4.2.4 Ibat

Acquire a second high-current capable power supply with an adjustable current limit and floating output (with respect to earth ground). Set the output voltage to a minimum (<2V typically) and the output current to a minimum. Enable power and short the output leads (not connected to the PCBA). Set the short-circuit current to the lowest Ibat value shown on the calibrate tab (Figure 4-1). Disable the power supply output.

Now unshort the connections and apply them to the following terminals:

These connections will place the applied current directly across R4, which is the Vbat output current sense resistor.

Enable the high-current power supply output and adjust the output (short-circuit) current to each of the three values shown, clicking the corresponding button to capture the ADC counts for each value.

Once all the necessary calibration steps have been updated, click Write Calibration. The GUI will calculate the slope/intercept values and confirm the values are reasonably linear and within certain ranges. It will then transfer these values to the permanent memory in the embedded CPU (Flash or EEPROM). If the process completes properly, the “Calibration Succeeded.” message will appear.

If there is an error, such as 'Calibration Data is Invalid #10', then there is a linearity issue with the ADC counts captured. Please recheck and resample the values. The GUI is checking for +/- 10% linearity between the estimated slope of the three points. If these values deviate by this much, something may be wrong with the setup.