Flash A/D error

I don't see it, it looks OK to me.

The top comparitor is to measure the overvoltage condition, which is mentioned in the text.

Or are you refering to somewhere else in the text? To correct the text we need to pin it down.

 

They don't mention the top comparator specifically, but it does the same job. If the input voltage exceeds Vref then the 8th digit is on, the maximum number. Binary 000 - 111, which is eight permutations. Matches 8 comparators nicely.

 

So how are you going to get 111 if you eliminate the top comparator? 8 possible numbers, 000-111, require 8 inputs. You can not have 000-111 with 7 inputs, it becomes either 001-111 or 000-110.

Is the assumption if they are all zero then you have 000? I'm thinking of a mirror to the CD4512.

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OK, I can see it. The author was making the same assumption I was, 8 inputs required for a mod3 output. This section is going to require a complete rewrite, I think.

What he is showing is valid, but you can remove one comparator with the assumption of all zeros in equal all zeros out. Since removal of a component is more or less industry standard, I can see the confusion.

 

Another thing, look at the first 2 pictures, compared to the 3rd. It is correct on the 3rd illustration. Good catch.