TI E2E Community
High Speed Interface
High Speed Interface Forum
Looking for a LVDS buffer with Vocm= 0mv to 300mv (user Defined) and Vout=200mv pk-pk
Looking for a LVDS buffer with Output common mode voltage of 0mv to 300mv (user Defined). Most LVDS buffers have 1.2V VCM Out. Is there a way to create such a buffer using amplifier circuit and be able to simulate the behavior. Vout pk-pk is required to be 200 mV. Any feedback will be helpful.
The 1.2-V common mode voltage is part of the LVDS specification, so you aren't likely to find any LVDS devices with such a low common mode. The simplest solution in my opinion is to just use series capacitors to AC-couple the buffer's differential output and then set the common mode to the desired level by using bias resistors at the receiver. I have attached a TI application note that goes into more detail on how to AC-couple different types of differential buffers to one another. In particular, you may want to take a look at Figures 9 though 11, which show three different methods of setting a receive-side common mode.
Please let me know if you have any questions.
Best regards,Max RobertsonAnalog Applications EngineerTexas Instrumentsmfirstname.lastname@example.org
First Thanks for your kind response. Problem is that I must DC Couple in order to carry Link Start DC conditions used by the Receiver. This is a Special receiver which looks for such conditions at 200mV. I was planning on using National/TI's ADC Differential Driver Buffers which allow VOCM to be adjustable to a defined Reference. I am not sure whether they will do the job or not? Any ideas using analog devices 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
Thanks Max, I have posted it there now. Thanks for your feedback.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.