| Author |
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Frank
Guest
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 Posted:
Mon Nov 28, 2005 9:15 am Post subject:
AD9218, what will the negative values be in binary mode? |
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When my DAC output is from 0-1V, and is fed into 10-bit AD9218 which
is set to binary mode, what binary value will I get when the input is -10mV? |
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PeteS
Guest
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| Posted:
Mon Nov 28, 2005 9:15 am Post subject:
Re: AD9218, what will the negative values be in binary mode? |
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further to my other reply, if you are using offset binary, then you
will get N[off] - 10 (decimal). The output of the DAC at Vin(centre)
should be 0x200, so you would get 1F6.
Cheers
PeteS |
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PeteS
Guest
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| Posted:
Mon Nov 28, 2005 9:15 am Post subject:
Re: AD9218, what will the negative values be in binary mode? |
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I assume you mean -10mV AC coupled into the AD9218 (it is internally
biased at 1/3Vdd)
You would have 1/200 of the negative dynamic range, or 1/100 of the
span range which gives -10/1024.
As the output is set for 2s complement, the output will run from +511
to -512 (Hex = 0x1FF at +511 to 0x200 at -512) for an input of 1Vp-p,
so in this case, you should get 3F6, rounded to the nearest integer.
(-10 decimal)
Cheers
PeteS |
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Von Heler
Guest
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| Posted:
Mon Nov 28, 2005 3:37 pm Post subject:
Re: AD9218, what will the negative values be in binary mode? |
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On 28 Nov 2005, Frank put down his happy meal and blurted:
| Quote: | When my DAC output is from 0-1V, and is fed into 10-bit AD9218 which
is set to binary mode, what binary value will I get when the input is
-10mV?
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I'm lovin' it. |
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Jerry Avins
Guest
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| Posted:
Mon Nov 28, 2005 5:15 pm Post subject:
Re: AD9218, what will the negative values be in binary mode? |
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Frank wrote:
| Quote: | When my DAC output is from 0-1V, and is fed into 10-bit AD9218 which
is set to binary mode, what binary value will I get when the input is -10mV?
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If your DAC is really set to produce outputs from 0-1V, any apparent
negative voltages are necessarily analog noise. This isn't a question
about bit values.
There are straight binary, offset binary, and two's-complement binary.
If you want details, point me to relevant data sheets.
Jerry
--
Engineering is the art of making what you want from things you can get.
ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ |
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Frank
Guest
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| Posted:
Mon Nov 28, 2005 5:15 pm Post subject:
Re: AD9218, what will the negative values be in binary mode? |
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Thank you Peter.
My digital output is from 0-1024 (1MHz sine wave 0 -> -1, 1024 -> +1) and
fed into the
10 MSBs of DAC (TI DAC290x-EVM). Due to noise, the DAC has some below zero
values on oscilloscope (-20mV ~ 0.8V). When I connected this signal to ADC,
how do I
ensure that the digital output is the same (or nearly the same) value of my
original digital input?
(The requirement is such that after I captured the ADC O/P with logic
analyzer, plotted in
graph of 0~1024, it shows a sine wave without bad codes).
"PeteS" <ps@fleetwoodmobile.com> wrote in message
news:1133167821.286103.231790@f14g2000cwb.googlegroups.com...
| Quote: | further to my other reply, if you are using offset binary, then you
will get N[off] - 10 (decimal). The output of the DAC at Vin(centre)
should be 0x200, so you would get 1F6.
Cheers
PeteS
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