Hej Allan
Læs om fasedetektor/fasekomparatorer funktioner og typer her:
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Citat: "... Phase Detector: Let's have a look at the basic phase detector. There are actually two basic types, sometimes referred to as Type I, and Type II. The Type I phase detector is designed to be driven by analog signals or digital square-wave signals, whereas the Type II phase detector is driven by digital transitions (edges). They are typified by the most common used 565 (linear Type I) and the CMOS 4046, which contains both Type I and Type II. ..."
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Citat: "... The issue with phase/frequamcy comparators is that they must work and correct the error under all circumstances, with both frequencies widely different, and also with identical frequenceis, but a small phase difference. That limits the playing field. Many decades ago, Motorola created a circuit (I think it was calle 4044 or something like it) that did this job beautifully. I once converted this design into FPGA land, see
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What you do with the bang-bang outputs is up to you. You can integrate them and feed a VCO, or control an up-down counter... ... > What you do with the bang-bang outputs is up to you. You can integrate > them and feed a VCO, or control an up-down counter...
Yes, that'll be the 74HC4046 (also variants as 74HC7046).
This device data has good phase detector info.
Some comments on PLL detectors :
Some designs use two, one for coarse (effectively Freq) lock, and one for fine (effectively phase) lock.
If you are seriously worried about PLL/VCO sidebands, better PLL detectors have deliberate dead-band removal - this is extra logic that prevents a 'flat spot' in the phase/voltage curve, that can occur in simpler digital-state only designs. ..."
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I pdf side 3-6:
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Denne har god 74xx fanout, da denne type kan synke og løfte mere strøm på udgangene:
Her er 3 fasekomparatorer at vælge mellem: Side 6 med gate-diagram:
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/Glenn