Thank you for reaching out to Intel FPGA Community.
According to the part number given by you, the device is from Altera’s FLEX 10K device family. For your information, the device have been discontinued so I have limited source to find it. I managed to obtained the device datasheet but could not find any clue to answer your question. You can refer to Product Discontinuance Notification below:
Thank you for your understanding.
I try to look up on the suffix code through this link FPGA Device Part Numbers but still could not found the letter "B".
I currently contacting my internal team and will get back to you as soon as I can once I got the information.
Thank you for your patience. What I got from the internal team is that the "B" code is meant for customer code. This means that the OPN is for a specific customer that requires special instructions for the product at that time.
Usually we use two alphabets for customer code (AA, AB, AC etc…) but in this case of FLEX 10KE/S OPN, having 2 alphabets cause the number of allowed characters of 18 to be exceeded. So, we truncate one alphabet off.
I hope this helps.