BQ2980: BQ2980 CHG, DSG abnormal

Hi Star,

This looks like the charge pump is being overloaded. The maximum load is 10uA. Could you check that this is not being exceeded between the CHG and DSG FETs?

Also, just to double check the supply, could you capture the same waveform with the VDD and BAT voltages included?

Regards,

Max Verboncoeur

Hi Maxwell,
Thank you TI two engineers to help!
I checked the datasheet, the detection delay is 250us, it seems to trigger the Short circuit discharge, but I don't have a load connected to it, can you tell me specifically how to test the CHG and DSG FETs. Here are my VDD and BAT waveforms.

VDD and BAT waveforms are consistent

Thank you for your help.

Best Regards,

Kong

Hi Kong,

Could you capture a single waveform during this behavior showing the BAT voltage, the CHG + DSG voltages, and the voltage across the sense resistor?

Regards,

Max Verboncoeur

Hi Max,

Here are the BAT voltage waveforms, the CHG + DSG voltages waveforms, and the voltage across the sense resistor waveforms.

the BAT voltage waveforms

 the CHG + DSG voltages waveforms

the voltage across the sense resistor waveforms.

Best Regards,

Kong

Hi Kong,

Looking at the waveform of CHG and DSG it looks like the charge pump is being overloaded when both outputs are being driven.

Are you able to try forcing either an OV or UV condition with a power supply to cause the device to stop attempting to drive one of the FETs and see if the other output becomes stable?

You may also try removing R62 and R66 and placing ammeters in their place to see what the current load on the charge pump is.

Regards,

Max Verboncoeur

Hi Max，

After I triggered OV and UV protection, it only closed the corresponding FET, but the other FET is still the waveform sent to you above, CHG pin and DSG pin, the ammeter shows 1uA.

Is the cause of this anomaly related to the selection of my resistance value? I hope you can help me confirm it.

Thank you very much！

Best Regards,

Kong

Hi Max，

This is my schematic diagram of bms, could you please check it for me.

Best Regards,

Kong

Hi Kong,

It looks like your schematic has two parallel sets of stacked AFEs. I'm curious as to why your application is designed this way.

Is this behavior occurring in all of the AFEs or just one? Are the other AFEs in a fault state?

Regards,

Max Verboncoeur

Hi Max，

My design is built on the bq2980EVM as I understand it. Can you please provide a reference design about how the bq2980s are combined into a battery pack.

U6 is charging abnormally, discharging normally.

U7 is charging abnormally, discharging abnormally.

U10 and U11 are charging normally, discharging abnormally.

Best Regards,

Kong

Hi Kong,

We don't have any reference designs as this device was not made with stacking in mind. This previous E2E thread (link) goes into more detail on the topic.

Kong Franc said:

U6 is charging abnormally, discharging normally

What do you mean when you say that the AFE is charging abnormally and discharging normally? Do you mean that the CHG pin is showing the abnormal waveform and the DSG pin is at a normal/stable voltage?

Regards,

Max Verboncoeur

Hi Max，
Thanks for sharing the link!

The U6 CHG pin as I posted above, a waveform with a delay of 250us.The DSG pin is at a normal/stable voltage.

Best Regards,

Kong

Hi Max,

I removed the resistors R69,R71,R73,R75 in the schematic diagram .Then I connected the battery directly to the BQ40Z50 as shown in the diagram below.

All functions are normal after operation, can you help me to see if it is a design error of my BQ2980 related circuit?

Best Regards,

Kong