The BQ25731 uses I²C compatible interface for flexible charging parameter programming and instantaneous device status reporting. I²C is a bi-directional 2-wire serial interface. Only two bus lines are required: a serial data line (SDA) and a serial clock line (SCL). Devices can be considered as host or target when performing data transfers. A host is the device which initiates a data transfer on the bus and generates the clock signals to permit that transfer. At that time, any device addressed is considered a target device.

The device operates as a target device with address D6h, receiving control inputs from the host device like micro controller or a digital signal processor through REG00-REG3F. The I²C interface supports both standard mode (up to 100 kHz), and fast mode (up to 400 kHz). connecting to the positive supply voltage via a current source or pull-up resistor. When the bus is free, both lines are HIGH. The SDA and SCL pins are open drain.