LatticeECP3 offers both input and output LVDS buffers.
The LatticeECP3 device includes differential receivers in all banks. There are internal differential terminations available on the right and left sides which include banks 2, 3, 6, and 7(banks 3 and 6 do wrap around the bottom corners of the device, as well). This said, the inputs that include the differential terminations can be user programmed to utilize the terminations. LatticeECP3 includes 80-, 100-, and 120-ohm programmable resistors to match the system transmission line. Typical LVDS applications require 100-ohm differential terminations. Inputs that do not include the on-chip terminations such as the inputs in Bank 1 can be terminated with off-chip external termination resistors placed close to the device between the P and N pins. All differential inputs meet the published performance specifications in the datasheet (DS1021) with internal or external terminations.
LatticeECP3 does offer "True-LVDS" outputs. These outputs are also located on the right and left sides of the device as described above. However there is a subset of the available pins on the right and left side that can be used as "True-LVDS" outputs. "True-LVDS" output drivers meet both ac and dc-performance specifications published in the datasheet (DS1021). The designer can determine which outputs on the right and left sides support true-lvds by referencing the pin out tables available on www.latticesemi.com. The pin out tables highlight the available "True-LVDS" outputs available per device and package offering.
Users requiring more LVDS output pairs then can be supported with available "True-lvds" can use other available differential output pairs with external resistor biasing. This biasing technique is known-as "emulation" is detailed in DS1021. Emulated LVDS(LVDS25E) outputs are structured using source series and parallel resistor terminations located close to the device output. These resistors attenuate the signals from the differential LVCMOS output drivers and provide a matched source impedance to the transmission line as required by the LVDS specification. The use of LVDS25E outputs will meet the ac-performance of LVCMOS25 outputs and the dc-specifications of LVDS. Users should be aware of the difference in ac-performance using LVDS25E(emulated LVDS) outputs.
References:
DS1021 - LatticeECP3 Device Datasheet
TN1177 - LatticeECP3 sysIO Usage Guide