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ADS7808 remplaced by ADS8508 to DAC8043

xavier munger
Prodigy 70 points
Other Parts Discussed in Thread: ADS7808, DAC8043, ADS8508, ADS8509, DAC8811

Hello,

I have a probleme and i need your help :

I have 2 circuit with different alimentation (for isolation) i have to send a signal from the first circuit 0-10V to the second. I made that with the ADS7808 and on the second card i convert the signal with a DAC8043, this is working well.

My probleme is that the ads7808 is not made anymore, when i replace the ADS7808 by the recomended one ADS8508 my system is not working cause the DataClk cycle on the ADS8508 is 110ns and on the DAC8043 the DataClk minimum is 210ns !

I need a solution for fix this probleme ! Change the ADS8508 or the DAC8043 ?

 

Thanks for your help !

 

Best regard

Xavier Munger

  • 0
    TI__Mastermind 46290 points

    Xavier,

    Can you elaborate on the system/problem a bit? Do you have a micro-controller communicating to the ADS8508 and DAC8043? Are they on the same SPI bus?

    The ADS8508 data clock cycle is 110ns if you use the internal clock. If you've got a micro communicating to both devices on the same SPI bus and you don't want to change clocks between communicating you could use the external clock mode on the ADS8508 where the minimum clock cycle is 30ns. You'd run the SPI bus at 210ns clock cycle and be able to communicate with both devices without changing your clock.

    I might be missing some details here...hopefully you can describe the system some more.

  • 0 in reply to Kevin Duke
    Prodigy 70 points

    Hello

    i dont know why but the system is not working really good ! some times i cant post! 

     

    I don't have a micro on my circuit! i give you the schema where it wase working i think it's better for understand! 

     

    http://www.flickr.com/photos/69327197@N05/6304977825/

     

    let me know if you have any question .

     

    thank you for your great support!

  • 0 in reply to xavier munger
    TI__Mastermind 46290 points

    Xavier,

    I apologize for the delay, I didn't get any notification that you responded to the post with your schematic. I was suspect that you might be doing something like this...let me look around and see if we can find a good solution.

  • 0 in reply to Kevin Duke
    TI__Mastermind 46290 points

    Xavier,

    A good 12-bit solution hasn't really jumped out at me just yet. The real trick is just finding an ADC and DAC that both have simple interfaces so they can match up well with each other like you had with the previous combination. We looked into doing something similar with another customer in the past, but that design used 16 bits of resolution. Is moving up to 16 bits something you can give consideration to in this design?

    If so take a look at the ADS8509 + DAC8811. The DAC8811 is very similar to the DAC8043 and the ADS8509 is of the same family as the ADS8508.

  • 0 in reply to Kevin Duke
    Prodigy 70 points

    Kevin,

    Thank you for your support! i can use 16bit resolution! without probleme! the solution you prupose look fine for me ! 

    i would like to know if its possible to have couple sample of both IC for make some try!? 

     

    Thank a lot!

  • 0 in reply to xavier munger
    TI__Mastermind 46290 points

    Xavier,

    Both of the product folders for these devices should have an option for you to sample. It'll look something like this;