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Projects, Designs, and Technical Stuff / Re: (Yet Another) DIY Multislope ADC
« Last post by Kleinstein on Today at 08:47:04 am »The run-up modulation with a 4/60 or 60/4 modulation has a usefull part of 60-4 = 56 cycles that are actually modulated. It is not just the 4 cycles that are effectively lost, but also the 4 the other polarity.
Depending on the integrator hardware 4 cycles (500 ns) for the shortest pulses and settling looks about right.
This gives the residual charge a range of about +-60 cycles range. depending on the delay between reading the comparator and the start of the feedback the range may get a little larger than just 1 feedback step. This way the run-down part could get a little larger than just -31 to + 30 counts. The range is more approximate than accurately calculted through.
A big question is how good the jitter is and if one needs / wants external synchronization to a more stable clock. Chances are the clock from the RP pico is not good enough and would at least need an external oscillator. It is not so much jitter, modulation of the crystal frequency depending on how neighboring pins are set or how much current is drawn. At the very least the pins for the ref. modulation should be away from the clock.
Depending on the integrator hardware 4 cycles (500 ns) for the shortest pulses and settling looks about right.
This gives the residual charge a range of about +-60 cycles range. depending on the delay between reading the comparator and the start of the feedback the range may get a little larger than just 1 feedback step. This way the run-down part could get a little larger than just -31 to + 30 counts. The range is more approximate than accurately calculted through.
A big question is how good the jitter is and if one needs / wants external synchronization to a more stable clock. Chances are the clock from the RP pico is not good enough and would at least need an external oscillator. It is not so much jitter, modulation of the crystal frequency depending on how neighboring pins are set or how much current is drawn. At the very least the pins for the ref. modulation should be away from the clock.