Hi Max Roberson has been answering to my questions on the High speed interface forum and he suggested me to post the question here. Thanks Max.
I am looking to design a circuit with LVDS input but o/p must be 200mV pk-pk with Vocm=0-200mv (user programmable). I am looking at is 500Mhz speed but must have 100Mhz switching capability. This is DC coupled system. Further the RX side maintains a 200mV DIF-Z and I must detect a signal transition when TX side starts to drive a 200mV pk-pk signal with Vocm=200mv. So I will need a detection circuit also for transition detection. Any feedback will be helpful.
I understand - if your system needs to be able to support DC levels then AC-coupling is not a viable option. Your idea of using an amplifier circuit sounds good to me. TI has several fully differential amplifiers that allow for the output common mode to be set using a CM bias voltage input. I recommend contacting our high speed amplifiers team to see if they can provide some suggestions. Here is their support forum:
One thing to consider when picking out a device is the bandwidth that is needed. If you are trying to preserve the rise/fall times of your input signal, a rule of thumb for the minimum bandwidth is 0.35 divided by the 10%-to-90% transition time. You should also make sure that the amplifier's slew rate is fast enough to handle the data transitions.
Best regards, Max Robertson
You may want to look at either the LMH6552 or the LMH6554. Both can accomodate the bandwidth and common mode if used with split supplies (+-5V for LMH6552 or +-2.5V for LMH6554).
Neither will have an edge detection circuit. That would be something you would have to design separately.
Thanks for your response.
1. Is there an application note available for design with LMH6554?
2. Can I simulate with Tina-TI?
Thanks for your support.
You can use this application note (AN-2177):
I've attached a TINA simulation file that you could use as a starting point. LMH6554 Pspice Macromodel is already in TINA:
4276.LMH6554 SE to Diff ADC Driver with DC Offset 3_15_12.TSC
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