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ADS114S08B: REFCOM connection

Part Number: ADS114S08B

Hello.

We are going to use bipolar supply in system: AVDD = +2.7V, AVSS = -2.7V.

We want to connect REFCOM pin to GND = 0V.

Absolute maximum ratings for REFCOM from datasheet do allow such kind of topology,

but in "Pin Functions" table we can see a strict directive: "Negative voltage reference output. Connect to AVSS."

So the question is: can we connect REFCOM pin not to AVSS, but to the middle point between AVDD and AVSS?

  • Hi Slava,

    The Absolute Maximum Ratings do not ensure proper operation for the ADS114S08B, but only that the device will not be damaged.  See the note under the table in the datasheet.  Setting the supply voltages to +/-2.7V is beyond the Recommended Operating Conditions and very close to the Absolute Maximum of 5.5V for AVDD-AVSS.  Any instability of the supplies could exceed the absolute maximum and damage the device.

    The internal reference is designed to operate, or in other words establish a stable regulated output, by setting the REFCOM to AVSS.  If REFCOM is connected to some other voltage point not AVSS, the reference will start to oscillate.  So REFCOM must connect to AVSS if the internal reference is to be used.  Just to be clear, the reference output is still 2.5V relative to AVSS even though when measured to AGND may appear as 0V (AVSS=-2.5V) or -0.2V (AVSS = -2.7V).

    Again I wish to emphasize that the system should not be designed for normal operation using the values in the Absolute Maximum Ratings table, but instead the table for Recommended Operating Conditions.  The Absolute Maximum Ratings are to be used to make sure that the design never exceeds the ratings which can damage the device.

    Best regards,

    Bob B