AS5311
Data Sheet
AS5311
High Resolution Magnetic Linear Encoder
1 General Description
The AS5311 is a contactless high resolution magnetic
linear encoder for accurate linear motion and off-axis
rotary sensing with a resolution down to <0.5µm. It is
a system-on-chip, combining integrated Hall elements,
analog front end and digital signal processing on a
single chip, packaged in a small 20-pin TSSOP
package.
A multi-pole magnetic strip or ring with a pole length
of 1.0mm is required to sense the rotational or linear
motion. The magnetic strip is placed above the IC at a
distance of typ. 0.3mm.
The absolute measurement provides instant indication
of the magnet position within one pole pair with a
resolution of 488nm per step (12-bit over 2.0mm).
This digital data is available as a serial bit stream and
as a PWM signal.
Furthermore, an incremental output is available with a
resolution of 1.95 µm per step. An index pulse is
generated once for every pole pair (once per
2.0mm).The travelling speed in incremental mode is
up to 650mm/second.
An internal voltage regulator allows the AS5311 to
operate at either 3.3 V or 5 V supplies.
Depending on the application the AS5311 accepts
multi-pole strip magnets as well as multi-pole ring
magnets, both radial and axial magnetized (see
Figure 1 and Figure 3).
Figure 1: AS5311 with Multi-pole Magnetic Strip
for Linear Motion Sensing
Preliminary Data Sheet
The AS5311 is available in a Pb-free TSSOP-20
package and qualified for an ambient temperature
range from -40°C to +125°C.
2 Key Features
Two 12-bit digital absolute outputs :
- Serial interface and
- Pulse width modulated (PWM) output
Incremental output with Index
“red-yellow-green” indicators monitor magnet
placement over the chip
3 Applications
Micro-Actuator feedback
Servo drive feedback
Robotics
Replacement of optical encoders
Figure 2: Block Diagram of AS5311
VDD3V3
MagINCn
VDD5V
MagDECn
PWM
Sin
Ang
DO
Cos
Mag
CSn
CLK
A
B
AS5311
Index
Prog
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AS5311
Data Sheet
Figure 3: AS5311 with Multi-pole Ring Magnets for Off-axis Rotary Motion Sensing
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AS5311
Data Sheet
4 Table of Contents
1
2
3
4
5
General Description ...................................................................................................................... 1
Key Features ................................................................................................................................ 1
Applications.................................................................................................................................. 1
Table of Contents ......................................................................................................................... 3
Pinout .......................................................................................................................................... 5
5.1
5.2
6
Pin Assignments ..................................................................................................................... 5
Pin Description ....................................................................................................................... 5
Electrical Characteristics............................................................................................................... 6
6.1
6.2
6.3
Absolute Maximum Ratings ..................................................................................................... 6
Operating Conditions .............................................................................................................. 7
DC Characteristics for Digital Inputs and Outputs ..................................................................... 7
CMOS Schmitt-Trigger Inputs: CLK, CSn (CSn = internal Pull-up) ....................................... 7
CMOS Output Open Drain: MagINCn, MagDECn ................................................................ 7
CMOS Output: PWM ......................................................................................................... 7
Tristate CMOS Output: DO ................................................................................................ 8
6.3.1
6.3.2
6.3.3
6.3.4
6.4
6.5
6.6
Magnetic Input Specification.................................................................................................... 8
Electrical System Specifications .............................................................................................. 8
Timing Characteristics ............................................................................................................ 9
Synchronous Serial Interface (SSI) .................................................................................... 9
Pulse Width Modulation Output........................................................................................ 10
6.6.1
6.6.2
7
Detailed Description.................................................................................................................... 10
7.1
Incremental Outputs.............................................................................................................. 11
Incremental Power-up Lock Option .................................................................................. 11
7.1.1
7.2
7.3
Incremental Output Hysteresis............................................................................................... 12
Synchronous Serial Interface (SSI) ........................................................................................ 12
Data Contents ................................................................................................................ 13
7.3.1
7.4
Absolute Output Jitter and Hysteresis .................................................................................... 14
Adding a Digital Hysteresis ............................................................................................. 14
Implementing Digital Filtering .......................................................................................... 14
7.4.1
7.4.2
7.5
8
9
10
Z-axis Range Indication (“Red/Yellow/Green” Indicator) .......................................................... 14
Pulse Width Modulation (PWM) Output ........................................................................................ 15
3.3V / 5V Operation .................................................................................................................... 15
Magnet Specifications .............................................................................................................. 16
Magnetization .................................................................................................................... 16
Position of the Index Pulse ................................................................................................. 17
Mounting the Magnet ......................................................................................................... 17
Vertical Distance ......................................................................................................... 17
Alignment of Multi-pole Magnet and IC.......................................................................... 17
Lateral stroke of Multi-pole Strip Magnets ..................................................................... 17
10.1
10.2
10.3
10.3.1
10.3.2
10.3.3
11
Measurement Data Example ..................................................................................................... 19
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AS5311
Data Sheet
12
13
14
15
16
17
18
AS5311 Off-axis Rotary Applications ........................................................................................ 20
Package Drawings and Marking ................................................................................................ 21
Ordering Information ................................................................................................................ 22
Recommended PCB Footprint................................................................................................... 22
Revision History ...................................................................................................................... 23
Copyrights ............................................................................................................................... 23
Disclaimer ............................................................................................................................... 23
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AS5311
Data Sheet
5 Pinout
5.1 Pin Assignments
Figure 4: AS5311 Pin Configuration, TSSOP-20
NC
MagIncn
MagDecn
A
B
NC
Index
VSS
Prog
NC
1
2
3
4
5
6
7
8
9
10
20
19
18
NC
VDD5V
VDD3V3
NC
NC
PWM
CSn
CLK
DO
NC
AS5311
17
16
15
14
13
12
11
5.2 Pin Description
Pin 4(A), 5(B) and 7(Index) are the incremental outputs. The incremental output has a resolution of 10-bit per
pole pair, resulting in a step length of 1.95µm.
Note that Pin 14 (CSn) must be low to enable the incremental outputs.
Pins 12, 13 and 14 are used for serial data transfer. Chip Select (CSn; active low) initiates serial data transfer.
CLK is the clock input and DO is the data output. A logic high at CSn puts the data output pin (DO) to tri-state
and terminates serial data transfer. CSn must be low to enable the incremental outputs. See 7.1.1 for further
options.
Pin 8 is the supply ground pin. Pins 18 and 19 are the positive supply pins.
For 5V operation, connect the 5V supply to pin 19 and add a 2µ2…10µF buffer capacitor at pin 19.
For 3.3V operation, connect both pins 18 and 19 to the 3.3V supply.
Pin 9 is used for factory programming only. It should be connected to VSS.
Pins 2 and 3 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.
External pull-up resistors are required at these pins. See 6.3.2 for maximum output currents on these pins. Since
they are open-drain outputs they can also be combined (wired-and).
Pin 15 (PWM) allows a single wire output of the 12-bit absolute position value within one pole pair (2.0mm). The
value is encoded into a pulse width modulated signal with 1µs pulse width per step (1µs to 4097µs over one pole
pair).
Pins 6, 10, 11, 16, 17 and 20 are for internal use and must not be connected.
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