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Information about ADC's

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ethan169

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So im a little confused about ADC's (A to D converters) and unfortunatly this is becasue i probobly didnt pay much attention to this topic when i was in school. If only i could go back....Anyway

Im working witha AD9271 and trying to modify some VHDL code in a Xlinx FPGA that will communicate with this new chip.

I guess my first question is does anybody have a site or some place or even a few words that can help me understand how an ADC works?

Second Im looking through the data sheets for the AD9271 and im trying to understand the defaults of the device. As in upon power up what is the default state etc.

Here is the link for the data sheet on this AD9271http://www.analog.com/static/imported-files/data_sheets/AD9271.pdf

On page 9 are the ADC timing diagrams and page 38 has table 15 wich is the memory map register. In table 15 is a column named "Default Value" Im having trouble understanding this as well.

Any information would be much appreciated.

Thanks!
 

dknguyen

Well-Known Member
Most Helpful Member
How the ADC works depends on the the type of ADC you are using.

What are you having trouble about for table 15? It tells you the initial state of the registers on power-up or reset.

That is one heavy, hard-hitting datasheet though.
 
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ethan169

New Member
How the ADC works depends on the the type of ADC you are using.

What are you having trouble about for table 15? It tells you the initial state of the registers on power-up or reset.

That is one heavy, hard-hitting datasheet though.
I agree this data sheet is extremely thick and has tons of information. The data sheet for the ADC that was previously used is about 1/4 of the size of this one.

I guess what i was confused on was the default value but after a second look it seems that the X is a dont care and the rest is HEX?

-Ethan
 

crutschow

Well-Known Member
Most Helpful Member
In simple terms an A/D converter samples an input analog signal and converts the value into a digital word at a sample rated determined by the particular A/D used and its clock rate. The sample rate has to be greater than 2 times the maximum analog signal frequency to avoid aliasing (generation of false sample words).

The device your are using is a specialized device designed for high speed, multiple channel applications such as medical/ultrasound imaging and doppler radar. It's a complex device and far from trivial to use. It includes an amplifier and anti-alias filter for each channel.

It will take much careful and time-consuming analysis of the data sheet to determine how to use the chip. If you have specific questions about its operation, perhaps someone can help you there. Just to say you don't understand a timing diagram, a memory map register, or a "Default Value" column is a little too general a question.
 
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ethan169

New Member
In simple terms an A/D converter samples an input analog signal and converts the value into a digital word at a sample rated determined by the particular A/D used and its clock rate. The sample rate has to be greater than 2 times the maximum analog signal frequency to avoid aliasing (generation of false sample words).

The device your are using is a specialized device designed for high speed, multiple channel applications such as medical/ultrasound imaging and doppler radar. It's a complex device and far from trivial to use. It includes an amplifier and anti-alias filter for each channel.

It will take much careful and time-consuming analysis of the data sheet to determine how to use the chip. If you have specific questions about its operation, perhaps someone can help you there. Just to say you don't understand a timing diagram, a memory map register, or a "Default Value" column is a little too general a question.

I agree. I didn't say that I was programing the entire FPGA. Only attempting to modify the section the deals with this from a previous ADC. I am in a little over my head that's for sure. But im trying to learn and take it one step at a time. I appreciate your comments though. I guess i was getting overwhelmed and asked a generic question.

Ill work on this a little more and get back to you if I have any more specific questions.

Thank you!

-Ethan
 

dknguyen

Well-Known Member
Most Helpful Member
I agree this data sheet is extremely thick and has tons of information. The data sheet for the ADC that was previously used is about 1/4 of the size of this one.

I guess what i was confused on was the default value but after a second look it seems that the X is a dont care and the rest is HEX?

-Ethan
Yeah, X is don't care or no value...in either case, if you need it give it an explicit value.
 
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