At 09:30 AM 8/20/01 -0700, you wrote:
>        Is all this worth the effort to save 50 cents or whatever for a
ceramic
>resonator with built-in capacitors? The resonator even takes less board
>space (unless you go surface mount with the resistor and capacitor).

It's a cute idea, but I'd go with the resonator. +/-0.5% accuracy, one part,
(it can be surface mounted too) and no issues with line voltage noise screwing
things up. I don't see a lot of use for a transformerless power supply with
a baud rate generator, but there are undoubtedly some. Resonators are
dirt-cheap in large quantity, and are very robust.

I see four basic application areas:

no accurate timing required:            use RC(preferably internal calibrated)
                                                or LC (5-10% accuracy, or worse)
                                                (cost $0.00 to $0.05 in qty)

baud rate timing:                               use a resonator (0.5% accuracy)
                                                (cost $0.10 in qty)

accurate timing (maybe + baud rate):    use a HF crystal with capacitors
                                                (cost $0.20-0.30 in qty)

real-time clock: "                              use one of above + a 32.768kHz watch
                                                "tuning fork" crystal + capacitors)
                                                (above cost + 0.20 in qty)

Of course there will always be special cases...

Best regards,
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