dm6437zdu ibis疑问

fh1037723204

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在TI官网下载DM6437ZDU的IBIS模型c641c_zdu_ddr,并加载到Hyperlynx中，对单一网络T_DDR_A10_2进行SI分析，使用Terminator Wizard。结果如附件所示，显示”Warning driver impedance is rather large. Wide driver impedance tolerance may hinder terminator."请问这是什么原因导致的？还有如果Driver impedance过大会有什么影响？
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chq_yanxue

直接点击“Apply Value”

TanAiHeong

Hi, this mean the output impedance of your driver(may get from the IBIS model) is large and your series terminator may not be effective. However, this is depend on the Zo of your topology. Based on the figure, it shows your Zo is controlled at 76Ohm(which is quite high for single ended signaling, std is 50Ohm +/- 10% and 60Ohm is acceptable) and the suggested value is ~20Ohm to match with your effective Zo. So, your whole channel will be simulated at ~60Ohm. If the driver impedance is too quite and significantly out of the Z0 range, it may cause multiple voltage reflection which lead to an underdamped/undamped issues

格林杨

Driver impedance 过大难道不是会失配引起反射吗