TMS320F280049M: What is FSI?

Hello Sasaki and Gautam,

FSI, or Fast Serial Interface (no extra creative marketing points being awarded for this name), originated as a solution for higher bandwidth digital communication across the air gap, or hot-side to cold-side and vice versa, in high voltage systems such as those used in industrial drives and digital power applications.  In particular, the goals also included lowering the total cost of (reinforced) isolation associated with spanning the air gap as well as making the silicon cost impact small as well.  So, we needed to be serial and stay with standard LVCMOS IO buffers (not more expensive LVDS buffers, for example).  See the Venn diagram below comparing FSI to some of the other options.  

FSI achieves the top clock rate of 50MHz for LVCMOS IO and can take as few as two pins, CLK and Data, in each direction.  FSI is also dual-data rate.  It latches the data on both the rising and falling clock edges making the raw transmit bandwidth 100Mbps and the raw receive bandwidth 100 Mbps as well.  

The configuration of 2 signals in each direction that also requires reinforced isolation is addressed perfectly by another TI component, the ISO7842.  A single SOIC16 packaged ISO7842 is all that is needed to isolate the 100 Mbps FSI signals up to 8000 Vpk and carries reinforced isolation certifications according to VDE, CSA, CQC, and TUV.  This single chip when using FSI can replace the cost of multiple isolation devices while saving significant board space and also reducing the PCB routing and voltage plane definition challenges associated with mixed-plane, high voltage PCB designs.

We do believe that the F28004x MCU family will find its way into many hot-side sensing and control applications where it will need to communicate with a cold side MCU or MPU (on the cold-side due to the need to have its communications interface circuits, Ethernet, CAN, etc. isolated from the high voltage power electronics/supplies).

The FSI can also serve well for direct high-speed, low pin-count, chip-to-chip communications when both devices exist on the same voltage plane, too.  You could imagine two F28004x devices side by side using FSI to share data (for comparison?) very quickly between each other.  

As to the devices that can "talk" FSI, well today that is limited to the F280045 and F280049 from C2000.  But you can expect to see it on future C2000 devices as well as possible support from other "cold-side" processors as well.  Sorry, I can't give more details than that here.

Please note that FSI is available with a few different pin mux options depending upon the package type (64 QFP sampling today).  You can learn more about FSI at Section 5.11.7 in the F28004x datasheet and Section 26 of the Technical Reference Manual.

Let me know what your ideas are for how you could apply this new technology in your systems!