Actions
Forum Thread Details
  • Replies 118 replies
  • Subscribers 313 subscribers
  • Views 14016 views
  • Users 0 members are here
Related
See a helpful answer?

Be sure to click 'more' and select 'suggest as answer'!

If you're the thread creator, be sure to click 'more' then 'Verify as Answer'!

Have a question about ADCs or DACs? Ask our Expert, Nick Gray

ChristyZ

This thread has been closed to new questions.

However, we welcome you to Post Your Question about Communications in the element14 Community Wireless Communications Technology group. You'll find many fellow members and experts who have just the answer you're looking to find! 

 

Thank You, Your Friends at element14 Community


Nick Gray

 

Nicholas Gray

Nicholas has worked in the Semiconductor industry for over 30 years and has authored a number of published articles about data converters (ADCs and DACs) and signal integrity issues.

 

Parents Reply Children
  • in reply to Former Member
    Without more circuit information it is difficult to know the exact nature of the problem. However, it does seem as though you have a low value resistive load at the output. Considering that the DAC as constructed per Figure 37 of the data sheet, we find that, with a load resistor between the output and some voltage Vterm, the general form of the output is:

     

              Vout = Vterm + [ (Vref – Vterm) * Load R ] /(Rdac + Load R)

     

    where Vterm is as described above, Vref is the DAC reference voltage, Load R is the resistance of your load and Rdac is a nominal 10k, with minimum and maximum of 8k and 12k, as described in the data sheet page 16. The above formula is valid for any value of Vterm between 0V (ground) and the DAC supply voltage.

     

    The probable reasons you are seeing no output include the following:

      Your load resistance is very low, Vterm is 0V and you are measuring the voltage output to ground or output to Vterm
      Vterm is the same as Vref and you are measuring a voltage across the load or the current through the load

     

    Please know that the output voltage of this type of DAC should always be maintained at 0V to get accurate current output, which is why all of the applications in the data sheet show the use of op-amps as current-to-voltage converters.

     

    I suggest that you look at the AD5410 to source a current. It has output current ranges of 0 to 20mA, 0 to 24mA and 4 to 20mA.

     

    If you want to sink a current, I suggest you try the DAC-08. It can sink up to 4mA as long as its output is always at least 5V above its negative supply.