ADC0809 Clock signal

[Andy Roark]

Hello group,

I am trying to find a simple, stand alone clock circuit or part for an ADC0809. The ALE pin for my mC is not an acceptable solution in this particular case. Any ideas of suggestions would be greatly appreciated.

 

[williB]

Hello group,

I am trying to find a simple, stand alone clock circuit or part for an ADC0809. The ALE pin for my mC is not an acceptable solution in this particular case. Any ideas of suggestions would be greatly appreciated.

well you could use an off the shelf oscillator , and divide it down..to an acceptable speed..
what is your projected sampling speed?

 

[Andy Roark]

I wanted to get an input in the range of 500 khz (suggested on data sheet). I was not aware I could divide down clock outputs. I'll do my homework and figure out how to make that work.

Any quick links to tutorials would be greatly appreciated. I currently have a 12Mhz oscillator on the board to drive the 8051 and will probably try to use that.

 

[williB]

12,000,000/32 =375000
so since 2^5 = 32 :: one 74LS161 counter and one flip flop will get you 375Khz..
in other words you arent going to get 500KHZ from a 12 MHZ oscillator..
but you could buy a 1MHZ oscillator and use one flip flop to divide it in half..

 

[FRIED]

Could use two 7493 to divide by 24.

 

[Andy Roark]

Thanks for the help guys.

I finally went with the ALE pin (12*1/6 = 2Mhz) sent through a 163 for a final signal of 1Mhz.

That did the trick for me. Up and running