Make 16MHz from 32MHz Cheap

[kodabear]

I was wondering if anyone knew of a cheap way to make 16MHz from a 32MHz clock very cheaply. I also need this to be stable. The 32MHz drives one processor, and the 16MHz will drive another.

Thanks

 

[StanStep3]

Why not use a flip flop set up to toggle? This will divide the incoming frequency by two.

best of luck,
Stan

 

[melone]

Go with a PLL. If these are clock signals, then don't mess around. By the way, do these clock have to be in sync?

 

[nbucska]

TIs 74AHCT is good for 60MHZ, $.11 to $.38 ea. for 1000
( depending package etc.)


<nbucska@pcperipherals.com>

 

[kodabear]

The two processors communicate asyncronously. Would there be extra EM emissions due to using a flip-flop? The second processor is a SCSI controller. I need to ensure data integrity. I am not quite sure how the flip-flop would effect that.

 

[IRstuff]

Did you think that there are no flip-flops in either processor?

EM control is done through proper grounding, shielding and bypassing. A poor design will cause inverters to have problems.

TTFN

 

[melone]

Well....... In general, I would agree, except in this case, perhaps simply inserting flop could cause some unforseen effects. If the original signal has rise and fall times in the 50-100ns range, and the flop is in the 5-10ns range, there might be some EM issues. BUT, the way to fix those issues is by doing exactly what you stated.

 

[IRstuff]

True enough, but he is talking about a 32 Mhz clock, which means a half-period of 15.6 ns, so rise and fall times have to on the order of 5 ns or better to begin with.

TTFN

 

[kodabear]

Flip flop it is. Thank you all for your help.

 

[nbucska]

If the rise/fall is slow add delay into the /Q to D
feedback. ( IC or RC )

<nbucska@pcperipherals.com>