BQ27426: largest acceptable current sense resistor

Nicholas Carley

Part Number: BQ27426

Hello,

Our current levels are 0-20mA out of the battery. We'd like to size up the sense resistor to reduce the gain and improve SNR.

How large of a current sense resistor can we use? What would you recommend for 0-20mA range of values? Would we need to reprogram or recalibrate the BQ27426 to account for the larger resistor?

Nick

over 4 years ago

+1 Wyatt Keller over 4 years ago

TI__Guru** 105590 points

Hello Nick,

You should be able to use a larger sense resistor than the 10mOhm, as long as you are within the ADC voltage range. The gauge will only report the current in 1mA steps so you won't be able to get much better resolution reported and you will most likely rely on the chemistry ID for a majority of the application.

Sincerely,

Wyatt Keller

0 Nicholas Carley over 4 years ago in reply to Wyatt Keller

TI__Genius 9885 points

Hi Wyatt,

Is there a register we need to update to let it know the size of the resistor? If not, how does the gauge compensate for that?

I see the maximum differential across the SRP/SRN pins is 2V (section 6.1) but I don't see an operating differential range. Is 2V the useable differential range of the coulomb counter?

Nick

0 Nicholas Carley over 4 years ago in reply to Nicholas Carley

TI__Genius 9885 points

Hi Wyatt,

I wanted to check in on this, any update?

+1 Abraham Rashid over 4 years ago in reply to Nicholas Carley

TI__Expert 3030 points

Hi Nick,

Registers should be updated after you calibrate current.

Recommended range is in table 6.10 in datasheet, ±25mV from BAT pin.

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BQ27426: largest acceptable current sense resistor