How does glitch happen in ad/da design & how to decrease

[tuza2000]

ad da gray code

glitch are usually important for the performance specification of d/a converter,but how about to a/d converter?
i found glitch in the output of adc giving a large decrease of the signal-to-noise ratio.
how does the glitch happen?
and how to decrease it?

thx your help!

 

[everton]

Re: glitch in ad/da design

Is there a synchronous clock at the output of ADC to make sure data are captured at the right time?

Sometimes these glitches could be due to the internal circuitry still trying to make a "final output decision", but the transients showed up as glitches due to differences in delay among the gates.

 

[tuza2000]

glitch in ad/da design

i can't understand what you mean everton,i have a clock in outbuffer,i found that the glitch due to different delay among the gatesm
how to control the delays of the msb and lsb?
i make all the output coder rom the same size transistor,is it necessary to make different size by different bit?

 

[ocarnu]

Re: glitch in ad/da design

That is called bit syncronizaton. What kind of ADC is that? AFAIK appears only in folding ADC.
Use Gray code and you get rid of it. Or some additional hardware.

 

[tuza2000]

glitch in ad/da design

my design is flash architecture,
i want to use Gray code but there are two problem that i dont know how to resolve:
first is how to convert the gray code output to bcd code inorter to envalue the performance of my design ?
second is that is it necessary to design a Gray code to BCD code circuit in the design ?or i can do it use matlab after apture the output to pc?

and d/a converter treat the glitch as noise,
how about a/d converter?

 

[ocarnu]

Re: glitch in ad/da design

If you have flash, you use thermometre code. There is no reason to use gray, becuase th. code and gray have the same property: 1 lsb chnage means only one bit change in the code.
Actually, I don't understand why you these code at the output: I see on you pictures a code 31+1+1.4 or smth like this.... how do you get 33.4 code? In 6 bits? What is the digital output? 6 bits= 0->63 and this is it.

 

[tuza2000]

glitch in ad/da design

tocarnu

the 33.4 code is the result of the glitch ,when 47 ->49,"32 +1 "does change and "8+4+2" change to 0 firstly,just before "16" become true, so there is a period that no "8+4+2" and "16".

i want to use gray code because of the decrease of the glitch like that.

the thermometre code was produced by the comparator and should be turnde to 6 bit code.