ADC reading issues for current acquisition.(RD33771-48VEVM, SPC5744, MC33771)

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ADC reading issues for current acquisition.(RD33771-48VEVM, SPC5744, MC33771)

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issacs83
Contributor I

Hello,

I am currently implementing BMS using the RD33771-48VEVM product.

However, I'm trying to solve a problem that seems to be stubborn in development.

 

There was a problem reading the ADC value through the shunt resistor and converting it to a current value.

The problem is that the read current value is fluctuating too much, even though the shunt resistor has no load and is open.

 

I'm developing with the programming guide as shown below.

 1.png

 

After initialization, the ADC was started by setting the SOC bit of the ADC_CFG register to 1 as shown in the code below.

Then, we checked whether the EOC_N bit of the ADC_CFG register is 1, and if it is set to 1, we read the ADC register values and processed them according to the programming guide.

($2D[CC_NB_SAMPLES] ~ $4A[MEAS_xxxx])

2.png

 

The values below are the data sent to CAN for the register values.

3.png

 

The value of 18820100 ID above calculated the FFFFFFCE value as below.

0xFFFF FFCE => -50

-50 * 0.6μv/100μΩ = -300mA

Is this correct?

And…

Using an electronic loader, I applied a 100mA load through the + terminal of the battery and the end of the shunt resistor, but the ADC value didn't change, it just bounced around like before.

 

Could it be a broken IC?

Or is it something I'm controlling incorrectly?

I'm curious to know which part is the problem.

 

Any help would be appreciated.

#RD33771-48VEVM
#SPC5744
#MC33771C

#NXP Employee

#NXP TechSupport


@TomasVaverka @jann_ @lisettelozano @guoweisun @mariuslucianand 

ADC reading issues for current acquisition.(RD33771-48VEVM, SPC5744, MC33771) 

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