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ADS1247 GPIO Output Level (Bipoiar Analog Power)

cafain
Mastermind 6755 points
Other Parts Discussed in Thread: ADS1247, ADS1248

Hi,

ADS1247 About voltage value of the GPIO output when using a Bipolar power.

Will be used in AVDD = +2.5V and AVSS = -2.5V.
When you use the analog power a Bipolar power, or the output of the GPIO is negative voltage is output?
How many GPIO output voltage value?

Data sheet (page4) is written with the VOH = 0.8AVDD and VOL = 0.2AVDD,
however, on page30 is
 "When the ADS1247/8 are operated with bipolar analog supplies, the GPIO outputs bipolar Voltage.
It has been written.

Which is correct?


Best regards

  • 0
    TI__Guru* 97465 points
    Cafain,


    The Electrical Characteristics on page 4 describe when the device is operated with a unipolar supply.

    The GPIO is directly powered with the analog supplies and runs from AVSS to AVDD. Therefore, you would expect the GPIO low level to be near AVSS, and the GPIO high level to be near AVDD.

    Using the input GPIO levels:
    VIH would be between 0.7*(AVDD-AVSS)+AVSS and AVDD, and
    VIL would be between AVSS and 0.3*(AVDD-AVSS)+AVSS
    For AVDD=2.5V and AVSS=-2.5V, VIH=1V, and VIL=-1V.

    Using the output GPIO levels:
    VOH would be between 0.8*(AVDD-AVSS)+AVSS and AVDD, and
    VOL would be between AVSS and 0.2*(AVDD-AVSS)+AVSS
    For AVDD=2.5V and AVSS=-2.5V, VOH=1.5V, and VOL=-1.5V.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Mastermind 6755 points

    Hi,

    Thanks to immediate answer.

    That GPIO output to the negative side, I understand.
    The contents of this answer content and data sheet is considered to be different.

    You think it is necessary to data sheet of the modification, do you have that plan?

    Best regards

  • 0 in reply to cafain
    TI__Guru* 97465 points
    Cafain,


    We are in the process of a revision of the ADS1248 and we will consider the change in the GPIO input and output levels. As I mentioned earlier, the original wording was meant to show levels for unipolar analog supplies, but we could write it to include bipolar supplies.


    Joseph Wu