Re: Si5351 audio pops and PLL Lockups
Dave Benson
Ron- Without knowing what's in your firmware, I'll comment on those bypass caps to ground at the encoder. When the contacts are in the 'open' state, the caps are being charged to 5V through a pullup resistor. When the contacts close, though, the charge on the caps is discharged to ground at a pretty high instantaneous current. That's a source of unwanted noise. It can be remedied by adding a fairly low resistance (say, 100 ohms) in series from the caps to the encoder contacts. If you're using a high-resolution encoder, there's an off chance you're generating frequency updates faster than the Si5351 can accept them. Not sure what it would do then. My recollection is that the updates take 5-10 milliseconds. It may also help to command the Si5351 outputs 'off' prior to any update and restore them only after the command sequence is complete. I was working with an earlier version of NT7S's library, though, and haven't kept current on newer library versions. 73- Dave, K1SWL
On Tue, Mar 17, 2020 at 9:09 AM WB9YZU via Groups.Io <wb9yzu=yahoo.com@groups.io> wrote: Hi Folks, I'm sure you folks have fielded this question before, but search results haven't been very fruitful.
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