BQ76940: Inaccurate cell voltage reading

Adarsh Verma

Part Number: BQ76940

Tool/software:

Dear Expert,

We are utilizing the BQ76940 AFE to measure cell voltage data, accompanied by a companion IC that relays the data to our microcontroller. According to the datasheet, all AFE's GAIN and OFFSET values are stored in EEPROM and are factory calibrated by TI.

The datasheet also specifies that to calculate cell voltage data, the ADC Transfer Function should be used: V(cell) = GAIN x ADC(cell) + OFFSET.

My question is: Are the values we read already processed through this transfer function, or do we need to enable and apply the transfer function ourselves?

Regards,

Adarsh Verma

2 months ago

0 Maxwell Verboncoeur 2 months ago

TI__Mastermind 19250 points

Hi Adarsh,

The measurements are reported in ADC counts and must be converted to mV by the MCU using the given formula and stored calibration values.

Regards,

Max Verboncoeur

0 Adarsh Verma 2 months ago in reply to Maxwell Verboncoeur

Prodigy 40 points

Hi Maxwell,

As mentioned, we are using the AFE along with a companion IC. The values are transmitted to the microcontroller via the companion IC(BQ78350DBT-R1A). Does the AFE handle all the necessary calibration, or do we need to apply it ourselves?

Regards,

Adarsh Verma

0 Maxwell Verboncoeur 2 months ago in reply to Adarsh Verma

TI__Mastermind 19250 points

Hi Adarsh,

Sorry I missed that part.

The companion gauge converts the cell voltages to mV:

Regards,

Max Verboncoeur

0 Adarsh Verma 1 month ago in reply to Maxwell Verboncoeur

Prodigy 40 points

Hi,

Does it mean, the Companion will take care of the transfer function( V(cell) = GAIN x ADC(cell) + OFFSET) and applies the gain and offset before communicating to MCU??

We have multiple customer complaints and need your quick response to identify the root cause and fix the issue.

Best Regards,

Adarsh Verma

0 Maxwell Verboncoeur 1 month ago in reply to Adarsh Verma

TI__Mastermind 19250 points

Hi Adarsh,

I believe so but I'm not the expert for the companion gauge. I recommend opening a thread with the gauge as the part number so that the gauges team can confirm.

What specifically is the behavior that the customers are seeing?

Regards,

Max Verboncoeur

Power management

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BQ76940: Inaccurate cell voltage reading