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Topic: Mismatch DAC output voltages at equal settings (Read 936 times) previous topic - next topic

SuperR

Feb 22, 2013, 03:56 pm Last Edit: Feb 22, 2013, 03:58 pm by SuperR Reason: 1
Hi,

I have a mismatch in my DAC voltage even though the values should be the same. I am having a 30-200mV mismatch. I was expecting the 12bit DAC to be awesome, but somehow it seems that the reference voltage for DAC0 and DAC1 are not the same.

Does this sound familiar and does someone know how to fix this? I tried both 8,10,12 bits, all with similar effect.

Thanks in advance.


Graynomad

Rob Gray aka the GRAYnomad www.robgray.com

SuperR

Nope, the DAC0 and DAC1 output just are not that useful. (to my application, I must add) Maybe a quickfix will solve this, but I had not found it. I eventually used dedicated DAC, "AD669"
http://www.futurlec.com/AnalogDevices/AD669ANZpr.shtml
ftp://ftp.signalogic.com/data_sheets/AD_DA_Converters/AD669.pdf

This is a "nice" one at 25 dollars, but i'm sure there are options available which are a bit wallet-friendlier.
I chose this one because of high bitdepth, Bipolar +/-10Vdc output swing and an easy to use parallel bit interace. I wrote code which made me set a value in 10uS on the Due.

I needed an ADC too and used this IC;
http://nl.rs-online.com/web/p/general-purpose-adcs/5457316/
http://cds.linear.com/docs/en/datasheet/1605fc.pdf

Again, not cheap, but is much like the AD669, but ADC instead of DAC. High bitdepth, parallel interface, bipolar +/-10V input voltage. "What else?"
I think reading is took 8 data lines, a couple of control lines, 2? and reading it took around 30 uS.


Graynomad

Thanks SuperR. That DAC looks good, you need external memory access to drive it to it's ability although it seems you are near it's limits anyway.

_____
Rob
Rob Gray aka the GRAYnomad www.robgray.com

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