Scan SHIFT speed limitation

[Vincent Girard]

scan shift frequency in dft

Hi dft guys,

I was discussing with some guys, about scan shift speed and I
just wanted to have some clues coming from experts just like you all

The question is : What is limiting the scan shift on tester.

From what I know until now, The delay from the primary input ( pads ) to the first
scan flip flop is quite high. for example if this delay is 1ns this will be the maximum shift frequency I can reach, Is that correct ?

Waiting for your reply,

Regards

 

[santhosh007]

the scan power is also concern for not to running at high frequency.

 

[Vincent Girard]

That's right, The more you are making flops toggle at the same time the more power you need.
But I'm rather talking about timing issues.

 

[santhosh007]

I dont think any other reason. I ran max shift frequency of 125Mhz at the tester.

 

[joe2moon]

I mainly depends on how fast the tester can generate a clock pulse.

 

[Vincent Girard]

Thank you all for you answers,

I'd like to know which kind of testers are you using ?

( LTX, Agilent, VLCT ... others )

Which one do you think allows to have maximum shift frequency?