Problems with the isense measurements in the mc33771C

[David_Estevez]

Good morning,

We are using the s32k144 microcontroller connected to the MC33664 adapter as hardware and the MC33771C as BMS together with the monitoring sample program. We are also using a 100uOhm shunt resistor.

When measuring the values ​​in the program with the "domeasuraments" function, it reads the voltage values ​​correctly but the Isense values ​​are always 0. We also activate the Isense measures enable bit in the SYS_CFG1 register. Could you tell us what the problem could be?

Thanks in advance!

[diazmarin09]

Hello David, 

I hope all is great with you. Thank you for using the NXP communities.

Could you please share more details about your design? I mean, are you using an evaluation board? What is the project or libraries used in your project? 

Regards,
David

[David_Estevez]

We are using as hardware a board made up of the s32k144, the MC33664_sds and the MC33771C.We are also using a rshunt of 100uOhms.

About the software we are using the BCC_S32K144_Monitoring program. We change the initialization of the SYS_CFG1[ I_MEAS_EN]=1.  So we initialize the SYS_CFG1 register with the 0x1201 value, I think that is correct.

For getting the voltage of the cells we use the BCC_Meas_GetCellVoltages function and we receive the correct values. But when measuring the current value and we use the BCC_Meas_GetIsenseVoltage function we only receive a 0. 

Measuring with a multimeter we know that between the ISENSE+ and ISENSE- pins there is 0.5mV so the value of the current should not be 0.

I attach you the main.c to see if you see any errors in the main functions.

Thanks in advance!

[diazmarin09 · Accepted solution]

Hello David, 

You are correct, the I_MEAS_EN bit from the SYS_CFG1 register enables or disables current measurement (disabled by default).

The BCC_Meas_GetIsenseVoltage should be useful for you as it reads the ISENSE measurement and converts it to [μV].

Could you please share your ISENSE pins configuration?

[David_Estevez]

Hello again,

The problem was that we were sending the wrong value to SYS_CF1 so we were not enabling the I_MEAS_EN

Thank you!