Hi,
We have a question with bq27x00’s board offset measurement.
In SLUA338 p4 PKCFG[4-2], it requires “no charge or discharge current flowing and subtracting the offset of just the gauge alone”. This is little bit confusing.
First is that the gauge’s VCC pin must be connected to the battery. Then even if the host system is off there is still tiny discharging current due to bq27x00 itself. So does the requirement mean to ignore this discharge current due to the gauge itself?
Second is that who is going to access the gauge? In order to measure the board offset the gauge must be installed on the PCB board of the product but not on the EVM or tester/programmer. To make sure that there is neither discharging nor charging current, the only way it to first make the battery charged, which means no further charging current will be applied; and then keep the DC supply on, so at this time the dynamic power management of the PMIC will solely draw current from the DC supply but not the battery. Only at this time can the both requirements be satisfied and the host can program CEO/CIO commands and reads values.
So is this what we should do?
However when the DC is on and the CPU is working, do they affect the board affect in some way? What is actual the definition for external and internal offset, can there be a more clear explanation?
Noah
