
Preliminary Product Information
This document contains information for a new product.
Cirrus Logic reserves the right to modify this product without notice.
1
Copyright
Cirrus Logic, Inc. 1997
(All Rights Reserved)
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
CS6420
Full-Duplex Speakerphone Chip
Features
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
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
BANDGAP
AO
DGND
NI
DATA
STROBE
DRDY
CLKI
CLKO
API
RST
Mcrocontroller Interface
NO
AVDD
DVDD
AVDD
NC4
NC3
NC2
NC1
AGND
A
0,6,9.5,12dB
H
F
R
R
S
H
M
C
D
Σ
+
-
Pre-Emphasis
Filter
Network
Echo Canceller
A
0,6,9.5,12dB
F
H
T
S
T
H
C
M
D
Σ
+
-
Filter
Echo Canceller
Acoustic
Pre-Emphasis
APO
MB
34 dB
1 k
2.12V
3.5V
Clock
Generation
JUN ‘97
DS205PP2