Electronics > Projects, Designs, and Technical Stuff

IC for function generator

(1/4) > >>

testian:
Hi,

I would like to build my own function generator. But at the moment i am not sure what chip I should use. Everything will be controlled with a microcontroller.

AD9834
AD9102
used in other projects
nearly 0 references
75MHz Clock, crystal for clock
180MHz Clock, separate clock generation necessary
Sine,Square, Triangular
Sine,Square,Sawtooth, Triangular, On-chip 4,096 x 14 bit pattern memory
0.28 Hz resolution at 75MHz
10.8 Hz resolution at 180MHz
SOP
QFN
http://www.analog.com/media/en/technical-documentation/data-sheets/AD9834.pdf
http://www.analog.com/media/en/technical-documentation/data-sheets/AD9102.pdf

For the AD9102 I could use a second, lower clock of 18MHz to get 1Hz resolution at lower frequencies.

Is the resolution of the AD9102 good enough?
Is it possible for sb. who had never done something with higher frequencies?

Thanks in advance for you answers

Kleinstein:
The AD9102 is a rather new chip - so no wonder you don't find much.
The 14 Bit resolution is quite good. The frequency resolution is still a 24 Bit word. So not that bad. Using a slower clock can work, but this would also need a second lower frequency frequency reconstruction filter.

The triangle and even more saw tooth waveform is only good for much lower frequency than the sine and ideally also wants a different reconstruction filter, though a compromise might work if you don't need the highest sine frequencies. The rectangular signal directly from the DDS ( turned NCO) is likely not useful as it would have high jitter. A good rectangular would use the sine signal followed by a comparator and maybe followed by an extra divider.

So the AD9102 can result in a much better generator: higher frequency, less distortion, extra ARB option -  though limited memory. Only frequency resolution is not that fine without changing the clock.


MarkF:
I can't tell you which to use. I built one with the AD9834 and a pic18f2550. It works well up to 1Mhz. I used a 32768Hz oscillator in order to get an exact binary division for a 1Hz output. I wish I could get the square waveform on the same pin as the sine and triangle.

Without exploring your other chip, it looks like you have a lot of additional waveforms. I think I would use the AD9102.

macck:
Hello everybody, im new to this board.

Im also into project of DDS. I've been granted samples as a student from AD and im in possesion of AD9102BCPZ and AD9833BRMZ.
I've done some research about AD9102 and it appears to be problematic (topics on AD board). Im also looking forward to learn about existing references of this one, to know-how. I've found very cool "tiny-dds" AFG with a touch screen that uses AD9834 and it's a fully open source project. I hooked on this one but i would love to replace AD9834 with AD9102 as it has RAM memory, and its capable of delivering 180MSPS  while the other generates signal driven via SPI bus from a uC and is capable of roughly 100kSPS. I'm going to study this deeper as I want to build device within 1 year for my engineering degree, it's may look like plenty of time but i think it's not :D .
Well, so im accualy into similar problem as author, but to make device somehow usefull in my workshop I would go for AD9102, and hook this up with STM32, FT801 smart display, and maybe some digital LPF's/VGA's as i recieved a lot of usefull stuff as a sample from analog/linear - but for basic coupling/offset/amplitude concept I would go for "tinydds" idea.
I would love to join discussion about designing fully functional DDS using AD9102, maybe we can work out something together with help of more experienced people on this board.

Best wishes for all of You.

testian:
I will go with the AD9834. Simply because I don't have to worry much about generating a clock signal and the better resolution. Another benefit is the better documentation.
But I will try to make it that way, that the AD9834 could be replace with an AD9102 module.

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod