9.2.1.2 Detailed Design Procedure
Follow this design procedure for bidirectional I/O applications:
- Select a power supply that meets the DC and AC requirements in Recommended Operating Conditions.
- Choose a small 0402 surface-mount ceramic capacitor for AC-coupling capacitors to maintain characteristic impedance.
- Choose a high-quality, 75-Ω BNC connector that can support 2.97-Gbps applications. Consult a BNC supplier regarding insertion loss, impedance specifications, and recommended footprint for meeting SMPTE return loss.
- Follow detailed high-speed layout recommendations provided in Layout Guidelines to ensure optimal signal quality when interconnecting 75-Ω and 100-Ω signals to the LMH0397.
- Determine whether SPI or SMBus communication is necessary. If the LMH0397 must be programmed with settings other than what is offered by pin control, users must use SPI or SMBus Mode for additional programming.
- Configure EQ/CD_SEL, OUT0_SEL, and SDI_OUT_SEL pins according to the desired default use case. In a bidirectional I/O application, the EQ/CD_SEL pin or register settings may be modified to switch between EQ Mode and CD Mode.
- Configure the LMH0397 in EQ Mode. Tune the HOST_EQ0 100-Ω driver control pin to equalize the PCB output trace following OUT0±. Use register control for more tuning options if necessary.
- Configure the LMH0397 in CD Mode. Tune the SDI_VOD output amplitude control pin for optimal signal quality depending on the cable length attached at SDI_IO+ and SDI_OUT+. Use register control for more tuning options if necessary.