ADS8668:Regarding the standard circuit

Hi Rina! 

Welcome to our e2e forum!  Please post your query in English!

We are currently considering using your product "ADS8668" in a project under development. We are considering using this component in the AD conversion circuit for temperature sensor input. In this case, is there a standard circuit available? Although there was a description of the standard circuit for power automation/PLC in section 9.2 of the datasheet, would it not be applicable in this case?

Hi Rina,

Thank you for re-posting!  What temperature sensor are you using?  The ADS8668 has a 1M input impedance, so it might not be the best choice depending on your sensor selection.

We are using various temperature sensors such as "SEMITEC 202AT-11". As for the analog input circuit, we envision a circuit where the resistance value of the temperature sensor is input to the ADC via an operational amplifier, and the result of the AD conversion is output to the CPU.

Sounds interesting!  Here is an app note that you can review as one means to accomplish the task.  You can also use an amplifier with gain and/or offset if needed depending on the intended temperature range you are measureing and the input voltage range that you intend to use on the ADS8668..

So, the application note can be considered as one of the means to execute the task, right? Regardless of the circuit in which the ADC is used, is the circuit described in section 8.3.8.1 necessary when using the built-in reference power supply? Are there any other necessary circuits or pin configurations?

As noted in 8.3.8.1, if you intend to use the internal reference, you should buffer it off of the REFIO pin.  In the app note I pointed you to, AVdd is the reference for that particular ADC.