Here is the digital cousin to the analog ramp type ADC: The Counter Analog to Digital Converter/Digital Volt Meter.
One big plus to this design is that the output number is independent of the frequency of the clock, unlike the analog ramp ADC. So, I can use a speed clock where frequency is undetermined.
If you look very closely, you might be able to see that the ramp voltage appears to have a serrated edge. (If you can't, delete the sine wave test voltage, pause simulation, and zoom in on the time scale) That's because it is made of tiny steps (like a long stair case), which is caused by the digital feedback from the counters changing back into analog.
If you're confused about what I just said, hopefully, my previous counter digital voltmeter tutorial will help. https://everycircuit.com/circuit/4509930926899200
This circuit illustrates why having a sample-and-hold circuit is a good idea. Note how when the sine input voltage rises, the counters keep trying to follow it, and that messes up the reading. Having the voltage change during a sample measurement can lead to inaccuracies.
Specifications:
Sample rate: ~19ms or 52 samples per second.
Accuracy: 100mV
Error: ~100mV
Range 0V to 9.9V
OUTPUT NUMBER ~ BCD number on counters
If 6V is input, then it will count ~0110 0000 = 60
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