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DAC1280: how to send bits stream for dac1280

user6391667
Prodigy 80 points
Part Number: DAC1280
Other Parts Discussed in Thread: AMC1210, , ADS1282, DAC9881, DAC91001, DAC11001A

Dear sir 

i am curious about how many 1's or 0's data and how long  (minutes or second)

i  need to send to TDATA  in that  i can get minimum or maximum current

because in the datasheet just tell us the percent of 1's or 0's density

Thanks!!

TAI

 

  • 0
    TI__Mastermind 44550 points

    Hi TIA,

    I had to look this up because I too had the same question...

    I found these two related E2E questions and responses to be helpful in answering this topic:

    https://e2e.ti.com/support/archive/internal/int-precision_data_converters/f/75/t/95185

    https://e2e.ti.com/support/archive/internal/int-precision_data_converters/f/75/t/61405

    According Tony's response to the first link, the length of the bitstream is arbitrary, it can be as long or as short as you want to make it. In the second link, Tom links to some additional resources that may be helpful, including some MATLAB code (from https://www.ti.com/lit/zip/sbac047) which although it intended for the AMC1210, should also be somewhat relevant to the DAC1280.

    If I find out any more I'll reply back with additional information.

  • 0 in reply to Christopher Hall
    Prodigy 80 points

    Dear sir

    i can't access the link in your reply

    i have another question,if i want to get the smallest current or maximum current 

    what can i do? in the datasheet it  only tell us just  calculate the 1 and 0 density

    but we don't know how long dac will stop calculate the 1 and 0 density (update rate)

    ,we need to send 2^24 data??

    thanks!!

  • 0 in reply to user6391667
    TI__Mastermind 44550 points

    Hi TAI,

    If you'll refer to the following diagram, there are multiple flip-flops in series which control a total of 19 current taps. If you clock in alternating "1"s and "0"s on TDATA, you'll get a differential output current of nearly 0 mA. Therefore, the minimum output current will require clocking in 0101010...

    For the maximum output current, you only need to clock in a signal of 75% "1"s density, so for example 01110111...

    For anything in between, the flip-flops will perform a moving average on the bitstream to calculate an average output current.

  • 0 in reply to Christopher Hall
    Prodigy 80 points

    Dear sir

    it's more clearly!! but could you please give me the other  current  pattern

    for example  6%, 43% .the other question is if  i want  to achieve 24bits dac 

    accuracy , more 1 and 0  will be sent to the dac moving average  D flip flop??

    and  i need to repeat send the pattern??

    many thanks!!

    TAI

        

  • 0 in reply to user6391667
    TI__Mastermind 44550 points

    Hi TAI,

    Take a look at the AMC1210 MATLAB Code I referenced above. It has a script that should help with generating bitstreams.

    Note the DAC1280 is not really a 24-bit DC accurate device. I know the TI.com parametrics show it as being a 24-bit DAC, but nowhere in the datasheet is resolution actually specified. This device is really a low THD DAC that is intended to be used with the ADS128x devices and filtered by a digital filter. If you not filtering the DAC output with the ADS1282 digital filter, for example, you'll see a lot of in-band noise.

    If low-noise and high-accuracy are important, then I'd recommend one of these devices instead: DAC11001A, DAC91001, or DAC9881.