NSDS25CP104应用解决方案

NS 公司的LVDS 4x4 交叉点开关DS25CP104芯片的功能非常齐备，数据传输速率高达3.125Gbps,可以提高信号的完整性，符合XAUI电信设备及 SMPTE 424M专业级视频系统的严格要求。以功耗为例来说，这款产品的每通道功耗只有122mW，而且无论以电缆还是FR-4底板传送信号，这款芯片都增强或均衡处理来自FPGA 或专用集成电路(ASIC)的信号。这款芯片的共模输入电压范围极为宽泛，因此无需采用耦合电容器也可支持低电压正射极耦合逻辑(LVPECL)、电流模式逻辑(CML)及LVDS等信号电平。系统设计工程师可以利用外置引脚控制功能或串行的系统管理总线(SMBus)进行配置，因此配置DS25CP104芯片时有更大的灵活性。这款交叉点开关电路还设有8kV的静电释放(ESD)保护功能，而且LVDS输入/输出引脚更另有100-Ohm 的终端装置，因此可减少插入损耗和元件数目，进而缩小电路板面积。DS25CP104提供业界无与伦比的10ps抖动性能，适用于电信设备、视频路由系统以及自动化测试应用.

3.125 Gbps 4x4 LVDS Crosspoint Switch with Transmit Pre-emphasis
and Receive Equalization



The DS25CP104 is a 3.125 Gbps 4x4 LVDS crosspoint switch optimized for high-speed signal routing and switching over lossy FR-4 printed circuit board backplanes and balanced cables.
Fully differential signal paths ensure exceptional signal integrity and noise immunity. The non-blocking architecture allows connections of any input to any output or outputs. The switch configuration can be accomplished via external pins or the System Management Bus (SMBus) interface.
The DS25CP104 features four levels (Off, Low, Medium, High) of transmit pre-emphasis (PE) and four levels (Off, Low, Medium, High) of receive equalization (EQ) settable via the SMBus interface. Off and Medium PE levels and Off and Low EQ levels are settable with the external pins. In addition, the SMBus circuitry enables the loss of signal (LOS) monitors that can inform a system of the presence of an open inputs condition
(e.g. disconnected cable).
Wide input common mode range allows the switch to accept signals with LVDS, CML and LVPECL levels; the output levels are LVDS. A very small package footprint requires a minimal space on the board while the flow-through pinout allows easy board layout. Each differential input and output is internally terminated with a 100Ω resistor to lower device insertion and return losses, reduce component count and further minimize
board space.

主要特性:
■ DC - 3.125 Gbps low jitter, low skew, low power operation
■ Pin and SMBus configurable, fully differential, nonblocking architecture
■ Pin (two levels) and SMBus (four levels) selectable preemphasis and equalization eliminate ISI jitter
■ Wide Input Common Mode Range enables easy interface to CML and LVPECL drivers
■ LOS circuitry detects open inputs fault condition
■ On-chip 100Ω input and output termination minimizes insertion and return losses, reduces component count and minimizes board space
■ 8 kV ESD on LVDS I/O pins protects adjoining components
■ Small 6 mm x 6 mm LLP-40 space saving package

应用:
■ SD/HD/3GHD SDI Routers
■ OC-48 / STM-16
■ Fibre Channel (2GFC)
■ InfiniBand and FireWire

图1.方框图:



图2.典型应用:



图3.抖动性能测试电路图



图4.预加重性能测试电路



图5.均衡性能测试电路



图6.预加重和均衡性能测试电路



下面是DS25CP104 评估套件的性能介绍

The DS25CP104EVK is an evaluation kit designed for demonstrating performance of
DS25CP104, a 3.125 Gbps 4x4 LVDS Crosspoint Switch with Transmit Pre-emphasis
and Receive Equalization. The evaluation kit is comprised of the DS25CP104 with its
associated input and output SMA connectors and jumpers to manually select the desired pre-emphasis or equalization. The kit also includes an integrated USB to SMBus conversion circuit to control the SMBus with a PC, and three FR4 striplines (15” (38.1cm), 30” (76.2cm), and 60” (152.4cm) ) to exercise the devices’ signal conditioning features (pre-emphasis and equalization).
The purpose of this document is to familiarize the user with the DS25CP104EVK, to
suggest test setup procedures and instrumentation to test the device optimally, and to
guide the user through some typical measurements that demonstrate the performance of the DS25CP104 in typical applications.

下面图7是DS25CP104 评估板外形图:



下面是相关的应用电路图以及材料清单(BOM):









详情请见数据表:

http://cache.national.com/ds/DS/DS25CP104.pdf


和评估板用户手册:

http://www.national.com/appinfo/lvds/files/ds25cp104evk_manual.pdf