Re: OT: MC12080 prescaler chip weirdness


Ed Breya
 

Is this a deal where you're just adding the 12080 to an existing board in the counter, or are you building the whole prescaler from scratch? Also, what frequencies and input levels are you using to test it with? The 12080 should work just fine if you apply it according to the datasheet, and have the right RF/HF environment around it. RF prescalers like this one must be AC coupled, and have a minimum cutoff frequency depending on the coupling cap size, and need sufficient amplitude and edge speeds to get proper operation. If the signal input isn't right, you can get strange results, and it can self-oscillate when the signal is not present or too small. Odd things can happen if you overdrive it too. Also, don't overlook the bypass caps - besides good supply bypassing, one is needed on the unused differential input.

Ed

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