What buffer for 20MHz clock from osc to 5 micros?

[Circlotron]

I’ve got a project where a 20MHz oscillator module has to supply five microcontroller clock inputs. The stated load for the oscillator module is 15pF so five micros would load it too much. Thought of using a 74AC04 hex inverter with section 1 that is fed from the oscillator module driving sections 2-6 inputs in parallel, and the five separate outputs go to the micros. Trouble is, I think the paralleled input capacitance of sections 2-6 would be too much load for section 1 output at 20MHz and 5 volts. Could anyone suggest a more suitable buffer? Clock skew is not an issue here.

[bson]

What voltage?  LVC logic has 4pF input capacitance and each 74LVC04 output will drive, if memory serves, 25mA.  It does have a maximum transition time on the input signal of 10ns, and keeping it down to 6-7ns is a good idea.

Oh, nvm, for some reason I missed you want 5V.  Can't you just use HC04's for fanout?

[RoGeorge]

What you are looking for it's called fanout, and it specifies how many inputs can a single output drive.  For 74AC I think the fanout is 15, so driving 5 x 74AC04 inputs from the output of another 74AC04 gate will be no problem.

[Circlotron]

Yeah, I thought that fanout figure would be frequency dependent so that’s why I mentioned 20MHz. Okay, I’ll look into that.

[Circlotron]

Can't you just use HC04's for fanout?

I would have thought a HC04 wouldn’t produce a convincing square wave at 20 megs. Haven’t actually tried one though.