Bob wrote:
I hadn't given any thought to correcting the linearity of the TIC I built, but my PLL plots tell me I should do it now.
You are using a resistor to charge the integrating capacitance, so it charges with the classic exponential curve and you get a nonlinear time-to-voltage conversion. You need to charge the integrating capacitance with a constant current if you want a linear time-to-voltage function. The current source will probably need to be connected to a supply that is higher than 5v, because it needs some headroom.
There may be secondary errors, as well, due to the leakage of the tri-state buffers in their hi-Z state and/or nonlinearity in the ADC's internal capacitors. Often you can improve things by using sufficient external capacitance to swamp the ADC's internal capacitance and increasing the charging current.
Best regards, Charles _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
