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Honored Contributor I
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Cyclone IV (EP4CE30F29) routing and B-LVDS connection

Hi all, 

 

i've got a problem and i hope you can help me. 

 

I'm working on project in which i am using many B-LVDS buses(114). And all of these buses are routed through EP4CE30F29. But here is the first problem. I want to use 4 memory chips DDR2 (4Gb each) and each on 16bits width data bus(two memory blocks 32bit wide). Chips use 1.5V and i probubly want to connect it to the banks 1,6,7 and 8. So this banks have to be powered by 1.5V supply. But BLVDS needs to be powered by 2.5V. So i need to connect BLVDS to banks powered with 1.5V power supply. (also there will be a SRAM chip) 

 

So i see this possibilities from my perspective: 

 

1,Use some ic level translator(but for B-LVDS i did not found anything) 

2,Use capacitors as DC coupling and use voltage dividers for setting DC offset to 1.5V/2 (but iam not sure if B-LVDS peripheral will work fine because in all documentation about B-LVDS is wrote that peripheral have to be supplied by 2.5V) 

3,Use just 2 DDR2 chips so use just 2 banks.(but iam not so happy to do this)  

 

Aaaaand another question about connection B-LVDS. I have many modules connecting to network ower B-LVDS. But i want to have it fail-safe. So do i have to connect each module over the pair of 100nF ceramic caps (as DC coupling) and shift DC offset internaly on each card(because of shorting bus or other problems).Now i have connected it directly. Did it tested it anyone? If iam right i can connect modules without DC blocking caps with modules with caps. 

 

Ideas? 

 

Can anyone help me with this problem? 

 

Many thanks for help!
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