Hw to Calc max operating frequency for combinational ckt

[venkat25]

design of combinational ckt

Hi Friends,
I need to know the calculation method to find Max operating frequency. Can anyone tell the exact method to calculate the operating frequency...

I know how to calculate the frequency of a circuit between two flips

that is 1/(Tp1+Tp2+Tsetup).

Tp1 = 1st flipflop propagation Delay
Tp2 = combinational ckt propagation delay
Tsetup = 2nd flip flop setup time

but i not sure how to calculate the maximum operating frequency for a single
combinational circuit (example: inverter, NAND, AND etc)

Pls suggest me some good idea....

Thanks & Regds
Venkat

 

[venkat25]

max operating frequency flip flop

Hi Friends,
i having a Doubt that the Max operating frequency is calculated for a combinational cell like inverter, NAND etc ....
Is it essential ....?

Thanks & Regds
Venkat:|

 

[jent]

calculate maximum frequency propagation delay

Hi ,

There is no such maximum frequency specification for combinational circuits.
Rather we specify the propagation delay from each input pin to output pin .

In a real circuit scenario , most oftem combo logic comes in between -

1) flops
2) between input and flop
3) flop to output
4) input to output

in 1) we know the setup requirement and clk to q delay of flop
so that we can calculate the maximum frequency

2) we know the delay from input side and setup time of flop

3) Output timing requirement and flop clk to Q

4) Here we should know input delay and output requirement .

In summary max freq of a ckt depends on all these , flop chara combo delays ,
net delays and input/output timings ...