BQ76940: 16-bit CC-ADC INL MAX 40lsb fit over range input voltage +-200mv

Y CY

Part Number: BQ76940

On page 11 of the BQ769X0 datasheet, for the 16-bit Coulomb Counter (CC) used in pack measurement with a range of ±200mV, the maximum Integral Nonlinearity (INL) is specified as ±40LSB. Does this imply that its (ENOB) is also 16 bits ?，would there any measurement error?

thanks help

over 1 year ago

0 Max Verboncoeur over 1 year ago

TI__Mastermind 24530 points

Hi,

Yes, I would assume that the ENOB is 16 bits as the test condition explicitly states 16-bit.

Regards,

Max Verboncoeur

0 Y CY over 1 year ago in reply to Max Verboncoeur

Prodigy 10 points

Hi Max,

Thank you for your response. It seems that it has a 16-bit effective number of bits (ENOB). However, I have a question regarding the ±200mV range. If I use a stable current, would a 40LSB error occur? In a BMS application, is a 40LSB error range acceptable in acutal staution?

I look forward to your reply. Thanks.

0 Max Verboncoeur over 1 year ago in reply to Y CY

TI__Mastermind 24530 points

Hi,

The LSB value in the datasheet is 8.44uV. This would equate to a worst case INL current error of 337.6uV / Rsns. With a 1mOhm sense resistor, that is ~337.6mA. Although that's the worst case error. The typical INL error is 3 LSBs which is much better at 25.32uV / Rsns. Due to how INL error works it's hard to say exactly what INL error you will have at what current, but it should be fine.

We have an FAQ for a similar device that goes over the worst-case current calculations and the methods and ideas should be the same for this device: [FAQ] BQ76952: How can I calculate the coulomb counter current error in the BQ769x2? - Power management forum - Power management - TI E2E support forums.

Regards,

Max Verboncoeur