BCM312 5 PRODUCT Brief ® BCM312 5 QAMLink® UNIVERSAL TRANSMISSION SOLUTION B C M 3 1 2 5 F E AT U R E S S U M M A R Y • Integrated QAMLink • supports the ITU-T J.83 Annex A/B/C standards, as well as OpenCable™, DOCSIS/EuroDOCSIS, and DVB/DAVIC • Connects directly to Broadcom digital TV ICs supporting physical layer requirements including out-of-band • Integrated QPSK out-of-band receiver • Baseband interface to dual 6-bit A/D converters or IF • Represents a complete solution for dual • • • Integrated analog front end for the dual downstream • • downstream channels (in-band and out-of-band) and the upstream channel interface to signal A/D converter Variable symbol rate QPSK receiver Digital demodulator, Nyquist filters, tracking loops, and 4-tap adaptive decision feedback equalizer DigiCipher®II/DVB/DAVIC FEC decoder MPEG transport output interface/DAVIC MAC output interface and upstream blocks reduces board complexity and system costs • Serial control interface results in reduced overall pin count • Integrated upstream transmitter • Out-of-band QPSK receiver provides flexibility for • Programmable Starvue • • • IF or baseband inputs • Single, low-cost crystal solution eliminates costly II/DOCSIS™/EuroDOCSIS™/DVB/ DAVIC FEC encoder Pre-equalization filter Up to 6 MBaud variable rate QPSK/16-QAM modulator 10-bit D/A converter with output power control interfaces VCXOs • Includes direct interface to the OpenCable point-ofdeployment (POD) module • Single device supports both 6-MHz and 8-MHz channels • Control unit • Allows direct connection to Broadcom ICs to support • BSC/SPI compatible interface for configuration and • B E N E F I T S • Universal set-top and cable modem front-end in-band receiver 10-bit A/D converter with input AGC amplifier Variable symbol rate 256-QAM receiver Digital demodulator, Nyquist filters, tracking loops, and 32-tap adaptive decision feedback equalizer ITU-T J.83 Annex A/B/C compatible FEC decoder ® • • • O F additional data and video channels for DOCSIS/EuroDOCSIS/DAVIC systems and PVR settop boxes device control • RF tuner control 160-pin PQFP package Set-Top Box Block Diagram In-Band Channel Tuner Out-of-Band Channel Upstream Channel BCM3125 QAMLink® Universal Transmission Solution Audio BCM7020/BCM7030 High Definition Video / Graphics Subsystem CPU I/O Memory Video B C M 3 1 2 5 O V E R V I E W Variable Interpolator 10-bit D/A 0–65 MHz 10-bit A/D 36/44 MHz Pre-Equalizer Variable Interpolator Nyquist α = .25-.50 Variable Interpolator Nyquist α = .12-.18 FEC Phase Recovery and Variable Interpolator Nyquist α = .12-.18 32-tap 6-bit A/D IF/BB I Channel Variable Interpolator Nyquist α = .30-.50 IF/BB mode 6-bit A/D BB Q Channel 100-200 MHz LO Agile PLL Variable Interpolator DDS ITU-T J.83 Annex A/B/C FEC DFE IB Acquisition and Tracking Loops IB Tuner AGC MCNS DAVIC DDS Tuner Ctl. Tuner Control Starvue II DDS Amp Ctl. Amp Control Nyquist α = .25-.50 JTAG Int. OOB 4-tap DCII Equalizer DAVIC Nyquist α = .30-.50 OB Acquisition and Tracking Loops FEC Micro Int. US_CLK US_DATA US_ENAB US_CLAV US_SOC IB_CLK IB_DATA IB_SYNC IB_VALID IB_ERR JTAG Control OB_CLK OB_DATA OB_SYNC OB_VALID OB_ERR Micro Control OOB AGC The Broadcom BCM3125 combines an in-band 256-QAM receiver, an out-of-band QPSK receiver and a 4/16-QAM transmitter, providing an integrated set-top box or cable modem front-end solution. The in-band receiver in the BCM3125 directly samples a 36–44 MHz carrier frequency with a l0-bit A/D converter, which is preceded by a programmable gain amplifier (PGA). The inband demodulator consists of a quadrature mixer and multirate filters that convert the oversampled IF data stream to a baseband complex data stream. The I and Q baseband signals are then filtered by dual square-root Nyquist filters that can accommodate rolloff factors of 12–18% for various ITU-T J.83 Annex A/B/C applications. A 32-tap decision feedback equalizer (DFE) with 8 feed-forward taps and 24 feedback taps is implemented to remove the ISI generated by worst-case coaxial cable and wireless cable channels. The equalizer coefficients are updated every baud cycle for fast convergence. Two distinct forward error correction (FEC) methods are supported. The first standard, ITUT J.83 Annex A/C, is also referred to as the DVB, DVB interactive or DAVIC standard. The second, ITU-T J.83 Annex B, is variously known as DigiCipher®II, DOCSIS/EuroDOCSIS and SCTE DVS-031. Broadcom®, the pulse logo, QAMLink®, and Connecting everything® are trademarks of Broadcom Corporation and/or its subsidiaries in the United States and certain other countries. All other trademarks are the property of their respective owners. The out-of-band receiver in the BCM3125 contains a frequency agile oscillator that can downconvert any channel in the 70–130 MHz frequency range to a SAW centered IF. The desired channel is then subsampled by a 6-bit A/D converter at a rate that is more than 4 times the symbol rate. An additional 6-bit A/D is provided to allow for direct input of baseband signals The BCM3125 provides complete Starvue II, DOCSIS/EuroDOCSIS and DVB/DAVIC compatible 4/16-QAM upstream burst FEC encoder and modulator functionality. A 1-KB burst FIFO buffer provides input data rate decoupling. The FEC encoder consists of a programmable randomizer and Reed-Solomon encoder. There is also a programmable preamble prepend, symbol mapper, and transmitter pre-equalizer. The modulator consists of dual squareroot raised cosine filters with programmable excess bandwidth, α=0.25 or α=0.50, interpolation filters, and a digital upconverter which translates the shaped pulse to a digitally tunable RF center frequency from 0–65 MHz. A 10-bit D/A then converts this signal to an analog waveform with programmable output power levels. The BCM3125 includes an BSC/SPI interface for setup and control by the host processor. In addition, an RF tuner controller is also provided. ® BROADCOM CORPORATION 16215 Alton Parkway, P.O. Box 57013 Irvine, California 92619-7013 © 2002 by BROADCOM CORPORATION. All rights reserved. 3125-PB08-R 11.20.02 Phone: 949-450-8700 FAX: 949-450-8710 Email: [email protected] Web: www.broadcom.com