Demonstration Circuit 1674A-B is dual input power manager/3.5A LiFePO4 battery charger with I2C control and USB On-The-Go (OTG) featuring the LTC4156EUFD. Most functions on the LTC4156 are controlled via the I2C serial interface. The LTC4156 also provides extensive status information via the I2C interface. The DC1674A-B's working input voltage range is 4.35V to 5.5V on both the WALL and USB input. The DC1674A-B will tolerate non-operating overvoltage inputs up to 27V. It utilizes the DC590B (USB-to-I2C interface board) to control the LTC4156 and to read back the contents of the command and status registers.