The simplest design would be a serial a/d. You supply the analog input to a comparator, and then use a counter or latch to derive the bits using a dac.
When you start a conversion, set the MSB high, then check the value at the comparator. If the dac voltage is higher clear the bit otherwise leave it set and move on to the next bit. After 8 clock cycles you will have the 8 bit digital value. For the dac, the simplest thing is to make an r2r dac. It may not be accurate enough but will work. For a flash a/d you will need a resistor chain to derive the reference voltages into as many comparators as you want and a latch to capture the value. The best thing would be to grab some a/d data sheets that have simplified schematics of the internals. It will show you the pieces you need to design and then wire together. Getting accuracy from 8 bits, 3.3v supply = 12.89 mV for the LSB, analog voltage = .01289 * digital value. It will take some work to get the comparators to be accurate enough. webpages.eng.wayne.edu/cadence/ECE7570/doc/comparator.Pdf is a good example of making the comparator Ed Schram From: Nagaraj Hegde <[email protected]> Reply-To: <[email protected]> Date: Friday, November 16, 2012 1:00 PM To: <[email protected]> Subject: ADC design Hello All, Is there a place where there are some ADC design procedure in electric VLSI tool has been discussed which I can use as a starting point? I want to design an 8 bit ADC just to get some analog design experience. Please let me know! Thanks! -- --
