Accurate monitoring of power is an essential part of a reliable and energy efficient (green) system design. Measuring voltage and current of low voltage (1.8V to 36V) supplies is straightforward, but higher voltages present additional challenges. In this video, we will show the LTC2945 wide range I2C system monitor. This device monitors the current, voltage and power of any 0V to 80V rail, and the rail-to-rail current input allows the sense resistor to be either at the high side or low side of the supply. The LTC2945’s wide operating range is ideal for many applications, including 48V telecom equipment, advanced mezzanine cards (AMC) and blade servers. The LTC2945 measures current and voltage with a 12-bit Delta Sigma ADC, calculates power, and stores this information, along with minimum and maximum values, in I2C accessible registers. Measurements are accurate to ±0.75% over the entire operating temperature range. If any parameter exceeds the user-programmable limits, the LTC2945 flags an alert register and pin per the SMBus alert response protocol. The 400kHz I2C interface features nine device addresses, a stuck bus reset timer, and a split SDA pin that simplifies opto-isolation.