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BCM312 5
PRODUCT
(R)
Brief
OF BENEFITS
BCM312 5 QAMLink(R) UNIVERSAL TRANSMISSION SOLUTION
BCM3125 FEATURES SUMMARY
* Integrated QAMLink
* * * *
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
(R)
* Universal set-top and cable modem front-end
supports the ITU-T J.83 Annex A/B/C standards, as well as OpenCableTM, DOCSIS/EuroDOCSIS, and DVB/DAVIC supporting physical layer requirements including out-of-band downstream channels (in-band and out-of-band) and the upstream channel and upstream blocks reduces board complexity and system costs count
* Connects directly to Broadcom digital TV ICs * Represents a complete solution for dual
* Integrated QPSK out-of-band receiver
* * * *
* Baseband interface to dual 6-bit A/D converters or IF
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(R)II/DVB/DAVIC FEC decoder MPEG transport output interface/DAVIC MAC output interface
* Integrated analog front end for the dual downstream * Serial control interface results in reduced overall pin * Out-of-band QPSK receiver provides flexibility for
IF or baseband inputs VCXOs
* Integrated upstream transmitter
* Programmable Starvue * * *
II/DOCSISTM/EuroDOCSISTM/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
* Single, low-cost crystal solution eliminates costly * Includes direct interface to the OpenCable point-ofdeployment (POD) module channels
* Control unit *
* Single device supports both 6-MHz and 8-MHz * Allows direct connection to Broadcom ICs to support
additional data and video channels for DOCSIS/EuroDOCSIS/DAVIC systems and PVR settop boxes
* BSC/SPI compatible interface for configuration and
device control * RF tuner control 160-pin PQFP package
Set-Top Box Block Diagram
In-Band Channel
BCM3125
QAMLink(R) Universal Transmission Solution
Audio BCM7020/BCM7030 High Definition Video / Graphics Subsystem Video
Tuner
Out-of-Band Channel
Upstream Channel
CPU
I/O
Memory
BCM3125
OVERVIEW
Variable Interpolator 0-65 MHz 10-bit D/A
Nyquist = .25-.50
Pre-Equalizer
Starvue II MCNS DAVIC
US_CLK US_DATA US_ENAB US_CLAV US_SOC
DDS
Variable Interpolator Variable Interpolator Nyquist = .25-.50 Nyquist = .12-.18 Phase Recovery and Variable Interpolator Nyquist = .12-.18 32-tap DFE
FEC
Amp Control
Amp Ctl.
ITU-T J.83 Annex A/B/C FEC
IB_CLK IB_DATA IB_SYNC IB_VALID IB_ERR
36/44 MHz
10-bit A/D
DDS
Tuner Control IB Tuner AGC IF/BB I Channel
Tuner Ctl.
IB Acquisition and Tracking Loops 6-bit A/D IF/BB mode Variable Interpolator Nyquist = .30-.50 4-tap Equalizer Variable Interpolator Nyquist = .30-.50 6-bit A/D
JTAG Int.
JTAG Control
OOB DCII DAVIC FEC
OB_CLK OB_DATA OB_SYNC OB_VALID OB_ERR
BB Q Channel
100-200 MHz LO OOB AGC
Agile PLL
DDS
OB Acquisition and Tracking Loops
Micro Int.
Micro Control
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(R)II, DOCSIS/EuroDOCSIS and SCTE DVS-031.
Broadcom(R), the pulse logo, QAMLink(R), and Connecting everything(R) 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, =0.25 or =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.
(R)
BROADCOM CORPORATION 16215 Alton Parkway, P.O. Box 57013 Irvine, California 92619-7013
(c) 2002 by BROADCOM CORPORATION. All rights reserved. 3125-PB08-R 11.20.02
Phone: 949-450-8700 FAX: 949-450-8710 Email: info@broadcom.com Web: www.broadcom.com

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