the questions about MPC5642A eQADC measurement error

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the questions about MPC5642A eQADC measurement error

336 Views
enwei
NXP Employee
NXP Employee

Hi,

 

one of my customer is using MPC5642A to develop BMS products, the project is going to SOP in Q2 of 2016, and now they met the issue of ADC measure error. Their system requires the MPC5642A to meet total 10mV error. After onsite discuss with the customer and they still have the following questions/confusions:

 

1. Whether the TUE8 and TUE16(Table 28. eQADC single ended conversion specifications (operating)) in our spec of MPC5642A datasheet(MPC5642A Microcontroller Data Sheet, Rev. 3.2, 12/2014) has considered the effect of temperature? If not, what’s the relationship? If yes, whether it always meet the spec in -40 to 125 degree?

 

2.The TUE8 is min -4 counts and max +4 counts, what’s the probability of each error grade, can we give out the  probability curve? For example, there are 80% probability to get 0 count TUE and 1% probability to get +4 count TUE and etc.

 

3.whether the TUE contains the error caused by the external ADC reference voltage(Power Supply Noise Error)? The AN2438 ― ADC Definitions and Specifications, J. Feddeler and Bill Lucas says :

 

Total Unadjusted Error (ETUE) ― The difference between the Actual Transfer Function and the Ideal Straight-Line Transfer Function; includes all forms of error.”

 

If not, and the customer can only buy the reference voltage regulator(ADR02ARWZ) with best 8.36mV accuracy at present, can it meet their system target total10mV measurement error when works with our MPC5642A?

 

Or can you recommend a higher accuracy reference voltage regulator or SW solution for the customer?

 

Please forward this questions to AE of MPC5642A and look forwards to your timely reply.

 

 

Thanks~!

 

Best Regards,

Enwei Hu

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davidtosenovjan
NXP TechSupport
NXP TechSupport

1) Yes, it is over the whole temperature range, but I see an issue in this specification - it does not say specified TUE value are both specified “with calibration”. I will report it as a doc bug.

2) If you see mentioned AN2438, Figure 4., you will see TUE definition, it is basically absolute value i.e. |TUE| = 4. No probability curve is defined.

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3) Error caused by external reference voltage is not included as it is not MCU specification.

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152 Views
enwei
NXP Employee
NXP Employee

Hi David,

OK, thanks very much for your reply~!:smileyhappy:

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