That 'HC7046 had a lock-detect output that showed some promise, but wasn't terribly useful. It took the place of one of the phase comparators.

I miss the old parts that Signetics made for PLL applications, notably the NE564, which had a 50 MHz oscillator. Sadly, it had only the XOR (leading to quadrature lock) phase detector, but that one would settle at the center frequency, unlike the edge-coupled types offered by the 'HC7046.

TI specified their 'HCT7046 as having a center frequency of 21 MHz at steering voltage of half Vcc. That's with specific values of passives, and its maximal frequency at 38 MHz with no capacitance at C1 and infinite resistance (presumably open circuit) for R2 at Vcc=4.5 volts. I have little confidence in the stability, hence, the usefulness of that set of figures.

I suppose one could recreate the old-style PLL's in that range between 10 MHz and 80 MHz using a couple of ECL components including a comparator as a VCO and a level shifter, but it was nicer when one could use a single component and still get satisfactory results.

RE