DM560P
V.90 Integrated Data/Fax/Voice/Speakerphone Modem Device Set
Preliminary
33
Version: DM560P-DS-P07
August 11, 2000
Chip 3 : DM6580 Analog Front End
Description
DM6580
The DM6580 is a single chip Analog Front End
(AFE) designed to be implemented in voice grade
modems for data rates up to 56000bps. The
DM6580 is an essential part the complete modem
device set. The AFE converts the analog signal into
digital form and transfers the digital data to the DSP
through the serial port. All the clock information
needed in a modem device is also generated in the
DM6580. Differential analog outputs are provided to
achieve the maximum output signal level. An audio
monitor with programmable volume levels is built in
to monitor the on-line signal. Inside the device, a
16-bit ADC and a 16-bit DAC with over-sampling and
noise-shaping techniques is implemented to
maximize performance.
The DM6580 offers wide-band transmit and receive
filters so that the voice band signal is transmitted or
received without amplitude distortion and with
minimum group delay. In order to support multi-mode
modem standards, such as V.90, V.34+, V.32bis,
V.32, V.22bis, V.22, V.23, V.21, Bell 212A, Bell 103,
V.17, V.29, V.27ter, programmable baud and data
rate clock generators are provided. For asymmetric
channel usage, the transmit and receive clock
generators are independent. In order to enhance
echo-cancellation, the receive clock is synchronized
with the transmit clock and the best receive timing
sample is reconstructed by a reconstruction filter.
The Transmit Digital Phase Lock Loop (DPLL) is
self-tuning to provide a master, slave or free-running
mode for the data terminal interface. A receive DPLL
that is step programmable by the host DSP is
implemented to get the best samples for the relevant
signal processing.
DM6580 Block Diagram
RxSCLK
RxDCLK
RFS
DOR
DIR
TFS
DOT
DIT
Digital
Reconstruction
Filter
SCLK
Digital
Interface
Rx Clock
System
Tx Clock
System
Divider
Control
Registers
Tx Filter &
DAC
Rx Filter &
ADC
LPF &
Attenuator
Voltage Reference
0/-6 dB
Audio Amplifier
Power-on
Detector
SPKR
RxIN
V REFN
V REFP
TxA2
TxA1
CLKIN
TxSCLK*2
TxDCLK
ExtCLK
V CM
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