I like the AD844 because its internal architecture is nearly identical to what I would consider to be an excellent discrete I/V stage. It just happens to be integrated.
As for drawings, the use of the AD844 is not too different from the use of any other op-amp in an I/V stage. In my current experiment with PCM1704 DACs, the situation is simplified by the bipolar output centered at AGND.
As for drawings, the use of the AD844 is not too different from the use of any other op-amp in an I/V stage. In my current experiment with PCM1704 DACs, the situation is simplified by the bipolar output centered at AGND.
I've done further data sheed analasys of the AD844 and have already devised it's best method of implementation for diferential audio dacs.
I'll post preliminary schematics in a few hours under the topic of 'Using the AD844 with balanced current out audio DACs'...
I'll post preliminary schematics in a few hours under the topic of 'Using the AD844 with balanced current out audio DACs'...
Hi Brian
Great project! - I hope you keep updating the information on your web page as the project progresses.
Just a short comment/wondering regarding ground plane.
As I see your design, you are planning to split the ground plane directly under the DA chip into digital and analog ground.
I read an article from Ron Mancini (TI):
http://focus.ti.com/lit/an/slod006b/slod006b.pdf
who recommends keeping seperate analog and digital ground planes, but suggests that the entire DA converter should be placed on the analog ground plane (page 358).
I am slowly starting a DAC project featuring the PCM1792 chip, and was planning to keep the chip on the analog ground plane, as Ron Mancini suggests. So I was wondering what made you decide to split the ground plane under the PCM1792 and did you consider different approaches?
/Hans
Great project! - I hope you keep updating the information on your web page as the project progresses.
Just a short comment/wondering regarding ground plane.
As I see your design, you are planning to split the ground plane directly under the DA chip into digital and analog ground.
I read an article from Ron Mancini (TI):
http://focus.ti.com/lit/an/slod006b/slod006b.pdf
who recommends keeping seperate analog and digital ground planes, but suggests that the entire DA converter should be placed on the analog ground plane (page 358).
I am slowly starting a DAC project featuring the PCM1792 chip, and was planning to keep the chip on the analog ground plane, as Ron Mancini suggests. So I was wondering what made you decide to split the ground plane under the PCM1792 and did you consider different approaches?
/Hans
Not that I know anything, but this looks like a mighty good dac. I too would be interested in a couple of boards once it is ready. It would seem like a good project to start practicing soldering surface mount parts.
Great work Brian, as usual...
Sebastien
Great work Brian, as usual...
Sebastien
Multiple Grounds
is best to run the analog power ground right to the edge of the DAC. In addition, the same goes for the digital ground. Of course, if you can afford it there also should be an Analog signal ground plane.
If you doing multiple layer the digital ground should never run under and analog ground.
If you really want isolation, BB makes some great parts for isolating digital and analog ground.
is best to run the analog power ground right to the edge of the DAC. In addition, the same goes for the digital ground. Of course, if you can afford it there also should be an Analog signal ground plane.
If you doing multiple layer the digital ground should never run under and analog ground.
If you really want isolation, BB makes some great parts for isolating digital and analog ground.
Brian,
How did it worked out ? What have been your impressions on the different Dacs as shown here http://brian.darg.net/cdpro2-prototyping/cdpro2_09_dac_chips ?
I would be certainly interesed in PCBs if you have some left.
Best Regards
How did it worked out ? What have been your impressions on the different Dacs as shown here http://brian.darg.net/cdpro2-prototyping/cdpro2_09_dac_chips ?
I would be certainly interesed in PCBs if you have some left.
Best Regards
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