CS6420

2

DS205PP2

TABLE OF CONTENTS

Absolute Maximum Ratings ..............................................................................................4

Recommended Operating Conditions..............................................................................4

Power Consumption ..........................................................................................................4

Analog Characteristics ........................................................................................................4

Analog Transmission Characteristics..............................................................................5

Microphone Amplifier ........................................................................................................5

Digital Characteristics .......................................................................................................5

Overview ............................................................................................................................8

Functional Description .....................................................................................................8

Analog Interface .......................................................................................................8

Acoustic Interface ..............................................................................................9

Network Interface ............................................................................................10

Microcontroller Interface .........................................................................................10

Description ......................................................................................................10

Register Definitions .........................................................................................11

Register 0..................................................................................................12

Mic - Microphone Preamplifier Enable ...............................................12

TSD - Transmit Suppression Disable.................................................12

GB - Graded Beta ..............................................................................12

ACC - Acoustic Coefficient Control ....................................................13

RVol - Receive Volume Control .........................................................13

TGain - Transmit Analog Gain ...........................................................13

Register 1..................................................................................................14

HD - Half-Duplex Disable...................................................................14

RSD - Receive Suppression Disable .................................................14

Taps - AEC/NEC Tap Allocation ........................................................15

NCC - Network Coefficient Control ....................................................15

TVol - Transmit Volume Control.........................................................15

RGain - Receive Analog Gain............................................................15

Register 2..................................................................................................16

NErle - Network ERLE Threshold ......................................................16

NFNse - Network Full-Duplex Noise Threshold .................................16

RHDet - Receive Half-Duplex Detection Threshold ...........................17

HDly - Half-Duplex Holdover Delay....................................................17

NseRmp - Background Noise Power Estimator Ramp Rate..............17

RSThd - Receive Suppression Threshold..........................................17

PCSen- Path Change Sensitivity .......................................................17

Register 3..................................................................................................18

AErle - Acoustic ERLE Threshold ......................................................18

AFNse - Acoustic Full-Duplex Noise Threshold.................................18

THDet - Transmit Half-Duplex Detection Threshold ..........................18

TSAtt - Transmit Suppression Attenuation.........................................19

TSBias - Transmit Suppression Bias .................................................19

TSThd - Transmit Suppression Threshold .........................................19

HHold - Hold in Half-Duplex on Howl.................................................19

Reset ...............................................................................................................19

Clocking ..................................................................................................................19

Power Supply .........................................................................................................20

Power Down Mode ..........................................................................................20

Noise and Grounding ......................................................................................21

Design Considerations ...................................................................................................22

Algorithmic Considerations .....................................................................................22

Full-Duplex Mode ............................................................................................22

Theory of Operation ..................................................................................22

Adaptive Filter ...........................................................................................23

Pre-Emphasis ....................................................................................23

Graded Beta.......................................................................................23

Update Control ..........................................................................................24