Calibrating the Current Offset Bias (COB) Register for the DS278x Family of Fuel Gauges

The DS278x family of stand-alone fuel gauges provides an accurate estimation of the remaining capacity available in rechargeable lithium-ion or lithium-polymer batteries. These fuel gauges contain a current offset bias (COB) register that can be utilized by the designer to eliminate the inherent offset introduced by the IC's current Analog-Digital Converter (ADC). Improper calibration of this register, however, can decrease the accuracy of the current measurements, especially at low currents.

This application note describes a step-by-step approach for properly calibrating the DS278x within the fully assembled battery pack in order to determine the correct value that should be placed into the COB register.