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datasheet中有SMPTE 对SDI接口的几点要求：TI recommends placing the LMH1208 as close as possible to the 75-Ω BNC ports to meet SMPTE specifications.
1. Return Loss: This specification details how closely the port resembles 75-Ω impedance across a specified frequency band. The LMH1208 features a built-in 75-Ω return-loss network on SDI_OUT1 and SDI_OUT2 to minimize parasitics and improve overall signal integrity.
2. AC Coupling: AC-coupling capacitors are required for transporting uncompressed serial data streams with heavy low-frequency content. The use of 4.7-μF, AC-coupling capacitors is recommended to avoid lowfrequency DC wander.
3. Rise/Fall Time: Output 75-Ω signals are required to meet certain rise and fall timing depending on the data rate. This improves the eye opening observed for the receiving device. The LMH1208 SDI_OUT1 and SDI_OUT2 cable drivers feature programmable edge rate adjustment to meet SMPTE rise and fall time requirements.
