Need help: LED display for V-II

[nge]

mbi50xx

Hi,

I would like to build LED display for Xilinx Virtex_II. I need to connect 64 LEDs to 64 bits of USER I/O. Could you give me any suggestion or info? Thanks.

Nge

 

[yego]

Some more details regarding the purpose of the display, the contents you'd like to display on it, and perhaps a handful of some other details would certainly help to start the discussion.
There are so many ways to wire your display that discussing all of them would be simply impossible, so be more specific describing your idea.
Regards, yego

 

[nge]

Thanks for your reply. I just want to observe the outputs from FPGA. The pins have 3.3V output. I am using Virtex-II which has 64 User I/O and I just want to connect them to 64 LEDs. I am not sure whether I can drive LEDs directly from FPGA using resister-LED combos. Do I need to use LED driver chip?

 

[yego]

If you are going to use high performance LEDs, you may drive them with c.a. 1mA of current, each, so in this case you can drive them directly from your FPGA pins.
Don't forget to limit the LED current with series resistors. Also observe the voltages needed to drive different kinds of LEDS. Some of them start as low as 1.5V while some need over 4V .
Should you require more detailed guidelines, feel free to ask.
regards, yego

 

[Big Boy]

Some problem may arise if you switch all the leds (or at least, many of them) ON or OFF at the same time.

You will pass from a state where all IO send no current to it will send a rush of current (tens of milli-amps). The problem is not the high current, but the rate at which it change. This can create a lot of bad inductive influence (cross-talk due to induction) at the transitions. This probably won't blow anything, but can make your FPGA run erratically.

Important: make sure you do use slow output slew rate (configurable as an output option). Anyway, you don't need fast slew rate for a LED since your eyes wouldn't make the difference anyway.

 

[YUV]

I am not sure whether I can drive LEDs directly from FPGA using resister-LED combos. Do I need to use LED driver chip?

Right! You really need a specific LED driver IC, because each LED will consumpt a quite large current. The total amount migt be huge. I am sure your FPGA will not stand it.
I would like to advice you MBI50xx series www.mblock.com.tw
or DM134 http://www.siti.com.tw/
Also, there are many other companies manufacture such chips.
Look at the photo, it is a ready to use RGB LED panel with common logic inputs, 3 driver ICs, a separate brightness adjustment for R,G and B colors. Driver ICs are covered by aluminum heatsink.

 

[eeeraghu]

In xilinx there are predefined codes in language templates, that may be useful

 

[zlop]

If you have many LEDs, due to the FPGA's current limit, don't connect them to the same bank--you can see the data sheet for further information. I suggest you to use special LED IC to design your project.
Good luck!