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# BQ35100: Current Resolution

Part Number: BQ35100

Hi.

Registers 0x0C & 0x0D are the 16-bit signed value for the battery current measured, being the voltage across the (normally) 0.1 ohm sense resistor.
The value has a range of -32,678mA - +32,767mA.

(1) The sense resistor value is normally 0.1 ohms. The maximum voltage across this sense resistor is -/+ 0.125V. Therefore the maximum current measured is -/+ 1.25 A, i.e. -/+ 1250mA.
This is a much smaller range than the -/+ 32,767mA range of the 16-bit signed value. I guess the MSB's are just set to all 1's/all 0's?

(2) If the maximum battery current in use is greater than -/+ 1.25A, a smaller value for the sense resistor is required, e.g. 0.05 ohm for -/+ 2.5A.
If this is done, is there a way to configure the gauge so that it adjusts for this? At present I am using a suitable scale factor in the firmware that drives the gauge.

Simon W.

• Hello Simon,

The sense resistor can be adjusted for the current expected in your application, if you are expecting higher current you will need to decrease the sense resistor size to be within the voltage range of the ADC. The current is adjusted using the CC gain and CC delta values in our firmware. You can follow the EVM users guide for how to calibrate the current, usually we recommend doing this using around 2A if possible.

You can check the calibration section here:

https://www.ti.com/lit/pdf/sluubh7

Sincerely,

Wyatt Keller

• I did wonder about doing it this way. Thanks for confirming.
I think it amounts to the same thing - a suitable scale factor is needed somewhere.