CS6420
Full-Duplex Speakerphone Chip
Features
General Description
Most modern speakerphones use half-duplex operation,
which switches transmission between the far-end talker
and the speakerphone user. This is done because the
acoustic coupling between the speaker and microphone
is much higher in speakerphones than in handsets
where the coupling is mechanically suppressed.
The CS6420 enables full-duplex conversation with a sin-
gle-chip solution. The CS6420 can easily replace
existing half-duplex speakerphone ICs with a huge in-
crease in conversation quality.
The CS6420 consists of telephone & audio interfaces,
two codecs and an echo-cancelling DSP.
ORDERING INFORMATION
CS6420-CS
CDB6420
20-pin SOIC
Evaluation Board
l
Single-chip full-duplex hands-free operation
l
Automatic gain control
l
Optional 34 dB microphone preamplifier
l
Integrated mute and volume control
l
Integrated 80 dB IDR dual codec
l
Speech-trained Network and Acoustic Echo
Cancellers
l
Powerdown mode
l
Microcontroller Interface
DGND
NC4
NC3
NC2
NC1
Rx
Suppression
Half Duplex
AGND
Mute/Volume
Control
AVDD
High Pass
Filter
ADC
NI
0,6,9.5,12 dB
DAC
+
-
Σ
RxAGC
AO
Pre-Emphasis
Filter
Network
Echo Canceller
Acoustic
Echo Canceller
-
Pre-Emphasis
Filter
Clock
Generation
CLKI
CLKO
Mute/Volume
Control
Tx
Suppression
Half Duplex
Hgih Pass
Filter
TxAGC
DAC
NO
Σ
ADC
1 kΩ
34 dB
0,6,9.5,12 dB
2.12 V
BANDGAP
3.5 V
API
+
Microcontroller Interface
DVDD
DATA
STROBE
DRDY
RST
AVDD
APO
MB
Preliminary Product Information
Cirrus Logic, Inc.
Crystal Semiconductor Products Division
P.O. Box 17847, Austin, Texas 78760
(512) 445 7222 FAX: (512) 445 7581
http://www.crystal.com
This document contains information for a new product.
Cirrus Logic reserves the right to modify this product without notice.
Copyright
©
Cirrus Logic, Inc. 1997
(All Rights Reserved)
JUN ‘97
DS205PP2
1
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