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ADS114S08B: About power supply

Junya Kato
Expert 1635 points
Part Number: ADS114S08B


Hello Team,

1) Is there any problem with the operation below?

- DVCC,IOVDDA : Always supply 3.3V
- AVDD : supply 3.3V when during operation, and 0V when stopping operation


2) When power is supplied as below, is it no problem if the same voltage as DVDD or IOVDD is input to the digital pin(CS,DIN,SCLK,DOUT,DRDY,CLK,START/SYNC)?

- DVCC,IOVDDA : 3.3V
- AVDD : 0V

Best regards,
Kato

  • 0
    TI__Guru** 113765 points
    Hi Kato-san,

    It is ok to turn off the AVDD power as long as the Absolute Maximum Ratings for the analog inputs are not exceeded (section 7.1 on page 5 of the ADS114S08B datasheet.) Care must be taken when removing power as some external devices can have capacitors that will discharge slower on the analog (or reference) inputs than the AVDD supply exceeding the absolute maximum.

    When AVDD goes to 0V, the device will be held in a reset condition until the AVDD supply has exceeded the POR threshold (approximately 1.65V.) At this time the registers will be reset to initial values and must be written with the appropriate contents for the desired operation as previous settings will be lost.

    It is possible to apply voltages on the digital pins when AVDD is 0V, but the device will not respond while being held in a reset condition.

    Depending on the duration that AVDD is 0V, it may not save as much power as you might think by switching off the AVDD as a lot of charge is lost on capacitors connected to the analog portion that will need time to recharge once depleted. There are a number of ways of limiting current to the analog portion by running the analog in power-down mode and either using the low-side switch of the ADS114S08B to shutoff sensor current, or using another external switch for sensors.

    Best regards,
    Bob B