CPLD for project

Thread Starter

shaklack

Joined Aug 1, 2020
1
hello,
I am looking for a vary fast CPLD for my project, i need to output one shot nanoseconds pulse with the fastest rise and fall down speed.
I will be vary appreciated if some one could suggest me the best one.
 
The rise and fall times for a CPLD output is a complicated parameter. Data sheets provide setup and hold times and propagation delays but rise and fall times for general purpose outputs, not so much. A lot depends on what is loading the pin. In general, IBIS or Spice modeling is done to determine the rise and fall times for specific conditions. Or, actual measurements which are difficult without the right kind of oscilloscope and probe. In my experience, 2 nanoseconds rise or fall time is a reasonable number for a device such as a MAX10 from Intel. Again, what is the load? What rise and fall times do you need? Some of the specialized outputs are very fast with subnanosecond timing but these are output types like LVDS.

Edit: Going much faster then a couple of nanoseconds starts to cause problems such as ground bounce. So, general purpose outputs will, in general, not go much faster. These problems are so common that many CPLDs have the option to slow down the output slew rate. For example, the MAX10 device I mentioned earlier has fast, medium and slow options for general purpose outputs. Slew rate control saved me once when I had a large number of outputs switching at the same time. I had to use the slow option.
 
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