FEATURES

· 16/32/64/128/256 QAM demodulator

(DVB-C compatible : ETS 300-429).

· On chip 9-bit ADC.

· On chip PLL for crystal frequency

multiplication.

· Digital down conversion.

· Half Nyquist filters (roll off = 15 ).

· Automatic gain control PWM output

(AGC).

· Symbol timing recovery, with

programmable second order loop filter.

· Variable symbol rate capability from

SACLK/64 to SACLK/4

(SACLK max = 36 MHz)

· Programmable anti-aliasing filters.

· Full digital carrier recovery loop.

· Carrier acquisition range up to 8 of

symbol rate.

· Integrated adaptative equalizer (Linear

Transversal Equalizer or Decision

Feedback Equalizer).

· On chip FEC decoder (Deinterleaver &

RS decoder), full DVB-C compliant.

· DVB compatible differential decoding

and mapping.

· Parallel or serial transport stream

interface.

· I2C bus interface, for easy control.

· CMOS 0.35mm technology.

APPLICATIONS

· DVB-C fully compatible.

· Digital data transmission using QAM modulations.

· Cable demodulation.

· Cable modems

· MMDS (ETS 300-429).

DESCRIPTION

The VES1820X is a single chip channel receiver for 16, 32, 64, 128

and 256-QAM modulated signals. The device interfaces directly to

the IF signal, which is sampled by a 9-bit AD converter.

The VES1820X performs the clock and the carrier recovery

functions. The digital loop filters for both clock and carrier recovery

are programmable in order to optimize their characteristics

according to the current application.

After base band conversion, equalization filters are used for echo

cancellation in cable applications. These filters are configured as Tspaced

transversal equalizer or DFE equalizer, so that the system

performance can be optimized according to the network

characteristics. A proprietary equalization algorithm, independent of

carrier offset, is achieved in order to assist carrier recovery. Then a

decision directed algorithm takes place, to achieve final

equalization convergence.

The VES1820X implements a FORNEY convolutional deinterleaver

of depth 12 blocks and a Reed-Solomon decoder which corrects up

to 8 erroneous bytes. The deinterleaver and the RS decoder are

automatically synchronized thanks to the frame synchronization

algorithm which uses the MPEG2 sync byte. Finally descrambling

according to DVB-C standard, is achieved at the Reed Solomon

output. This device is controlled via an I2C bus.

Designed in 0.35 mm CMOS technology and housed in a 100 pin

MQFP package, the VES1820X operates over the commercial

temperature range.