Does propagation delay of the system decide the frequency of the system?

[sathi.ec]

Hi,

Is propagation delay of the system decides the frequency of the system?

Thanks regards

 

[bronzefury]

Re: Propagation Delay

Not necessarily. You'll need to understand the entire design to find the correct frequency. Are you designing something in particular?

 

[arunragavan]

Propagation Delay

propagation delay - u mean Tp(HL) and Tp(LH) is isnt?

there are ways by which u can reduce the propagation delay in large fan in circuits..

such as transistor sizing, prograssive transistor sizing, input re-ordering..

sometimes u can increase the switching speeds of the transistors also..

by increasin the w/l ratio, reduce the load capacitance.. reduce the startup resistance of the transistor or even by increasin the value of Vdd...

jes refer jan rabey book on digital integrated circuits..

wud help u..

 

[duet123]

Re: Propagation Delay

By doing pipelining, actually you can increase frequency.

 

[anjali]

Re: Propagation Delay

the propagation delay of the longest path of the system decides the operating freequency.

 

[bronzefury]

Re: Propagation Delay

In some applications, propagation delay may not be your only determining factor. You'll need to understand, at a higher level than propagation delay, how the overall chip operates. Usually, you want to understand the bounding frequencies of your design. That is, how low and how high of a frequency you could go and still have the chip work.

For example, if you were designing a DMA path, it would be a good idea to understand the characteristics of the data being DMA'd and the DMA controller. In other cases, altering frequencies between two clock domains could cause synchronization problems.

The next thing I would consider is cost.

I could keep rambling on, but I think you get the idea...

 

[phoenixfeng]

Propagation Delay

the max frequence is decided by the longest delay path

u should meet the follow :
Tco + Tcl_max + Tsu <= T + Tskew
Tco: Register delay from clk to output
Tcl_max: the max combinational logic delay
Tsu: Setup time
Tskew: CLock skew

 

[arunragavan]

Propagation Delay

anjali .. i think its critical path.. and not propagation delay..critical path is the longest path thru the circuit which decides the operational frequency of the circuit.

with regards,

 

[urgentor]

Re: Propagation Delay

I guess you're talking about the max freq of a board, not of a chip. For a board, if the clocking scheme is system synchronous, the propagation delay(accurately, flight time) determines the max freq of your board; while if the clocking scheme is source synchronized, by properly routing your board, there's no propagation/flight time difference between your clock/stobe signal and data bus, then the propagation/flight time will have no impact on your sysytem freq.
hope it helps.