LMH2180 75 MHz Dual Clock Buffer

Dear Timothy,

Thank you very much for your clear answer. Unfortunately these time are far to long

for my application: switching TCXO outputs (25MHz, clipped sine, 0.8Vpp) with switching

times in the order of a few nsec!! Do yopu have a suggestion for an alternative?

Thanks,

Sam

Hi Sam,

If you require an dual channel analog clock buffer to preserve the clipped sine signal, you could use a dual op amp with low-noise and disable feature in unity-gain configuration.  One possible option is OPA2836 which has a disable time of 25 ns and enable time of 200 ns (typical) at Vs = 2.7 V.

If you are OK with converting the clipped sine wave to a square wave, the LMK00105 (5 outputs) is a LVCMOS buffer with Hi-Z capability, 1.5 to 3.3V adjustable output supply, and synchronous output enable (OE).  The OE control input is synchronized to the input clock to ensure runt-pulse-free operation when the OE toggled H to L (disabled) or L to H(enabled).  The enable/disable time is 2 input clock cycles typical (3 cycles max).  So with a 25 MHz input clock, the typical enable/disable time will be between 80 to 120 ns.

Best regards,

Alan

Hi Alan,

Thanks for your thorough reply. I do indeed need to preserve the clipped sine property, the processor chip which needs to be clocked requires this. I need to switch from one clock to another. I can't however miss any clock cycle, that's why I am looking for devices with enable/ disable times in the order of a few nanoseconds. I may have found CMOS switches which do have this property. Do you have alternative suggestions?

Again, thanks

Sam

Hi Alan,

Yes, I guess that's the way to go. I found one switch with on/ off times in the order of 5nsec, that should do the trick. And thanks for your remarks about cross-talk etc.

Regards, Sam