Issue Reading Current from MC33772C in TPL-Based BMS Setup

[Hareesh]

Dear NXP Team,

We are currently working on a BMS solution using the following setup:

• MCU: S32K344

• AFEs: MC33774A (for cell voltage and temperature), MC33772C (for current measurement)

• Transceiver: MC33665

• Protocol: TPL

• Reference Software: HvBms400_774_722_TPL_Bring_Up example code

We are able to successfully read cell voltages and temperature values from the MC33774A. However, we are facing an issue with reading the current values from the MC33772C.

We observed the following:

• A 0.25 mV voltage drop across the ISENSE+ and ISENSE− pins of the MC33772C when applying a 5A load.

• Despite this, the measured current value read via software remains 0 or invalid.

Could you please assist us in resolving this issue? Any guidance or checks you recommend would be appreciated.

Best regards,
Hareesh

BATTERY-MANAGEMENT-CONTROL MC33772C MC33774 MC33665A S32K344-WB  

[RafaR]

Hello Hareesh

The way you describe your problem makes me think that maybe you missed activating the current measurement.

Please refer to the section 9.6 in the MC33772C datasheet. Please make sure, that you have enabled the current measurement chain in the SYS_CFG1 register, bit I_MEAS_EN. By default the current measurement channel is disabled.

I hope this information has helped you, please let me know if you need help with anything else.

Have a great day and best of luck.

[Hareesh]

Hi @RafaR ,

Thank you for the support.

I have verified the SYS_CFG1 register settings during runtime, and I can confirm that the I_MEAS_EN bit (bit 9) is properly set I am writing the value 2560 (0x0A00) to SYS_CFG1 (register address 0x03), which corresponds to enabling the current measurement chain (refer attached image). The bit field breakdown confirms this:

     0x0A00 - 0000 1010 0000 0000

• Bit 9 (I_MEAS_EN) = 1 →  Current measurement enabled

So it appears that the current measurement feature is enabled correctly on the MC33772C side.

Please let me know if there are any additional settings or steps that should be configured to successfully read the current value via TPL communication.

Thanks again for your guidance.

Best regards,
Hareesh

[RafaR]

Hello Hareesh

Good day!

Sorry for the delay in responding. I reached out to a colleague to take a look at the case and get his opinion.

1.- Could you split the photo you shared into two parts, so we can see both the back and front separately?

2.- if you have a tpl sniffer it will be good to have the tpl traces?

I will be waiting for your response

Have a great day and best of luck.

[Hareesh]

Hi,

Could someone please assist me in resolving this issue?

I would appreciate your guidance or any suggestions you might have to help address the problem.

Thank you in advance for your support.

Best regards,

Hareesh

[RafaR]

Hello Hareesh

I am working on it, I will contact you soon.

[Hareesh]

Hi @RafaR ,

I wanted to check if there’s any update?

Your quick response would be greatly appreciated.

Please let me know if you need anything further from my side.

Best regards,
Hareesh