8-bit tracking ADC

Thread Starter


Joined Dec 29, 2005
I have a task to design the cicuit for an 8-bit tracking Analog-to-Digital converter, the list of IC's we are suppose to use is:

74LS191 4-bit up/down Counter
LM311 Voltage Comparator
AD558 8-bit DAC

What i dont understand is, is it possible to create an 8 bit ADC converter using a 4-bit counter and if so how should the counter outputs be connected to the 8bit DAC inputs, or could we be supposed to use two 4-bit u/d counters if this is the case how should the 2 counters be linked together?
i'd appreciate any thoughts you all might have.



Joined Apr 20, 2004

I think you'll need more logic to make the ADC. The 191's (you will need two of them) will count up or down until the comparator changes state, indicating the voltages match. The count in the 191's will be the digital equivalent of the analog input. The datasheet on the 191 will show you how to connect them so the counts carry through.

You will need some control logic that can count the 191's up or down to match the input voltage. It can be done stand-alone, or with a microprocessor.
hi may be i am new uer but i think i got the answer

u should cascade the two 4-bit counter by using a top count pin of one counter as a input to the clk pin of second counter or u should just GND first or last four I/P pin of the
ADC & go with single 4 bit counter .


Joined Jan 23, 2006

When designing circuits, I often found valuable help by going to the component manufacturer's web site and searching for application notes on the component I wanted to use.

The data sheet will give you the component specifications. The application notes discuss designing with that component.