LSB in Mode3.x

13 NC - Must be left unconnected

14 NC - Must be left unconnected

15 VDD3V3 S 3V-Regulator Output (see Figure 19)

16 VDD5V S Positive Supply Voltage 5 V

DO_OD digital output open drain S supply pin

DO digital output DI digital input

DI_PD digital input pull-down DO_T digital output /tri-state

DI_PU digital input pull-up ST Schmitt-Trigger input

Mode 3.x: Brushless DC Motor Commutation Mode

In addition to the absolute encoder output over the SSI interface, this mode provides commutation signals for

brushless DC motors with either one pole pair or two pole pair rotors. The commutation signals are usually provided

by 3 discrete Hall switches, which are no longer required, as the AS5040 can fulfill two tasks in parallel: absolute

encoder + BLDC motor commutation.

In this mode, pin 12 provides the LSB output instead of the PWM (Pulse-Width-Modulation) signal.

Pin 8 (Prog) is also used to program the different incremental interface modes, the incremental resolution and the

zero position into the OTP (see page 18).

This pin is also used as digital input to shift serial data through the device in Daisy Chain configuration,

(see page 11).

Pin 11 Chip Select (CSn; active low) selects a device within a network of AS5040 encoders and initiates serial data

transfer. A logic high at CSn puts the data output pin (DO) to tri-state and terminates serial data transfer. This pin is

also used for alignment mode (page 21) and programming mode (page 16).

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 4 - 33

Pin 12 allows a single wire output of the 10-bit absolute position value. The value is encoded into a pulse width

modulated signal with 1µs pulse width per step (1µs to 1024µs over a full turn). By using an external low pass filter,

the digital PWM signal is converted into an analog voltage, allowing a direct replacement of potentiometers.

5 Electrical Characteristics

Absolute Max i mum Rati ngs (non operating)

Stresses beyond those listed under “Absolute Maximum Ratings“ may cause permanent damage to the device. These are stress

ratings only. Functional operation of the device at these or any other conditions beyond those indicated under “Operating

Conditions” is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Parameter Symbol Min Max Unit Note

DC supply voltage at pin VDD5V VDD5V -0.3 7 V

DC supply voltage at pin VDD3V3 VDD3V3 -0.3 5 V

-0.3 VDD5V +0.3 Pins MagIncn, MagDecn, CLK, CSn,

Input pin voltage Vin -0.3 7.5

V Pin Prog

Input current (latchup immunity) Iscr -100 100 mA Norm: JEDEC 78

Electrostatic discharge ESD ± 2 kV Norm: MIL 883 E method 3015

Storage temperature Tstrg -55 125 °C Min – 67°F ; Max +257°F

Body temperature (Lead-free

package) TBody 260 °C

t=20 to 40s, Norm: IPC/JEDEC J-

Std-020C

Lead finish 100% Sn “matte tin”

Humidity non-condensing H 5 85 %

Operating Conditions

Parameter Symbol Min Typ Max Unit Note

Ambient temperature Tamb -40 125 °C -40°F…+257°F

Supply current Isupp 16 21 mA

External supply voltage at pin VDD5V

Internal regulator output voltage at pin

VDD3V3

VDD5V

VDD3V3

4.5

3.0

5.0

3.3

5.5

3.6

V 5V operation

External supply voltage at pin VDD5V,

VDD3V3

VDD5V

VDD3V3

3.0

3.3

3.6

3.3V operation (pins VDD5V and

VDD3V3 connected)

DC Characteris t ics fo r D ig ital Inputs and Ou tpu ts

CMOS Schmitt-Trigger Inputs: CLK, CSn (CSn = internal Pull-up)

(operating conditions: Tamb = -40 to +125°C, VDD5V = 3.0-3.6V (3V operation) VDD5V = 4.5-5.5V (5V operation)

unless otherwise noted)

Parameter Symbol Min Max Unit Note

High level input voltage VIH 0.7 * VDD5V V Normal operation

Low level input voltage VIL 0.3 * VDD5V V

Schmitt Trigger hysteresis VIon- VIoff 1 V

-1 1 CLK only

Input leakage current

Pull-up low level input current

ILEAK

IiL -30 -100

µA

µA CSn only, VDD5V: 5.0V

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 5 - 33

CMOS / Program Input: Prog

(operating conditions: Tamb = -40 to +125°C, VDD5V = 3.0-3.6V (3V operation) VDD5V = 4.5-5.5V (5V operation)

unless otherwise noted)

Parameter Symbol Min Max Unit Note

High level input voltage VIH 0.7 * VDD5V 5 V

High level input voltage VPROG See “programming conditions” V During programming

Low level input voltage VIL 0.3 * VDD5V V

Pull-down high level input current IiL 100 µA VDD5V: 5.5V

CMOS Output Open Drain: MagINCn, MagDECn

(operating conditions: Tamb = -40 to +125°C, VDD5V = 3.0-3.6V (3V operation) VDD5V = 4.5-5.5V (5V operation)

unless otherwise noted)

Parameter Symbol Min Max Unit Note

Low level output voltage VOL VSS+0.4 V

Output current IO 4

2 mA VDD5V: 4.5V

VDD5V: 3V

Open drain leakage current IOZ 1 µA

CMOS Output: A, B, Index, PWM

(operating conditions: Tamb = -40 to +125°C, VDD5V = 3.0-3.6V (3V operation) VDD5V = 4.5-5.5V (5V operation)

unless otherwise noted)

Parameter Symbol Min Max Unit Not e

High level output voltage VOH VDD5V-0.5 V

Low level output voltage VOL VSS+0.4 V

Output current IO 4

2 mA VDD5V: 4.5V

VDD5V: 3V

Tristate CMOS Ou tput: DO

(operating conditions: Tamb = -40 to +125°C, VDD5V = 3.0-3.6V (3V operation) VDD5V = 4.5-5.5V (5V operation)

unless otherwise noted)

Parameter Symbol Min Max Unit Not e

High level output voltage VOH VDD5V –0.5 V

Low level output voltage VOL VSS+0.4 V

Output current IO 4

2 mA VDD5V: 4.5V

VDD5V: 3V

Tri-state leakage current IOZ 1 µA

Magnetic Input Specification

(operating conditions: Tamb = -40 to +125°C, VDD5V = 3.0-3.6V (3V operation) VDD5V = 4.5-5.5V (5V operation) unless otherwise

noted)

Two-pole cylindrical diametrically magnetised source:

Parameter Symbol Min Typ Max Unit Note

Diameter dmag 4 6 mm

Thickness tmag 2.5 mm

Recommended magnet: Ø 6mm x 2.5mm for

cylindrical magnets

Magnetic input field

amplitude Bpk 45

75 mT

Required vertical component of the

magnetic field strength on the die’s surface,

measured along a concentric circle with a

radius of 1.1mm

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 6 - 33

Parameter Symbol Min Typ Max Unit Note

Magnetic offset Boff ± 10 mT Constant magnetic stray field

Field non-linearity 5 % Including offset gradient

fmag_abs 10 Hz

Absolute mode: 600 rpm @ readout of 1024

positions (see Table 6)

Input frequency

(rotational speed of

magnet) fmag_inc

500 Hz

Incremental mode: no missing pulses at

rotational speeds of up to 30,000 rpm (see

Table 6)

0.25 Max. X-Y offset between defined IC package

center and magnet axis (see Figure 21)

Displacement radius Disp

0.485

mm Max. X-Y offset between chip center and

magnet axis.

Chip placement

tolerance

±0.23

5 mm Placement tolerance of chip within IC

package (see Figure 23)

-0.12 NdFeB (Neodymium Iron Boron)

Recommended magnet

material and

temperature drift

-0.035

%/K SmCo (Samarium Cobalt)

Electrical System Specifications

(operating conditions: Tamb = -40 to +125°C, VDD5V = 3.0-3.6V (3V operation) VDD5V = 4.5-5.5V (5V operation) unless otherwise

noted)

Parameter Symbol Min Typ Max Unit Note

Resolution RES 10 bit 0.352 deg

7 bit

8 bit

9 bit

10 bit

LSB

2.813

1.406

0.703

0.352

deg

Adjustable resolution only available

for incremental output modes;

Least significant bit, minimum step

Integral non-linearity

(optimum) INLopt ± 0.5 deg

Maximum error with respect to the

best line fit.

Verified at optimum magnet

placement, Tamb =25 °C.

Integral non-linearity

(optimum) INLtemp ± 0.9 deg

Maximum error with respect to the

best line fit.

Verified at optimum magnet

placement ,

Tamb = -40 to +125°C

Integral non-linearity INL ± 1.4 deg

Best line fit = (Errmax – Errmin) / 2

Over displacement tolerance with

6mm diameter magnet, Tamb = -40 to

+125°C

Differential non-linearity DNL ± 0.176 deg 10bit, no missing codes

Transition noise TN 0.12 Deg

RMS RMS equivalent to 1 sigma

Hysteresis Hyst 0.704 deg Incremental modes only

Power-on reset thresholds

On voltage; 300mV typ.

hysteresis

Off voltage; 300mV typ.

hysteresis

Von

Voff

1.37

1.08

2.2

1.9

2.9

2.6

V DC supply voltage 3.3V (VDD3V3)

DC supply voltage 3.3V (VDD3V3)

Power-up time tPwrUp 50 ms Until offset compensation finished

System propagation delay

absolute output tdelay 48 µs Includes delay of ADC and DSP

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 7 - 33

Parameter Symbol Min Typ Max Unit Note

System propagation delay

incremental output 192 µs Calculation over two samples

9.90 10.42 10.94 Internal sampling rate, Tamb = 25°C

Sampling rate for absolute

output fS 9.38 10.42 11.46

kHz Internal sampling rate, Tamb = -40 to

+125°C

Read-out frequency CLK 1 MHz

Max. clock frequency to read out

serial data

Figure 3: Integral and Differential Non-linearity Example (exaggerated curve)

80° 360 °

0°

512

1023

α10bit code

0.35°INL

Ideal c urv e

Actual curve

512

1023

DNL+1LSB

[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.

Timing Characteristics

Synchronous Serial Interface (SSI)

(operating conditions: Tamb = -40 to +125°C, VDD5V = 3.0-3.6V (3V operation) VDD5V = 4.5-5.5V (5V operation) unless otherwise

noted)

Parameter Symbol Min Typ Max Unit Note

Data output activated

(logic high) t DO active 100 ns

Time between falling edge of CSn and

data output activated

First data shifted to output

Time between falling edge of CSn and

first falling edge of CLK

Start of data output T CLK / 2 500 ns

Rising edge of CLK shifts out one bit at a

time

Data output valid t DO valid 357 413 ns

Time between rising edge of CLK and

data output valid

Data output tristate t DO tristate 100 ns

After the last bit DO changes back to

“tristate”

Pulse width of CSn t CSn 500 ns

CSn = high; To initiate read-out of next

angular position

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 8 - 33

Parameter Symbol Min Typ Max Unit Note

Read-out frequency fCLK >0 1 MHz Clock frequency to read out serial data

Pulse Width Modulation Output

(operating conditions: Tamb = -40 to +125°C, VDD5V = 3.0-3.6V (3V operation) VDD5V = 4.5-5.5V (5V operation) unless otherwise

noted)

Parameter Symbol Min Typ Max Unit Note

0.927 0.976 1.024 Signal period = 1025µs ±5% at Tamb = 25°C

PWM frequency f PWM 0.878 0.976 1.074 KHz

=1025µs ±10% at Tamb = -40 to +125°C

Minimum pulse width PW MIN 0.90 1 1.10 µs Position 0d; angle 0 degree

Maximum pulse width PW MAX 922 1024 1126 µs Position 1023d; angle 359.65 degree

Incremental Outputs

(operating conditions: Tamb = -40 to +125°C, VDD5V = 3.0-3.6V (3V operation) VDD5V = 4.5-5.5V (5V operation) unless otherwise

noted)

Parameter Symbol Min Typ Max Unit Not e

Incremental outputs valid

after power-up

t Incremental

outputs valid 500 ns

Time between first falling edge of CSn

after power-up and valid incremental

outputs

Directional indication valid t Dir valid 500 ns

Time between rising or falling edge of

LSB output and valid directional indication

Programming Conditions

(operating conditions: Tamb = -40 to +125°C, VDD5V = 3.0-3.6V (3V operation) VDD5V = 4.5-5.5V (5V operation) unless otherwise

noted)

Parameter Symbol Min Typ Max Unit Note

Programming enable time t Prog enable 2 µs

Time between rising edge at Prog pin

and rising edge of CSn

Write data start t Data in 2 µs

Write data valid t Data in valid 250 ns

Write data at the rising edge of

CLKPROG

Load programming data t Load PROG 3 µs

Rise time of VPROG before

CLKPROG t PrgR 0 µs

Hold time of VPROG after

CLKPROG t PrgH 0 5 µs

Write data – programming

CLKPROG CLK PROG 250 kHz

CLK pulse width t PROG 1.8 2 2.2 µs During programming; 16 clock cycles

Hold time of Vprog after

programming t PROG finished 2 µs

Programmed data is available after

next power-on

Programming voltage V PROG 7.3 7.4 7.5 V Must be switched off after zapping

Programming voltage off level V ProgOff 0 1 V Line must be discharged to this level

Programming current I PROG 130 mA During programming

Analog read CLK CLKAread 100 kHz Analog readback mode

Programmed zener voltage

(log.1) Vprogrammed 100 mV

Unprogrammed zener voltage

(log. 0) Vunprogrammed 1 V

VRef-VPROG during analog readback

mode (see Analog Readback Mode)

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 9 - 33

6 Functional Description

The AS5040 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 AS5040

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 Ma gI NCn and MagDE C n 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 20).

The AS5040 senses the orientation of the magnetic field and calculates a 10-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).

Besides the absolute angular position information the device simultaneously provides incremental output signals. The

various incremental output modes can be selected by programming the OTP mode register bits (see page 19). As

long as no programming voltage is applied to pin Prog, the new setting may be overwritten at any time and will be

reset to default when power is turned off. To make the setting permanent, the OTP register must be programmed (see

Figure 15). The default setting is a quadrature A/B mode including the Index signal with a pulse width of 1 LSB. The

Index signal is logic high at the user programmable zero position.

The AS5040 is tolerant to magnet misalignment and magnetic stray fields due to differential measurement technique

and Hall sensor conditioning circuitry.

Figure 4: AS5040 Block Diagram

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 10 - 33

7 10-bit Absolute Angular Position Output

Synchronous Serial Interface (SSI)

Figure 5: Synchronous Serial Interface with Absolute Angular Position Data

Even

PAR

CSn

CLK

DO D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

18 16

COF LINOCF Mag

INC Mag

DEC

t DO active t DO Tristate

t CLK FE

t DO valid

t CLK FE

t CSn T CLK / 2

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 16 bits, the first 10 bits are the angular information D[9:0], 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 log. “high” pulse at CSn with a minimum duration of tCSn.

Data Content:

D9:D0 absolute angular position data (MSB is clocked out first)

OCF (Offset Compensation Finished), logic high indicates the finished Offset Compensation Algorithm.

For fast startup, this bit may be polled by the external microcontroller. As soon as this bit is set, the AS5040 has

completed the startup and the data is valid (see Table 4)

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.

MagINCn, (Magnitude Increase) becomes HIGH, when the magnet is pushed towards the IC, thus the magnetic field

strength is increasing.

MagDECn, (Magnitude Decrease) becomes HIGH, when the magnet is pulled away from the IC, thus the magnetic

field strength is decreasing.

Both signals HIGH indicate a magnetic field that is out of the allowed range (see Table 3).

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 11 - 33

Table 3: Magnetic Magnitude Variation Indicator

Mag

INCn Mag

DECn Description

0 0 No distance change; Magnetic input field OK (in range, 45..75mT)

0 1

Distance increase: Pull-function. This state is dynamic, it is only active while the magnet is

moving away from the chip in Z-axis

1 0

Distance decrease: Push- function. This state is dynamic, it is only active while the magnet is

moving towards the chip in Z.-axis.

1 1 Magnetic Input Field invalid – out of range: <45mT or >75mT (or missing magnet)

Note: Pins 1 and 2 (MagINCn, MagDECn) are open drain outputs and require external pull-up resistors. 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 3).

Even Parity bit for transmission error detection of bits 1…15 (D9…D0, OCF, COF, LIN, MagINCn, MagDECn)

The absolute angular output is always set to a resolution of 10 bit. Placing the magnet above the chip, angular values

increase in clockwise direction by default.

Data D9:D0 is valid, when the status bits have the following configurations:

Table 4: Status Bit Outputs

OCF COF LIN Mag

INCn Mag

DECn Parity

0 0

0 1

1 0 0

1 0

even checksum of bits

1:15

The absolute angular position is sampled at a rate of 10kHz (0.1ms). This allows reading of all 1024 positions per 360

degrees within 0.1 seconds = 9.76Hz (~10Hz) without skipping any position. Multiplying 10Hz by 60, results the

corresponding maximum rotational speed of 600 rpm.

Readout of every second angular position allows for rotational speeds of up to 1200rpm.

Consequently, increasing the rotational speed reduces the number of absolute angular positions per revolution (see

Table 7). Regardless of the rotational speed or the number of positions to be read out, the absolute angular value is

always given at the highest resolution of 10 bit.

The incremental outputs are not affected by rotational speed restrictions due to the implemented interpolator. The

incremental output signals may be used for high-speed applications with rotational speeds of up to 30,000 rpm without

missing pulses.

Daisy Chain Mode

The Daisy Chain mode allows connection of several AS5040’s in series, while still keeping just one digital input for

data transfer (see “Data IN” in Figure 6 below). This mode is accomplished by connecting the data output (DO; pin 9)

to the data input (Prog; pin 8) of the subsequent device. An RC filter must be implemented between each PROG pin

of device n and DO pin of device n+1, to prevent the encoders to enter the alignment mode, in case of ESD

discharge, long cables, or not conform signal levels or shape. Using the values R=100R and C=1nF allow a max. CLK

frequency of 1MHz on the whole chain. The serial data of all connected devices is read from the DO pin of the first

device in the chain. The Prog pin of the last device in the chain should be connected to VSS. The length of the serial

bit stream increases with every connected device, it is

n * (16+1) bits:

e.g. 34 bit for two devices, 51 bit for three devices, etc…

The last data bit of the first device (Parity) is followed by a logic low bit and the first data bit of the second device (D9),

etc… (see Figure 7).

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 12 - 33

Programming Daisy Chained Devices

In Daisy Chain mode, the Prog pin is connected directly to the DO pin of the subsequent device in the chain (see

Figure 6). During programming (see section 12), a programming voltage of 7.5V must be applied to pin Prog. This

voltage level exceeds the limits for pin DO, so one of the following precautions must be made during programming:

 open the connection DOÆProg during programming or

 add a Schottky diode between DO and Prog (Anode = DO, Cathode = Prog)

Due to the parallel connection of CLK and CSn, all connected devices may be programmed simultaneously.

Figure 6: Daisy Chain Hardware Configuration

CSn

PROG

CLK

CSn

CLK

CSn

CLK

PROG

CSn

CLK

PROG

100R 100R

1nF 1nF

GND GND GND

MCU AS5040 AS5040 AS5040

Figure 7: Daisy Chain Mode Data Transfer

Even

PAR

CSn

CLK

DO D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

18 16

COF LINOCF Mag

INC Mag

DEC

tCLK FE

Angular Position Data Status Bits

TCLK/2

tDO active tDO valid

D9 D8 D7

1st Device 2nd Device

Angular Position Data

8 Incremental Outputs

Three different incremental output modes are possible with quadrature A/B being the default mode.

Figure 8 shows the two-channel quadrature as well as the step / direction incremental signal (LSB) and the direction

bit in clockwise (CW) and counter-clockwise (CCW) direction.

Quadrature A/B Output (Quad A/B Mode)

The phase shift between channel A and B indicates the direction of the magnet movement. Channel A leads channel

B at a clockwise rotation of the magnet (top view) by 90 electrical degrees. Channel B leads channel A at a counter-

clockwise rotation.

LSB Output (S tep / D irec t ion Mode )

Output LSB reflects the LSB (least significant bit) of the programmed incremental resolution (OTP Register Bit Div0,

Div1). Output Dir provides information about the rotational direction of the magnet, which may be placed above or

below the device (1=clockwise; 0=counter clockwise; top view). Dir is updated with every LSB change.

In both modes (quad A/B, step/direction) the resolution and the index output are user programmable. The index pulse

indicates the zero position and is by default one angular step (1LSB) wide. However, it can be set to three LSBs by

programming the Index-bit of the OTP register accordingly (see Table 6).

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 13 - 33

Figure 8: Incremental Output Modes

Counterclockwise ccw

Step / Dir-Mode

Quad A/B-M ode

Index=0

1LSB

Index=1

3 LSB

Index

M echanical

Zero Position

LSB

Dir

Rotation Direction

Change

CSn

t Incremental outputs valid

t Dir valid

Hyst =

2 LSB

Clockwise cw

M ech anical

Zero Position

Incremental Power-up Lock Option

After power-up, the incremental outputs can optionally be locked or unlocked, depending on the status of the CSn pin:

CSn = low at power-up:

CSn has an internal pull-up resistor and must be externally pulled low (Rext ≤ 5kΩ). If Csn is low at power-up,

the incremental outputs (A, B, Index) will be high until the internal offset compensation is finished.

This unique state (A=B=Index = high) may be used as an indicator for the external controller to shorten the

waiting time at power-up. Instead of waiting for the specified maximum power up-time (0), the controller can

start requesting data from the AS5040 as soon as the state (A=B=Index = high) is cleared.

CSn = high or open at power-up:

In this mode, the incremental outputs (A, B, Index) will remain at logic high state, until CSn goes low or a low

pulse is applied at CSn. This mode allows intentional disabling of the incremental outputs until for example the

system microcontroller is ready to receive data.

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 2 LSB.

Regardless of the programmed incremental resolution, the hysteresis of 2 LSB always corresponds to the highest

resolution of 10 bit. In absolute terms, the hysteresis is set to 0.704 degrees for all resolutions.

For constant rotational directions, every magnet position change is indicated at the incremental outputs (see

Figure 9). If for example 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 2 LSB, until position „x+2“ is reached. Following this direction, the incremental outputs

will again be updated with every change of the magnet position.

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 14 - 33

Figure 9: Hysteresis Window for Incremental Outputs

Magn et Position

Hysteresis:

0.7°

X +2

Incrementa l

Output

Indication

Clockwise Direction

Countercl ockwise Dir ect ion

X +4

X +2

X +4

X +

X +1

X +3

9 Pulse Width Modulation (PWM) Output

The AS5040 provides a pulse width modulated output (PWM), whose duty cycle is proportional to the measured

angle:

()

1025 −

⋅

offon

on tt

Position

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 10: PWM Output Signal

1/fPWM

Angle

359.65 deg

(Pos 1023)

0 deg

(Pos 0)

1µs 1025µs

PWMIN

PWMAX

1024µs

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 15 - 33

Table 5: PWM Signal Parameters

Parameter Symbol Typ Unit Note

PWM frequency fPWM 0.9756 kHz Signal period: 1025µs

MIN pulse width PWMIN 1 µs

- Position 0d

- Angle 0 deg

MAX pulse width PWMAX 1024 µs

- Position 1023d

- Angle 359,65 deg

10 Analog Output

An analog output may be generated by averaging the PWM signal, using an external active or passive lowpass filter.

The analog output voltage is proportional to the angle: 0°= 0V; 360° = VDD5V.

Using this method, the AS5040 can be used as direct replacement of potentiometers.

Figure 11: Simple Passive 2nd Order Lowpass Filter

R1,R2 ≥ 4k7 C1,C2 ≥ 1µF / 6V

R1 should be ≥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.

11 Brushless DC Motor Commutation Mode

Brushless DC motors require angular information for stator commutation. The AS5040 provides U-V-W commutation

signals for one and two pole pair motors. In addition to the three-phase output signals, the step (LSB) output at pin 12

allows high accuracy speed measurement. Two resolutions (9 or 10 bit) can be selected by programming Div0

according to Table 6.

Mode 3.0 (3.1) is used for brush-less DC motors with one-pole pair rotors. The three phases (U, V, W) are 120

degrees apart, each phase is 180 degrees on and 180 degrees off.

Mode 3.2 (3.3) is used for motors with two pole pairs requiring a higher pulse count to ensure a proper current

commutation. In this case the pulse width is 256 positions, equal to 90 degrees.

The precise physical angle at which the U, V and W signals change state (“Angle” in Figure 12 and Figure 13) is

calculated by multiplying each transition position by the angular value of 1 count:

Angle [deg] = Position x (360 degree / 1024)

360°

R1 R2 analog out

Pin12

PWM

Pin7

VSS

0°

0V2

VDD2

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 16 - 33

Figure 12: U, V and V-signals for BLDC Motor Commutation (Div1=0, Div0=0)

C o mmu ta tion - M o d e 3 .0 (One-pole-pair)

Position: 0 171 341 512 683 853 0

Angle: 0.0 60.12 119.88 180.0 240.12 299.88 360.0

Width: 512 Steps Width: 512 Steps

CW Direction

Figure 13: U, V and W-signals for 2-pole BLDC Motor Commutation (Div1=1; Div0=0)

C ommu ta tio n - Mode 3 .2 (Two-pole-pairs)

Position: 0 85 171 256 341 427 512 597 683 768 853 939 0

Angle: 0.0 29.88 60.12 90.0 119.88 150.12 180.0 209.88 240.12 270.00 299.88 330.12 360.0

Width: 256 Steps W idth: 256 Steps

CW Direction

12 Programming the AS5040

After power-on, programming the AS5040 is enabled with the rising edge of CSn with Prog = high and CLK = low. 16

bit configuration data must be serially shifted into the OTP register via the Prog-pin. The first “CCW” bit is followed by

the zero position data (MSB first) and the incremental mode setting as shown in Table 6. Data must be valid at the

rising edge of CLK (see Figure 14).

After writing data into the OTP register it can be permanently programmed by rising the Prog pin to the programming

voltage VPROG. 16 CLK pulses (tPROG) must be applied to program the fuses (Figure 15). To exit the programming

mode, the chip must be reset by a power-on-reset. The programmed data is available after the next power-up.

Note: During the programming process, the transitions in the programming current may cause high voltage spikes

generated by the inductance of the connection cable. To avoid these spikes and possible damage to the IC, the

connection wires, especially the signals Prog and VSS must be kept as short as possible. The maximum wire length

between the VPROG switching transistor and pin Prog (see Figure 16) should not exceed 50mm (2 inches). To

suppress eventual voltage spikes, a 10nF ceramic capacitor should be connected close to pins Prog and VSS. This

capacitor is only required for programming, it is not required for normal operation.

The clock timing tclk must be selected at a proper rate to ensure that the signal Prog is stable at the rising edge of CLK

(see Figure 14). Additionally, the programming supply voltage should be buffered with a 10µF capacitor mounted

close to the switching transistor. This capacitor aids in providing peak currents during programming.

The specified programming voltage at pin Prog is 7.3 – 7.5V (see section 0). To compensate for the voltage drop

across the VPROG switching transistor, the applied programming voltage may be set slightly higher (7.5 - 8.0V, see

Figure 16).

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 17 - 33

OTP Register Contents:

CCW Counter Clockwise Bit

ccw=0 – angular value increases in clockwise direction

ccw=1 – angular value increases in counterclockwise direction

Z [9:0] Programmable Zero / Index Position

Indx Index Pulse Width Selection: 1LSB / 3LSB

Div1,Div0 Divider Setting of Incremental Output

Md1, Md0 Incremental Output Mode Selection

OTP Default Setting

The AS5040 can also be operated without programming. The default, un-programmed setting is shown in Table 6

(Mode 0.0):

CCW: 0 = clockwise operation

Z9 to Z0: 00 = no programmed zero position

Indx: 0 = Index bit width = 1LSB

Div0,Div1 : 00 = incremental resolution = 10bit

Md0, MD1: 00 = incremental mode = quadrature

Figure 14: Programming Access – Write Data (section of Figure 15)

Figure 15: Complete Programming Sequence

Data

CSn

Prog

CLKPROG

7.5V

VDD

tLoad PROG tPROG finished

Write Data Power OffProgramming Mode

tPROG

tPrgH

VProgOff

tPrgR

116

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 18 - 33

Figure 16: OTP Programming Connection of AS5040 (shown with AS5040 demoboard)

USB

Incremental Mode Programming

Three different incremental output modes are available.

Mode: Md1=0 / Md0=1 sets the AS5040 in quadrature mode.

Mode: Md1=1 / Md0=0 sets the AS5040 in step / direction mode (see Table 1)

In both modes, the incremental resolution may be reduced from 10 bit down to 9, 8 or 7 bit using the divider OTP bits

Div1 and Div0. (see Table 6 below ).

Mode: Md1=1 / Md0=1 sets the AS5040 in brushless DC motor commutation mode with an additional LSB

incremental signal at pin 12 (PWM_LSB).

To allow programming of all bits, the default factory setting is all bits = 0. This mode is equal to mode 1:0 (quadrature

A/B, 1LSB index width, 256ppr).

The absolute angular output value, by default, increases with clockwise rotation of the magnet (top view).

Setting the CCW-bit (see Figure 14) allows reversing the indicated direction, e.g. when the magnet is placed

underneath the IC:

CCW = 0 – angular value increases clockwise;

CCW = 1 – angular value increases counterclockwise.

By default, the zero / index position pulse is one LSB wide. It can be increased to a three LSB wide pulse by setting

the Index-bit of the OTP register.

Further programming options (commutation modes) are available for brushless DC motor-control.

Md1 = Md0 = 1 changes the incremental output pins 3, 4 and 6 to a 3-phase commutation signal. Div1 defines the

number of pulses per revolution for either a two-pole (Div1=0) or four-pole (Div1=1) rotor.

In addition, the LSB is available at pin 12 (the LSB signal replaces the PWM signal), which allows for high rotational

speed measurement of up to 30,000 rpm.

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 19 - 33

Table 6: One Time Programmable (OTP) Register Options

OTP-Mode-Register-Bit Pin # Pulses per

Revolution Incremental

Resolution

Mode Md1 Md0 Di v1 Div0 Index 3 4 6 12 ppr bit

Default (Mode0.0) 0 0 0* 0* 0* 1LSB

quadAB-Mode1.0 0 1 0 0 0 1LSB

quadAB-Mode1.1 0 1 0 0 1 3LSBs

2x256 10

quadAB-Mode1.2 0 1 0 1 0 1LSB

quadAB-Mode1.3 0 1 0 1 1 3LSBs 2x128 9

quadAB-Mode1.4 0 1 1 0 0 1LSB

quadAB-Mode1.5 0 1 1 0 1 3LSBs 2x64 8

quadAB-Mode1.6 0 1 1 1 0 1LSB

quadAB-Mode1.7 0 1 1 1 1

A B

3LSBs

PWM

10 bit

2x32 7

Step/Dir-Mode2.0 1 0 0 0 0 1LSB

Step/Dir-Mode2.1 1 0 0 0 1 3LSBs 512 10

Step/Dir -Mode2.2 1 0 0 1 0 1LSB

Step/Dir -Mode2.3 1 0 0 1 1 3LSBs 256 9

Step/Dir -Mode2.4 1 0 1 0 0 1LSB

Step/Dir -Mode2.5 1 0 1 0 1 3LSBs 128 8

Step/Dir -Mode2.6 1 0 1 1 0 1LSB

Step/Dir -Mode2.7 1 0 1 1 1

LSB Dir

3LSBs

PWM

10 bit

64 7

Commutation-

Mode3.0 1 1 0 0 0 10

Commutation-

Mode3.1 1 1 0 1 0

U(0º) V(120º) W(240º) LSB 3 x 1

Commutation-

Mode3.2 1 1 1 0 0 10

Commutation-

Mode3.3 1 1 1 1 0

U’

(0º,

180º)

V’

(60º,

240º)

W’

(120º, 300º) LSB 2 x 3

Note: Div1, Div0 and Index cannot be programmed in Mode 0:0

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/index 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 Z9:Z0 (see Figure 14) and programmed as described in section 12.

This new absolute zero position is also the new Index pulse position for incremental output modes.

Note: The zero position value may also be modified before programming, e.g. to program an electrical zero position

that is 180° (half turn) from the mechanical zero position, just add 512 to the value read at the mechanical zero

position and program the new value into the OTP register.

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 20 - 33

Repeated OTP Programming

Although a single AS5040 OTP register bit can be programmed only once (from 0 to 1), it is possible to program other,

unprogrammed bits in subsequent programming cycles. However, a bit that has already been programmed should not

be programmed twice. Therefore it is recommended that bits that are already programmed are set to “0” during a

programming cycle.

Non-permanent Programming

It is also possible to re-configure the AS5040 in a non-permanent way by overwriting the OTP register.

This procedure is essentially a “Write Data” sequence (see Figure 14) without a subsequent OTP programming cycle.

The “Write Data” sequence may be applied at any time during normal operation. This configuration remains set while

the power supply voltage is above the power-on reset level (see 0).

See Application Note AN5000-20 for further information.

Analog Readback Mode

Non-volatile programming (OTP) uses on-chip zener diodes, which become permanently low resistive when subjected

to a specified reverse current.

The quality of the programming process depends on the amount of current that is applied during the programming

process (up to 130mA). This current must be provided by an external voltage source. If this voltage source cannot

provide adequate power, the zener diodes may not be programmed properly.

In order to verify the quality of the programmed bits, an analog level can be read for each zener diode, giving an

indication whether this particular bit was properly programmed or not.

To put the AS5040 in analog readback mode, a digital sequence must be applied to pins CSn, Prog and CLK as

shown in Figure 17. The digital level for this pin depends on the supply configuration (3.3V or 5V; see section 14).

The second rising edge on CSn (OutpEN) changes pin Prog to a digital output and the log. high signal at pin Prog

must be removed to avoid collision of outputs (grey area in Figure 17).

The following falling slope of CSn changes pin Prog to an analog output, providing a reference voltage Vref, that must

be saved as a reference for the calculation of the subsequent programmed and unprogrammed OTP bits.

Following this step, each rising slope of CLK outputs one bit of data in the reverse order as during programming.

(see Figure 17: Md0-MD1-Div0,Div1-Indx-Z0…Z9, ccw)

During analog readback, the capacitor at pin Prog (see Figure 16) should be removed to allow a fast readout rate. . If

the capacitor is not removed the analog voltage will take longer to stabilize due to the additional capacitance.

The measured analog voltage for each bit must be subtracted from the previously measured Vref, and the resulting

value gives an indication on the quality of the programmed bit: a reading of <100mV indicates a properly programmed

bit and a reading of >1V indicates a properly unprogrammed bit.

A reading between 100mV and 1V indicates a faulty bit, which may result in an undefined digital value, when the OTP

is read at power-up.

Following the 16th clock (after reading bit “ccw”), the chip must be reset by disconnecting the power supply.

Figure 17: OTP Register Analog Read

Internal

test bit

digital Vunpro

rammed

Vpro

rammed

CSn

CLK 1 16

Prog

ProgEN

Md1Md0

Analog R eadback Data at P rog OutpEN

tLoadProg CLK

read

Prog changes to Output

Vref

Power-on-

Reset;

turn off

supply

Div1Div0 Z6 Z5 Z8 Z7 ccw Z9

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 21 - 33

13 Alignment Mode

The alignment mode simplifies centering the magnet over the chip to gain maximum accuracy and XY-alignment

tolerance.

This electrical centering method allows a wider XY-alignment tolerance (0.485mm radius) than mechanical centering

(0.25mm radius) as it eliminates the placement tolerance of the die within the IC package (+/- 0.235mm).

Alignment mode can be enabled with the falling edge of CSn while Prog = logic high (Figure 18). The Data bits D9-D0

of the SSI change to a 10-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 32 over a full turn.

The MagINCn and MagDECn indicators will be = 1 when the alignment mode reading is < 32. 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 360° turn of the magnet.

Stronger magnets or short gaps between magnet and IC may show values larger than 32. 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 mode by a power-on-reset (disconnect / re-connect power

supply).

Figure 18: Enabling the Alignment Mode

AlignMode enable

Prog

CSn

Read-out

via SSI

2µs

min.

2µs

min.

14 3.3V / 5V Operation

The AS5040 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 19).

For 5V operation, the 5V supply is connected to pin VDD5V, while VDD3V3 (LDO output) must be buffered by a

2.2...10µF capacitor, which is supposed to be placed close to the supply pin (see Figure 19).

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 (see Figure 19).

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 22 - 33

Figure 19: Connections for 5V / 3.3V Supply Voltages

LDO

2.2...10µF

100n

4.5 - 5.5V

Prog

Index_W

B_Dir_V

A_LSB_U

CLK

PWM_LSB

VDD3V3

VSS

VDD5V

5V Operation

Internal

VDD

CSn

LDO

100n

3.0 - 3.6V

VDD3V3

VSS

VDD5V

3.3V Operation

Internal

VDD

Prog

Index_W

B_Dir_V

A_LSB_U

CLK

PWM_LSB

CSn

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.

15 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 magnet’s field strength perpendicular to the die surface 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 20).

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 23 - 33

Figure 20: Typical Magnet and Magnetic Field Distribution

Mag net axis

Vertical fi el d

component

(45…75m T )

0 360

Vertical fie ld

component

R1 concentri c c i rcle;

radius 1.1m m

Magnet axi s

t yp. 6mm di am eter

S N

Physical Placement of the Magnet

The best linearity can be achieved by placing the center of the magnet exactly over the defined center of the IC

package as shown in Figure 21:

Figure 21: Defined IC Center and Magnet Displacement Radius

Defined

center

2.433 mm

3.9 mm 3.9 mm

rea of recommende d maximum

magnet misali gnment

Magnet Placement

The magnet’s center axis should be aligned within a displacement radius Rd of 0.25mm from the defined center of the

IC with reference to the edge of pin #1 (see Figure 21). This radius includes the placement tolerance of the chip within

the SSOP-16 package (+/- 0.235mm). The displacement radius Rd is 0.485mm with reference to the center of the chip

(see section 13: Alignment Mode)

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 24 - 33

The vertical distance should be chosen such that the magnetic field on the die surface is within the specified limits

(see Figure 20). The typical distance “z” between the magnet and the package surface is 0.5mm to 1.8mm with the

recommended magnet (6mm x 2.5mm). Larger gaps are possible, as long as the required magnetic field strength

stays within the defined limits.

A magnetic field outside the specified range may still produce usable results, but the out-of-range condition will be

indicated by MagINCn (pin 1) and MagDECn (pin 2), see Table 3.

Figure 22: Vertical Placement of the Magnet

1.282mm ± 0.15mm

0.576mm ± 0.1mm

Package surfaceDie surface

16 Simulation Modelling

Figure 23: Arrangement of Hall Sensor Array on Chip (principle)

With reference to Figure 23, a diametrically magnetized permanent magnet is placed above or below the surface of

the AS5040. The chip uses an array of Hall sensors to sample the vertical vector of a magnetic field distributed across

the device package surface. The area of magnetic sensitivity is a circular locus of 1.1mm radius with respect to the

center of the die. The Hall sensors in the area of magnetic sensitivity are grouped and configured such that

orthogonally related components of the magnetic fields are sampled differentially.

The differential signal Y1-Y2 will give a sine vector of the magnetic field. The differential signal X1-X2 will give an

orthogonally related cosine vector of the magnetic field.

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 25 - 33

The angular displacement (Θ) of the magnetic source with reference to the Hall sensor array may then be modelled

by:

()

°±

−

=Θ 5.0

21 21

arctan XX YY

The ±0.5° angular error assumes a magnet optimally aligned over the center of the die and is a result of gain

mismatch errors of the AS5040. Placement tolerances of the die within the package are ±0.235mm in X and Y

direction, using a reference point of the edge of pin #1 (Figure 23).

In order to neglect the influence of external disturbing magnetic fields, a robust differential sampling and ratiometric

calculation algorithm has been implemented. The differential sampling of the sine and cosine vectors removes any

common mode error due to DC components introduced by the magnetic source itself or external disturbing magnetic

fields. A ratiometric division of the sine and cosine vectors removes the need for an accurate absolute magnitude of

the magnetic field and thus accurate Z-axis alignment of the magnetic source.

The recommended differential input range of the magnetic field strength (B(X1-X2),B(Y1-Y2)) is ±75mT at the surface of

the die. In addition to this range, an additional offset of ±5mT, caused by unwanted external stray fields is allowed.

The chip will continue to operate, but with degraded output linearity, if the signal field strength is outside the

recommended range. Too strong magnetic fields will introduce errors due to saturation effects in the internal

preamplifiers. Too weak magnetic fields will introduce errors due to noise becoming more dominant.

17 Failure Diagnostics

The AS5040 also offers several diagnostic and failure detection features:

Magnetic Field Strength Diagnosis

By software: the MagINCn and MagDECn 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 is low, the magnet is either

moving towards the chip (MagINCn) or away from the chip (MagDECn).

Power Supply Failure Detection

By software: If the power supply to the AS5040 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 DO 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 3). In a failure case, either when the

magnetic field is out of range or the power supply is missing, these outputs will become low. To ensure adequate low

levels in case of a broken power supply to the AS5040, 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.

By hardware: Incremental outputs: In normal operation, pins A(#3), B(#4) and Index (#6) will never be high at the

same time, as Index is only high when A=B=low. However, after a power-on-reset, if VDD is powered up or restarts

after a power supply interruption, all three outputs will remain in high state until pin CSn is pulled low. If CSn is

already tied to VSS during power-up, the incremental outputs will all be high until the internal offset compensation is

finished (within tPwrUp).

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 26 - 33

18 Angular Output Tolerances

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 @ 25°C (see Figure 25).

Misalignment of the magnet further reduces the accuracy. Figure 24 shows an example of a 3D-graph displaying non-

linearity over XY-misalignment. 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 25 is repeated and the accuracy

(Errmax – Errmin)/2 (e.g. 0.25° in Figure 25) is entered as the Z-axis in the 3D-graph.

Figure 24: Example of Linearity Error over XY Misalignment

-1000

-800

-600

-400

-200

200

400

600

800

1000

-1000

-800

-600

-400

-200

200

400

600

800

1000

Linearity Error over XY-misalignment [°]

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.

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 27 - 33

Figure 25: Example of Linearity Error over 360°

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 outputs. It is specified as 0.12 degrees rms (1

sigma)*1.

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 applying an averaging of readings.

An averaging of 4 readings will reduce the transition noise by 6dB or 50%, e.g. from 0.12°rms to 0.06°rms (1

sigma).

 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)

*1: statistically, 1 sigma represents 68.27% of readings,

3 sigma represents 99.73% of readings.

linearit

error with centered ma

net

[

rees

]

-0.5

-0.4

-0.3

-0.2

-0.1

0.1

0.2

0.3

0.4

0.5

1 55 109 163 217 271 325 379 433 487 541 595 649 703 757 811 865 919 973

transition noise

Err

max

Err

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 28 - 33

High Speed Operation

Sampling Rate

The AS5040 samples the angular value at a rate of 10.42k samples per second. Consequently, the incremental, as

well as the absolute outputs are updated each 96µs. At a stationary position of the magnet, this sampling rate creates

no additional error.

Absolute Mode with Serial Communication:

With the given sampling rate of 10.4 kHz, the number of samples (n) per turn for a magnet rotating at high speed can

be calculated by:

srpm

⋅

In practice, there is no upper speed limit. The only restriction is that there will be fewer samples per revolution as the

speed increases.

Regardless of the rotational speed, the absolute angular value is always sampled at the highest resolution of 10 bit.

Likewise, for a given number of samples per revolution (n), the maximum speed can be calculated by:

rpm

⋅

In absolute mode with serial communication, 610 rpm is the maximum speed, where 1024 readings per revolution can

be obtained.

In incremental mode, the maximum error caused by the sampling rate of the ADCs is 0/+96µs. It has a peak of 1LSB

= 0.35° at 610 rpm. At higher speeds this error is reduced again due to interpolation and the output delay remains at

192µs as the DSP requires two sampling periods (2x96µs) to synthesize and redistribute any missing pulses.

Absolute Mode with PWM:

The principle is the same as with the serial communication. The PWM output is refreshed with a rate of 1.025ms, the

number of samples (n) per turn for a magnet rotating at high speed can be calculated by:

msrpm

n025.1

⋅

In absolute mode with PWM output, 57 rpm is the maximum speed, where 1024 readings per revolution can be

obtained.

Incremental Mode:

Incremental encoders are usually required to produce no missing pulses up to several thousand rpm’s.

Therefore, the AS5040 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).

Table 7: Speed Performance

Absolute Output Mode Incremental Output Mode

610rpm = 1024 samples / turn

1220rpm = 512 samples / turn

2441rpm = 256 samples / turn

etc…

no missing pulses

@ 10 bit resolution (512ppr):

max. speed = 30,000 rpm

Propagation Delays

The propagation delay is the delay between the time that a sample is taken until it is converted and available as

angular data. This delay is 48µs for the absolute interface and 192µs for the incremental interface.

Using the SSI interface for absolute data transmission, an additional delay must be considered, caused by the

asynchronous sampling (t= 0…1/fs) and the time it takes the external control unit to read and process the data.

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 29 - 33

Angular Error Caused by Propagation Delay

A rotating magnet will therefore cause an angular error caused by the output delay. This error increases linearly with

speed:

delayproprpmesampling .*6∗=

where: esampling = angular error [°]

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 that is processing

the data from the AS5040, thus reducing the angular error caused by speed.

Internal Timing Tolerance

The AS5040 does not require an external ceramic resonator or quartz. All internal clock timings for the AS5040 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 100µs (typ.)

 Incremental outputs:

the incremental outputs are updated every

100µs (typ.)

 PWM output:

A new angular value is updated every 100µs (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 section 9):

()

1025 −

⋅

offon

on tt

Position

Temperature

Magnetic Te m pera tu re Coe ffi cien t

One of the major benefits of the AS5040 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 coefficient, the AS5040

automatically compensates for the varying magnetic field strength over temperature. The magnet’s temperature drift

does not need to be considered, as the AS5040 operates with magnetic field strengths from ±45…±75mT.

Example:

A NdFeB magnet has a field strength of 75mT @ –40°C and a temperature coefficient of -0.12% per Kelvin.

The temperature change is from –40° to +125° = 165K.

The magnetic field change is: 165 x -0.12% = -19.8%, which corresponds to 75mT at –40°C and 60mT at 125°C.

The AS5040 can compensate for this temperature related field strength change automatically, no user adjustment is

required.

Accuracy over Temperature

The influence of temperature in the absolute accuracy is very low. While the accuracy is ≤ ±0.5° at room temperature,

it may increase to ≤±0.9° due to increasing noise at high temperatures.

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 30 - 33

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 (see Internal

Timing Tolerance).

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 31 - 33

19 Package Drawings and Markings

Figure 26: 16-Lead Shrink Small Outline Package SSOP-16

Dimensions

mm inch

Symbol Min Typ Max Min Typ Max

A 1.73 1.86 1.99 .068 .073 .078

A1 0.05 0.13 0.21 .002 .005 .008

A2 1.68 1.73 1.78 .066 .068 .070

b 0.25 0.315 0.38 .010 .012 .015

c 0.09 - 0.20 .004 - .008

D 6.07 6.20 6.33 .239 .244 .249

E 7.65 7.8 7.9 .301 .307 .311

E1 5.2 5.3 5.38 .205 .209 .212

e 0.65 .0256

K 0° - 8° 0° - 8°

L 0.63 0.75 0.95 .025 .030 .037

AYWWIZZ

AS5040

Marking: AYWW IZZ

A: Pb-free Identifier

Y: Last Digit of Manufacturing Year

WW: Manufacturing Week

I: Plant Identifier

ZZ: Traceability Code

JEDEC Package Outline Standard:

MO - 150 AC

Thermal Resistance Rth(j-a):

typ. 151 K/W in still air, soldered on PCB

IC's marked with a white dot or the letters

"ES" denote Engineering Samples

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 32 - 33

20 Packing Options

Delivery: Tape and Reel (1 reel = 2000 devices)

Tubes (1 box = 100 tubes à 77 devices)

Order # AS5040ASSU for delivery in tubes

Order # AS5040ASST for delivery in tape and reel

21 Recommended PCB Footprint

Recommended Footprint Data

mm inch

A 9.02 0.355

B 6.16 0.242

C 0.46 0.018

D 0.65 0.025

E 5.01 0.197

AS5040

Data Sheet

www.austriamicrosystems.com Revision 2.10 33 - 33

22 Copyrights

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.

23 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 lifesustaining equipment are specifically not recommended without additional processing by

austriamicrosystems AG for each application.

The information furnished here by austriamicrosystems AG is believed to be correct and accurate. However,

austriamicrosystems AG shall not be liable to recipient or any third party for any damages, including but not limited to

personal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or

consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the

technical data herein. No obligation or liability to recipient or any third party shall arise or flow out of

austriamicrosystems AG rendering of technical or other services.

Contact Information

Headquarters

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A-8141 Schloss Premstaetten, Austria

Tel: +43 (0) 3136 500 0

Fax: +43 (0) 3136 525 01

For Sales Offices, Distributors and Representatives, please visit:

http://www.austriamicrosystems.com/contact