DS26303短程线路接口单元与IDT82V2048的比

接收器

在接收侧，IDT82V2048要求端接阻抗为12.4Ω (T1 3.3V模式)，9.31Ω (E1 75Ω同轴)或者15Ω (E1 120Ω双绞线)。当使用外部阻抗模式时，DS26303的所有情况都要求用15Ω端接电阻；当使用DS26303的软件选取阻抗匹配模式，不需要任何电阻。IDT82V2048要求使用1kΩ电阻同RTIP和RRING管脚串联。如果DS26303采用软件选取端接/阻抗匹配模式，这些1kΩ的电阻可以用0Ω电阻代替。


图1. LIU前端电路图

表11. LIU前端值 ModeComponent75Ω Coaxial120Ω Twisted Pair100Ω/110Ω Twisted PairTx CapacitanceCt560pF (typ). Adjust for board parasitics for optimal return loss.Tx ProtectionDtInternational Rectifier: 11DQ04 or 10BQ060 Motorola: MBR0540T1Rx Transformer 1:2TFrPulse: T1124 (0°C to +70°C)Tx Transformer 1:2TFtPulse: T1114 (-40°C to +85°C)Tx Decoupling (ATVDD)C1Common decoupling for all eight channels is 68µF.Tx Decoupling (ATVDD)C2Recommended decoupling per channel is 0.1µF.Rx Decoupling (AVDDn)C3Common decoupling for all eight channels is 68µF.Rx Decoupling (AVDDn)C4Common decoupling for all eight channels is 0.1µF.Rx TerminationC5When in external impedance mode, Rx capacitance for all eight channels is 0.1µF. Do not populate if using internal impedance mode.Rx TerminationRtWhen in external impedance mode, the two resistors for all modes shall be 15.0Ω ±1%. Do not populate if using internal impedance mode.Voltage ProtectionTVS1SGS-Thomson: SMLVT 3V3 (3.3V transient suppressor)

 

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