ADS8028: Temp sensor output value error at electromagnetic field immunity test

Hello Muk,

1. We do not have information about how the temperature sensor will behave under EMF. But when you say unstable, are the readings completely wrong? or is there a shift. How exactly is it unstable? does it behave as expected at other temperatures outside of 20C to 60C?

Overall, we suggest using good shielding and coupling at the power supplies.

2. Below is a timing diagram of configuring and reading out the Temp sensor data.

The Control Register needs to be set for the temperature sensor to convert, this is the first frame

The second frame, when BUSY is high, this indicates that temp sensor data is being converted, but the data will not be outputted until the next frame when BUSY is then low, the third frame.

Regards

Cynthia

Hi Cynthia-san,

Please refer the following read values gruff.

It seems random. 

 X : measurement times(F=around 4sec), Y : Temp sensor read value *C

It was measured by room temp. but ADS8028 is sealed inside their system.

Sometimes, the read result become over 75C. then, their test was Fail. 

Also, in case of normal situation (not EMF), then, it was no problem. 

As your mention, we should suggest using good shielding and coupling at the power supplies.

Do you have any idea for specific method of the shielding and coupling at the power supplies? Could you please let me know it.

By the way, the read values between AIN0 and AIN7 are no problem. Are temperature sensors susceptible to noise?

(Additional question)

Conversion time for  AINx is 700ns

Conversion time for  Temp sensor is 100us

Could you please let me know the reason of difference between AINx and Temp sensor?

Customer want to know the Temp sensor's internal mechanism and sequence. 

Thanks

Muk

Could you please help my questions?

Hello,

Apologies for the delay due to holidays. I am reaching out to our design team to get more information about the internal temp sensor.

Until their response, I will not be able to say if the temp sensor is more susceptible to EMF, and if so how.

Since it is completely internal, it will be hard to compensate. Firstly I would suggest large solid ground planes and well sized decoupling caps on the power supplies.

From there, shielding can look different based on the application. one can add a physical cover over the device on the PCB, shielding cable can be used, and such.  If you would like to speak about this in further detail, feel free to email me.

Regards

Cynthia

Hi Cynthia-san,

Thank you for your response.

I wait the design team feedback.

Thanks

Muk