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ADS8166: AVDD - DVDD power domains and minimum consumption

Nicola Cellurale
Intellectual 1170 points
Part Number: ADS8166

Dear PADC Team,

i have a couple of questions regarding ADS8166 that my customer is designing on his application:

- I see that AVDD and DVDD belong to independent power domains, in the application there may be scenarios without AVDD and DVDD still present: no issues if AVDD goes below 0.7 and after the AVDD power up a reset is issued correct?

- regarding IVDD consumption, do we have a number at 1.8V w.r.t. 0.45uA @3V?

Thanks for your support

Nicola

  • 0
    TI__Mastermind 36190 points

    Hello Nicola,

    Yes, not issue as long as AVDD falls below 0.7V and then monotonously rises back up to at least 3V with external reference (or 4.5V when using the internal reference).  You can get the device into an undefined state if AVDD rises above 0.7V but then decreases before reaching the minimum of 3V (or 4.5V).  

    I will need to check with the design team to see if we have data at 1.8V for IVDD.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • 0 in reply to Keith Nicholas
    TI__Expert 3675 points

    Hi Nicola,

    Regarding Idvdd, it is important to note that the datasheet spec is with 'no conversion'. Hence SDO is not switching. In this case the device will only draw leakage current from DVDD. To answer the customer's question, we will have to calculate the current as: C*V*F.

    Where:

    C = capacitive load on SDO

    V = DVDD voltage

    F = 16bits x (sampling rate of the ADC)

    The capacitive load on SDO (typically 10pF) must be charged 16 times for 16bit data in every data read cycle. Hence the average current consumption from DVDD rail will be:

    Idvdd = 10pF x 1.8V x (250kHz * 16bits)

    Idvdd = 72 uA

    I hope this helps.

  • 0 in reply to RahulVK
    TI__Intellectual 1170 points

    Hi Rahul,

    thanks a lot, clear. do you maybe have an estimation of IVDD in case of no conversion (no AVDD even) when the device is let's say in idle mode?

    Any data on the leakage on VDD at 1.8V?


    Thanks a lot

    Nicola

  • 0 in reply to Nicola Cellurale
    TI__Expert 3675 points

    Hi Nicola,

    We do not have data for Idvdd with 'no conversion' at 1.8V in the datasheet. However, the Idvdd at at 1.8V with  'no conversion' will be less than 0.45uA.

    A coarse estimate can be made as follows:

    Idvdd (no conversion) = 0.45uA * (1.8V / 3V)

    Idvdd (no conversion) = 0.27uA

    Does his help?