MC33771B AFE - Current Issue

[sathish1]

We are working on High Voltage BMS using NXP AFE MC33771B and S32K144 MCU . We are facing issue while measuring the current with AFE chip. We are able to get proper voltage, temperature but the current value is fluctuating . But we did not observe this fluctuating during TPL communication. 

Will there be any difference in using TPL AFE for SPI communication.Please find the below part number used for our testing

AFE Part Number:MC33771BTP1AE

Kindly suggest us the reason for current fluctuation and how to fix this issue.

[TomasVaverka]

Hello Sathish,

First off, are you using any of NXP’s BMS complete reference designs or separate evaluation boards with MC33771B and S32K144 stacked together? Please describe your HW setup as much as possible. Are you using the recommended filter on the current channel as described in the datasheet?

Secondly, are you using NXP’s BCC SW driver or your own code? How are set the ADC2_DEF bits?

Thirdly, please share your test results illustrating the current fluctuation you are observing.

Best regards,

Tomas

[sathish1]

We made our custom board with MC33771BTP1AE and S32K144 MCU.We made use of 100uOhms shunt for current measurement( Part Number- WSLP5931L1000FEA).

We Made use of the recommended current filter section only. And we are using NXP BCC SW Driver only.

Please find the excel sheet for test values with no load and Load condition.