es9018 current mode question

Thread Starter

coinmaster

Joined Dec 24, 2015
502
Hi, I'm building an output stage for an es9108 dac running it in current mode by running it into a virtual ground but I have a question about the offset voltage of the virtual ground. Should I have the virtual ground run at 1/2 the dac supply voltage or is it okay if I run it at 0v?
 

Papabravo

Joined Feb 24, 2006
13,459
IIRC the DAC has differential current outputs and offset voltage is generally not a problem if the amplifiers have a bipolar supply and the output is with in the common mode range.
 

Thread Starter

coinmaster

Joined Dec 24, 2015
502
The output stage is bipolar, I'm just not sure if the dac can achieve it's full dynamic range of current into 0v since it does not have a negative supply.
 

Thread Starter

coinmaster

Joined Dec 24, 2015
502
In the datasheet I found this
Differential current output is equivalent to a differential voltage source in series with a 781.25Ω
resistor. The differential voltage source has a peak-to-peak output range of 3.05V (0.924*AVCC)
and an output offset of 1.65V (AVCC/2).
So, that basically means it can work into 0v but there will be a DC current offset if I don't set the virtual ground to 1.65v right?
 

Papabravo

Joined Feb 24, 2006
13,459
In the application circuits at the end of the datasheet there is a node that is referenced as "Vcm". I wasn't thinking about this in terms of an offset, but it may be. I was thinking in terms of the intrinsic offset voltage of an opamp that is required to get the output to be zero.
 
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