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ADS1258-EP: ADS1258-EP

Sonia Vargas
Prodigy 95 points
Part Number: ADS1258-EP

It have to characterize the 24 bits ADC ADS1258-EP. It is wanted to get the best conditions for measuring DC levels with minimum noise.

From datasheet page 22 Table 4. I see that you have characterize ENOB of 21.6 bits, Noise Free resolution with 18.9 with Vref=4.096, chop=0, Delay=0, inputs shorted and 2048 sample size. I suppose fixe channel.

However, the client wants to characterize noise in auto scan mode (not fixed) with DRATE=00, DLY=111 (maximum), fclk=12.5MHz, chop=1 and from actual DC levels (not short-circuit).  Effective data rate of 420SPS. Do you think this change of conditions will increase too much the noise performance from table 4 last row (ENOB=21.6bits)?

Thanks in advance

Sonia

  • 0
    TI__Genius 14540 points
    Hi Sonia,

    The phrase "increase too much the noise performance" is relative to the performance required for a given system. I would not expect to get the same performance if inputs are not shorted. The test condition described in the datasheet is used to characterize the performance of the ADC and eliminate as many externals noise contributors as possible. By deviating from this test condition, I would not expect to reach the same performance level. Whether or not the performance level is acceptable depends on system requirements.

    Thanks
    Christian
  • 0 in reply to Christian Yots
    Prodigy 95 points
    If we make the measurement of noise instead of fclk=16MHz, DLY=000 and Chop=0 with inputs shorted but we only vary including fclk=12.5MHZ DLY=111 and chop=1 (effective data rates =420SPS). We can expect worst noise measurements than table 4 row 4 of datasheet?

    Best regards
    Sonia