AS5040(2004) View Datasheet(PDF) - austriamicrosystems AG
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AS5040 Datasheet PDF : 20 Pages
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AS5040 10-BIT PROGRAMMABLE MAGNETIC ROTARY ENCODER
Pin 11 Chip Select (CSn; active low) selects a device within
a network of AS5040 encoders. A “logic high” at CSn forces
the digital tri-state output into the high ohmic state. A “high”
pulse with a minimum duration of tCSn also initiates a
subsequent readout of the current angular value.
Pin 12 allows a single wire output of the 10bit absolute
position value. The value is encoded into a pulse width
modulated signal ((absolute position code + 1) µs). By
using an external low pass filter, the PWM angular position
output can be converted to an analog voltage, making a
direct replacement of potentiometers possible.
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 MagINCn and MagDECn that indicate movements
of the used magnet towards or away from the device’s
surface.
A small low cost diametrically magnetized (two-pole)
standard magnet provides the angular position information
(see Figure 15).
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). This PWM
signal output also allows the generation of a direct
proportional analogue voltage, by using an external Low-
Pass-Filter.
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 according to Table
7. As long as no programming voltage is applied at pin
PROG, the new setting can 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 zapped
(see Figure 12). The default setting represents the
quadrature A/B mode including the Index signal with a pulse
width of 1 LSB. The Index signal is logic high at the user’s
programmed position.
The AS5040 is tolerant to magnet misalignment and
magnetic stray fields due to differential measurement
technique and Hall sensor conditioning circuitry.
Sin
Hall Array
Cos
&
Frontend
Amplifier
DSP
Ang
Absolute
Mag
Interface
(SSI)
OTP
Register
Programming
Parameters
Incremental
Interface
Revision 1.1
Figure 3 AS5040 Block Diagram
www.austriamicrosystems.com
MagINCn
MagDECn
CSn
DO
PW M_LSB
CLK
A_LSB_U
B_Dir_V
Index_W
Prog
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