HEDS-8933

HEDS-8933 Datasheet


Gray code correction can be switched on or off by putting the pin KORR =1 on or =0 off .

Part Datasheet
HEDS-8933 HEDS-8933 HEDS-8933 (pdf)
Related Parts Information
AEAS-7000-1GSG0 AEAS-7000-1GSG0 AEAS-7000-1GSG0
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AEAS-7000 Ultra-precision 16 bit Gray Code Absolute Encoder Module

Data Sheet

The encoder IC consists of 13 signal photo diode channels and 1 monitor photo diode channel and is used for the optical reading of rotary carriers i.e., discs . The photodiodes are accompanied with precision amplifiers plus additional circuitry.

The monitor channel is used to drive a constant current source for the highly collimated IR illumination system.

Functional Description

Background

The 13 signal channels are set up as:

Two precision defining signals A0, A09 , which are two 90° electrical shifted sine, cosine signals. These signals are conditioned to be compensated for offset and gain errors. After conditioning they are on chip interpolated
11 analog A1-A11 channels which are directly digitized by precision comparators with hysterisis tracking. The digitized signals are called D1-D11.

An internal correction and synchronization module allows the composition of a true 16 bit Gray code by merging the data bits of 1 and 2 by still keeping the code monotonic.

There is a Gray code correction feature for this encoder. This Gray code correction can be disabled/enabled by the pin KORR.

The gain and offset conditioning value of the sine and cosine signals are preloaded on-chip by factory. This will compensate for mechanical sensor misalignment error.
• Minimum mechanical alignment during installation
• Two Sine/Cosine true differential outputs with 1024
periods for unit alignment
• Integrated highly collimated illumination system
• 11 digital tracks plus 2 sin/cos tracks generate
precise 16 bit Gray code
• Ultra fast, 1 µs cycle for serial data output word equals 16 MHz
• On-chip interpolation and code correction
• MSB can be inverted for changing the counting
direction
• Internally built-in monitor track for tracking the light level of the LED.
• Watch dog with alarm output
• to +85°C operating temperature
• Rotary application up to 16 bit/360° absolute position
• Linear positioning system
• Cost effective solution for direct integration into

OEM systems

Signal-Channels A1-A11

The photocurrent of the photo diodes is fed into a trans-impedance amplifier. The analog output of the amplifier has a voltage swing of dark/light about V. Every output is transformed by precision comparators into digital signals D1-D11 . The threshold is at VDD/2 =Analog-reference , regulated by the monitor channel.

Monitor Channel with LED Control at Pins LEDR and LERR

The analog output signal of the monitor channel is regulated by the LED current. An internal bipolar transistor sets this level to VDD/2 control voltage at pin LEDR . Thus the signal swing of each output is symmetrical to VDD/2 =Analog-reference

The error bit at pin LERR is triggered if the Ve of the internal bipolar transistor is larger than VDD/2.

Signals Channels A0, A09 with Signal Conditioning and Calibration

These two channels give out a sine and cosine wave, which are 90 degree phase shifted. These signals have amplitudes which are almost constant due to the LED current monitoring. Due to amplifier mismatch and mechanical misalignment, the signals have gain and offset errors. These errors are eliminated by an adaptive signal conditioning circuitry. The conditioning values are on-chip preprogrammed by factory. The analog output signals of A0 and A09 are supplied as truedifferential voltage with a peak to peak value of V at the pins A09P, A09N, A0P, A0N.

Interpolator for Channels A0,A09

The interpolator generates the digital signals D0,D09 and D-1 to D-4. The interpolated signals D-1 to D-4 extend the 12 bit Gray code of the signals to form a 16 bit Gray code.

D0 and D09 are digitized from A0 and A09. The channels A0-A11 and A09 have very high dynamic bandwidth, which allows a real time monotone 12 bit Gray code at 12000 RPM.

The interpolated 16 bit Gray code can be used up to 1000 RPM only. At more than 1000 RPM, only the 12 bit Gray code from the MSB side can be used.

LSB Gray Code Correction Pin KORR

This function block synchronizes the switching points for the 11 bit Gray code of the digital signals D1 to D11 with D0 and D09 digitized signal of A0 and A09 .

The correction is not for the 4 excess interpolated bits of the 16 bit Gray code.

Gray code correction can be switched on or off by putting the pin KORR =1 on or =0 off .

MSBINV and DOUT Pins

The serial interface consists of a shift register. The most significant bit, MSB D11 will always be sent first to DOUT. The MSB can be inverted change code direction by using pin MSBINV.
Ordering Information

AEAS-7000-1GSD0

Single-turn, -25 to +85°C, detached encoder set, 5V, serial, 13 bit

AEAS-7000-1GSG0

Single-turn, -25 to +85°C, detached encoder set, 5V, serial, 16 bit

HEDS-8933

Mechanical Alignment Tool for AEAS-7000

Note For alignment process, please refer to Avago Technologies website for application note or contact factory.

AEA - 7000 - 1 G S 0

S - Standard to

D - 13 bits G - 16 bits

Legend
1 = 5V G = Gray code S = serial output mode

For product information and a complete list of distributors, please go to our web site:

Avago, Avago Technologies, and the A logo are trademarks of Avago Technologies, Limited in the United States and other countries. Data subject to change. Copyright 2006 Avago Technologies Pte. All rights reserved. Obsoletes 5988-9627EN 5989-4140EN - May 29, 2006
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Datasheet ID: HEDS-8933 520018