Can I use clock with frequency lower than 125 MHz for DDR2 ?

[bigyellow]

Hi,

As we know, in principle the DDR2 requires at least 125MHz clock frequency. Is it a problem if I use a clock which is a little slower than 125MHz, say 122M-124M?

 

[Iouri]

DDR2 clock frequency

Why do you want to use slower clock???

 

[bigyellow]

DDR2 clock frequency

because I have system clock in this frequency, if I could do this, this is the easiest way.

 

[echo47]

DDR2 clock frequency

Your frequency is still pretty close to the allowable range, so my guess is it would probably still work fine, but you should ask the manufacturer for advice.

The DDR2 probably contains a DLL that generates internal timing signals based upon your input clock. A DLL generally operates over a limited frequency range. If you operate outside of that range, then you risk malfunction.

 

[cfriend]

DDR2 clock frequency

I used DDR2 in 100MHz, it is ok

 

[Iouri]

DDR2 clock frequency

you still need to have FIFO for your DDRAM controller, use separate clock on FIFO