Xilinx OBUF attributes on Spartan3

Brian, thanks for the links, I also work with ISE 7.1SP4
Marco

Hi Marco,
So, for a cap

V = Q / C.

Let's say we want 3V rise, C = 11pF, we can drive 24mA, so

3 = 24mA * t / 11pF  , where t is time.

t = 3 * 11pF / 24mA = 1.375 ns.

You can see the probe's capacitance is limiting the rise time you're 
measuring. 24mA takes 1.4 nS to charge the 'scope probe's capacitance. I 
think you need a faster scope and a FET probe, maybe 2GHz and a probe 
capacitance of 1-2pF. Or ask Xilinx for some data?

HTH, Syms.



"Marco" <marco@marylon.com> wrote in message 
news:1138366454.747563.55520@g49g2000cwa.googlegroups.com...
> They're 11.1pF and 10MOhm, also 500Mhz bandwith.
> Marco
> 

Symon, thanks, do agree with what you wrote, it's straight and simple.
Thanks