# 4-bit successive approximation

#### kaznov

Joined Mar 10, 2012
30
guys how I would use the plot attached for a 5 bit converter if the input signal is 2.25 V and the input range is from -5 to +5 V

I know that I would divide the 5 bit segmants to 1/2, 1/4, 1/8, 1/16 and 1/32 respectively and I know that if I get a value higher than 2.25 would correspond to 0 and if lower than 2.25 would giive me 1 in term of digital code , but how would i calculate !

#### t_n_k

Joined Mar 6, 2009
5,455
Hello kaznov,

Your threads look more like homework problems than material for electronic chats. It might be construed as "deceptive" and ultimately prove unhelpful to you if this really is homework. Start your threads on the Homework Forum if this is true. Keep in mind that conditions apply for help with homework.

Regards,

t_n_k

#### jegues

Joined Sep 13, 2010
733
guys how I would use the plot attached for a 5 bit converter if the input signal is 2.25 V and the input range is from -5 to +5 V

I know that I would divide the 5 bit segmants to 1/2, 1/4, 1/8, 1/16 and 1/32 respectively and I know that if I get a value higher than 2.25 would correspond to 0 and if lower than 2.25 would giive me 1 in term of digital code , but how would i calculate !
You question isn't very clear, so I'll just give you some general information of successive approximation.

So if you want to use say a 5 bit converter, your first guess should be in the middle of the range. (i.e. 10000)

The next thing you do is compare your guess to the analog value you are trying to convert.

If your guess is to low, you make your guess higher, like so,

11000

01000

And this is done until all 5 bits have been determined.

This adding and clearing of individual bits within the 5 bit string can be done with OR and XOR statements in conjunction with a comparator comapring the analog signal you wish to convert. This can all be accomplished within software (aside from the comparator) if you are using say a MCU to do the conversion.

If not, I'm sure there is a way you can achieve the same result using hardware.

Hope this helps,

Cheers!

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