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ADS1220: ADC to assemble pressure and temperature sensor

Jonathan Navor
Expert 7805 points
Part Number: ADS1220

Hi Experts,

Good day! I am posting this on behalf of the customer. 

I use ADS1220 as ADC to assemble pressure and temperature sensor. For cost saving, I use an internal temperature sensor as a temperature source and use a MEMS bridge to generate pressure signals.

After calibrated pressure,  The accuracy is OK. But the temperature signal has a bigger error based on the datasheet specification 0.5℃. When the ambient temperature is above 10℃, the accuracy is good. Below 0℃, for example, -20℃, the error is about 3℃. It seems I need to calibrate the internal temperature sensor. Do you think the internal temperature signal is abnormal?

I want to have some test data so I can estimate multi-order fitting. Can you provide me? Or do you think linear fitting? third order fitting or even more? Even Segmental fitting?

Thank you in advance for your support. 

Best regards,

Jonathan

  • 0
    TI__Mastermind 35470 points

    Hi Jonathan,

    The accuracy of internal temperature sensor should be in the range of -1°C ~ +1°C at the TA = -40°C to +125°C. The accuracy graph has been shown in the following figure in the data sheet:

    Best regards,

    Dale 

  • 0 in reply to Dale Li
    TI__Mastermind 35470 points

    Hi Jonathan,

    I had a communication with an expert in our team. Please see the following analysis and suggestion from him:

    The problem with using the temperature sensor and achieving 0.5 (or even 1) degree C accuracy is the die temp does not necessarily equal the ambient temp.  The part is validated in an oil bath where the oil surrounds the chip and the temperature of the chip/die is very close to the oil bath temp. 

    In a system test, the ambient air temperature can easily be different than the die temp.  This will be very noticeable at colder ambient temps as current running through the ADS1220 will create some self-heating.  For the system test most likely a considerable soak time will be required before the die will approach the ambient.

    I hope this helps.

    Best regards,

    Dale