topic Re: MC33774ASP1AE : Open-Load Detection for Cell-Terminal Connectivity in S32K

MC33774ASP1AE : Open-Load Detection for Cell-Terminal Connectivity

varunbharti — Wed, 11 Dec 2024 10:16:18 GMT

Hello,

In the MC33774A datasheet (Rev. 2.0, DS743220), section 7.7.1 regarding Cell-terminal pulldown resistors for diagnostic open-load detection of CTx pins mentions the following:

A pulldown resistor can be activated between two adjacent cell terminal pins.
PRMM_APP_CTRL.VCOLNUM selects which switch is closed, and only one switch can be closed at a time.

Based on this, does it imply that Open-Load Detection for cell-terminal connectivity can only be performed for one cell at a time?

I would greatly appreciate clarification on this functionality.

Re: MC33774ASP1AE : Open-Load Detection for Cell-Terminal Connectivity

RafaR — Wed, 11 Dec 2024 19:28:21 GMT

Hi varunbharti

Yes, that is recommended to prevent false measurements by adjacent cells

If you need more information, in the below link you can find in secure files an application note that talks about the open load of this device

https://www.nxp.com/products/power-management/battery-management/battery-cell-controllers/18-channel-li-ion-battery-cell-controller-ic-asil-d:MC33774

Have a great day and best of luck.

Re: MC33774ASP1AE : Open-Load Detection for Cell-Terminal Connectivity

varunbharti — Thu, 12 Dec 2024 05:30:04 GMT

Thankyou

Re: MC33774ASP1AE : Open-Load Detection for Cell-Terminal Connectivity

varunbharti — Tue, 07 Jan 2025 16:37:37 GMT

Hi,

Thank you for being so supportive. Following your recommendation, I referred to the document you suggested and tested the open-wire diagnostics.

However, I encountered an issue during testing. I opened the wires for 4 cells: C0, C2, C12, and C17.

For C0 and C17, I am getting open-load voltages within the expected range.
For C2 and C12, I am observing higher-than-expected values.
Interestingly, for C2 and C12, the consecutive cells (C3 and C13) are showing the expected values.

Additionally, if I introduce a 100 ms delay between consecutive enabling commands:

All cells show results within the expected range.
Consecutive cells also show expected values, even if their wires are intact.

Could you please assist in understanding and resolving this issue?