BQ76930: Temperature sampling abnormality

Hi Annie,

Could you explain what you mean by the voltage sampling jumping? Also, what you mean by shielding the temperature measurement?

Are there any faults reported in the registers?

Also, TS1 must have a thermistor or pulldown resistor to VSS even if not in use:

I don't see one on the schematic. Could you check that?

Regards,

Max Verboncoeur

Hi Max,

Customer measured the voltage of 6 batteries in total. If the software turns on the temperature measurement function, the voltage of the battery cell may sometimes fluctuate by 100mV. For example, the current battery voltage is 4.2V, and it will become 4.1V in the next second. If the software turns off the temperature measurement function, this situation will disappear.

TS1 is connected to the IO port of the microprocessor, with the purpose of waking up the BQ76930 through the microprocessor.

Regards,

Annie

Hi Annie,

Even if the measurements are disabled and the pin is just used for waking the device, it is required to have a resistor or thermistor between TS1 and VSS:

The customer may try checking to see if there is an XREADY fault reported by the device during this behavior. 

Regards,

Max Verboncoeur

Hi Max,

The customer has added a 10K resistor between TS1 and VSS, and no XREADY fault is reported, but the problem cannot be improved.

In addition, he also found that the measured voltage of the sixth cell was tens of mV lower than the actual voltage. If only the temperature measurement is affected, he can disable the temperature measurement of the BQ76930 and use the microprocessor to measure the temperature. But the measured voltage of the sixth battery will be lower than the actual voltage, which is difficult to solve. Which pins of BQ76930 are related to voltage measurement? Are there any inappropriate places in the schematic?

Regards,

Annie

Hi Annie,

I don't see anything else off about the schematic.

I recommend that they capture a waveform of the voltage between the VC9 and VC10 pins while this is happening. If any of the other cell voltages are doing this, I recommend measuring those inputs as well to help narrow down if the root cause is internal to the device or if something is occurring before the signal reaches the device.

Regards,

Max Verboncoeur