DDR2 signal measurements

[ku637]

Hi,

I have a board designed with DDR2. I want to check certain timing parameters in the existing design.Clock Frequency is 150MHz.

I have a oscilloscope Lecroy 620zi 2GHz, 2 Active probes HFP2500 2.5GHz, and one differential probe AP034 , 1GHz.

I want to measure the timing specification of DDR2 device MT47H64M16HW like input setup time and hold time shown below,




if i make all single ended measurements as shown in figure 32 it will take 3 active probes which i don't have ( CK,CK#,say 1 Address signal)
So I want to measure the clock CK and CK# with a differential probe. So i will get a single waveform, not two as shown in figure like CK and CK#.
But the concern is in order to measure the setup time and hold time the figure 32 make use of the crossing point of CK and CK# signals , which i wont be getting. So anybody can suggest me if it is possible or what is the correct way?

Thanks,

 

[KlausST]

Hi,

make use of the crossing point of CK and CK# signals , which i wont be getting.

For sure you get it.
The crossing point is when both voltages are equal. U1 = U2.
The differential probe shows "U2 - U1" ..... and if both voltages are equal it shows exactely 0V.

--> The crossing point is exactely at zero voltage of the differential probe.

Klaus

 

[malli_1729]

Yes. Every point in both single ended signals can get on differential signal also...