Clock Oscillators

Note: The clock oscillators are separate and not synchronous to the clock provided by the USB host interface.

In addition to the USB host interface clock, one fixed-frequency clock oscillator provides a reference clock for various FPGA components and systems.

  • Fabric / DDR4 Clock – This is a general-purpose 156.25 MHz clock for logic use. This clock should be used as the reference for designs using the DDR4 memory.

There is one 6 pin 3.2mm x 2.5mm 1.8V LVDS oscillator footprint available on the board that is not normally placed. This oscillator is connected to the MGT quad 225 refclock 1 input. It is designator U2 on the PCB. An example compatible component is the Skyworks 511JBA125M000CAGR.

Refclock 0 for the three MGT quads (banks 224, 225, and 226) are also brought out to the expansion connectors. See the Pins List for connection details.

Pin Mappings

Fabric / DDR4156.25 MHzJ23 / J24 (Bank 66)
MGT 225 Refclk 1Not PlacedT7 / T6 (Bank 225)
MGT 224 Refclk 0External (MC3)AB7 / AB6 (Bank 224)
MGT 225 Refclk 0External (MC3)V7 / V6 (Bank 225)
MGT 226 Refclk 0External (MC2)P7 / P6 (Bank 226)