At 04:31 PM 23/04/98 -0700, you wrote:
>Hi All,
>
>I am facing a big challenge and before I will go ahead I would like to
>ask anybody who has a good idea.
>The solution not need to be cost effective.
>I need to generate square wave with close to 50% duty cycle,
>but quartz precision.
>The frequencies are :   400Hz      -   4KHz   10Hz steps
>                                        4KHz       --   40KHz  100Hz steps
>                                        40KHz     --   400KHz 1000Hz steps
>                        400KHz     --   4MHz 10000Hz steps
>
>I really appreciate any idea.
>
>Thank You,
>
>Peter     ( schupet@dvp.com )
>
>

How close to 50%? A simple "D" type F/F will "Square" up the incoming
waveform. As for the rest a simple Johnson decade counter will provide the
/10 (And other programmable divide values below 10). As for the base
generator/divider, perhaps something like a 74HC4060 will do, as this will
take a highish ref frequency, of say 16 or 32MHz. If I remember correctly,
the first output on this will be 4MHz "Square"

Other than that, some form of PLL could be used say a 74HC4046, followed by
a programmable / by n counter. With this you will easy get greater
resolution. But may introduce more problems.

Other factors to consider including phase noise, jitter, long term accuracy/
stability etc (The list goes on).

Just remember that there is more than one or two possible solutions, you
will have to find the one that best suites your needs.


Dennis