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Can 74VHC4040 work at 250MHz clock input ?? Anyone?

Can 74VHC4040 work at 250MHz clock input ?? Anyone?

Can 74VHC4040 work at 250MHz clock input ?? Anyone?

(OP)
Hi all,
        I have a situation here...I am trying to do some very precise frequency counting. I am trying to use 74VHC4040 in the design at 250MHz with gate charge dissipation resistor to ground (47Ohm) at clock input.will that work?  74VHC4040 spec sheet says Fmax=210MHz...Has anyone used this config before? or have any suggestions...I am trying to take count output on latches only when the counting is over....Let me know if more info i needed.

RE: Can 74VHC4040 work at 250MHz clock input ?? Anyone?

Is this a one-off?  You'd be insane to base a product on this.  Not only is your desired speed 19% over the absolute maximum but it's 208% over the maximum over temperature!!

That said if you raise the voltage further you might have a better chance on a one-off.  Notice how much faster the part gets with voltage.  Maybe run it at 6.8V - you might get to 250Mhz.   Otherwise just get the smallest CPLD or FPGA and define a 4040 in it that will run at 2-3Ghz.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Can 74VHC4040 work at 250MHz clock input ?? Anyone?

Looking at the Fairchild data sheet the minimum guaranteed operating frequency is 150MHz at 5V with minimum load capacitance. Don't bother, even for a one off. It just won't be reliable. Use a divide by two pre-scaler in front of it to make it useable.

RE: Can 74VHC4040 work at 250MHz clock input ?? Anyone?

Consider using a Philips/NXP 74ALVC74 as a divide by 2 pre-scalar. This will run above 300MHz at 3.3V according to the datasheet.

RE: Can 74VHC4040 work at 250MHz clock input ?? Anyone?

Not a problem, IF you run it at something like -20ÂșC.  CMOS runs faster at colder temperatures.

TTFN

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RE: Can 74VHC4040 work at 250MHz clock input ?? Anyone?

(OP)
Thank you all....I decided to prescale both input frequencies / 16 and they both should work good with that chip....Just for sharing with you guys , I did few tests and 74VHC4040 does work at 250MHz without a problem provided you have gate charge dissipation resistor. But cannot risk it letting it out for manufacturing. I mainly decided not to use that since there was skew in the output when i pushed it to 200MHz and above limit.....I needed skew to be less than 0.01% & it turned out to be 0.05%  and the only capacitance in the output was that of oscilloscope probe (~10pF)..... Thanks again for sharing with me your thoughts....

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