NXP TDA18251HN硅调制器方案

       NXP 公司的TDA18251HN是第三代全集成，能大大地降低DVR / 多媒体 STB系统的总成本。TDA18251HN具有多标准数字/模拟有线接收功能，低功耗，频率高达1002 MHz，所有主要的调谐和RF特性都集成在一块芯片上。

      本文介绍了TDA18251HN的主要特性，以及DVR / 多媒体 STB前端参考板OM5785C 的主要指标和方框图。

                    图1 DVR / 多媒体 STB前端参考板OM5785C 外形图

       Total DVR / multimedia STB system costs can be reduced dramatically with NXP Semiconductors 3rd generation of fully integrated silicon tuners. By incorporating all the key, and often costly, components on chip, the TDA18251HN ensures you can easily and effectively meet industry demands for multi-tuner analog and digital video reception capabilities. It also offers ease-of-design and faster time-to-market, as well as helping you meet current and future performance requirements in HDTV and multimedia applications.

       主要优点：
       Highest performance levels for worldwide digital / analog cable TV reception
equal performance for master and slave tuners
       Lowest system cost
       eliminates external RF splitter
       no costly LNAs, SAW fi lters and incremental crystal oscillators required
       Easy on-board integration
       Smallest system PCB footprint
       Reduced external components

       主要特性：

       Full multistandard digital / analog cable reception
       Low power consumption
       Frequency coverage up to 1002 MHz
       All key tuning and RF features integrated on chip
       tracking fi lters for unwanted signal rejection
       IF selectivity (eliminating external SAW filters)
       tuner alignment
       integrated wide band gain control
       oscillators with no external components
       loop through
       Supports multi-tuner application without the need for an external RF splitter
       Four standby modes

       主要应用：
       Standard and HD (High Definition) set-top-boxes
       Multimedia set-top boxes
       Home entertainment servers
       DVR (Digital Video Recording)
       
       By integrating all key tuning functions and RF and IF selectivity on chip, NXP’s silicon tuner TDA18251HN reduces BoM and simplifies design. The architecture also eliminates additional discrete image-rejection filter, RF filters and IF SAW filters.

       On-chip integration of all these functions enables 4 channel DVR and multimedia cable STB boxes to be easily developed without an external splitter.

       The received signal spectrum is down-converted and filtered to low-IF signal, which directly feeds the input stage of the demodulator’s A/D converter, without the need of
conventional and costly external filtering. Operating on a 16 MHz crystal, the ICs buffered clock output can be used to provide the system clock to other tuners and channel decoders. The TDA18251HN also integrates 3 RF outputs, called MTO (Multi Tuner Output), for driving up to 3 slave tuners.

       Targeted at digital and analog cable applications it supports watch, record, video on demand and in home video distribution functions. Used in conjunction with the TDA8295HN (analog demodulator) and the TDA10023HN (digital channel demodulator), the TDA18251HN covers all worldwide digital and analog cable standards.

       DVR / 多媒体 STB前端参考板OM5785C 
       Complete reference board points the way
       To help cable set-top box makers develop straightforward, cost-effective multi-tuner  solutions, a DVR / multimedia STB front-end reference board OM5785C is        available. Featuring four TDA18251HN silicon tuners, it also includes four TDA10023HN QAM demodulators to support digital reception and four TDA8295HN demodulators for analog cable TV reception.

       Each TDA10023HN provides a transport stream output, while each TDA8295HN provides a CVBS SSIFD output.

       Via Multi-Tuner-Outputs, the master tuner provides the RF signal and clock frequency to the slave tuners. This in turn feeds the clock frequency to both QAM and analog
demodulators. Low profile shielding protects each tuner against EMI from the adjacent tuners and the environment.

       The user can control both QAM and analog demodulators via the I2C bus, and each QAM demodulator will then control the respective silicon tuner.

       DVR / 多媒体 STB前端参考板OM5785C 主要指标：

                                 图2 DVR / 多媒体 STB前端参考板OM5785C方框图

本文来源：NXP公司    作者：

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