In what applications does the propagation delay need to be considered?

[chang830]

Hi,
I noticed some product gives the spec of propagation delay while some others not. I wonder in what applications, the propagation delay spec needs to be specillay consideraed?

Thanks

 

[master_picengineer]

propagation delay

Hi,
If you talk about delay in the context of VLSI, this should be taken into account for garanteeing the synchronization between the different blocs of the IC. There is two kind of delays: delay in interconnects and in the clock network.
If these delay are not handled carefully the IC will be unfunctionnal. In fact the problem is a question of having data signal and clock pulses such that hold and setup time are respected.

 

[JPR75]

Re: propagation delay

Hi,

You need to considerate it specially in application where synchronization between clock/data or data/data are needed.
Image you have a clock of 100 MHz and you want to sample a data flow (...01...) with this clock on a SDRAM and a FPGA.
The data go trough some components and arrive to the SDRAM 12ns later then to the FPGA. You will simple 0 in the SDRAM and 1 in the FPGA, instead of 0 and 0.

Regards
-------------
electrocoop

 

[tvincent]

Re: propagation delay

Regarding probabagation delay. A basic description is: the data needs to arrive before the clock pluse, by a specificed number of microseconds before the clock. This spec should be in the data sheet of the part you are using.