Rail-to-rail 80-V power monitor measures current and voltage with greater accuracy

November 08, 2012 // By Paul Buckley
Linear Technology Corporation has introduced a wide range I2C system monitor that monitors the current, voltage and power of any 0 V to 80 V rail.

In many cases, prior power monitoring solutions are limited to 3 V to 5 V supplies and monitor voltages less than 36 V, requiring additional circuitry to monitor higher voltages. The LTC2945 has flexible power supply options, deriving power from a 4 V to 80 V monitored supply, a 2.7 V to 80 V secondary supply, or from the onboard shunt regulator. These supply options eliminate the need for a separate buck regulator, shunt regulator or inefficient resistive divider while monitoring any 0 V to 80 V rail. The LTC2945 is a simple, single-IC solution that uses an internal Delta Sigma ADC and multiplier to provide 12-bit current and voltage measurements and 24-bit power readings.

The LTC2945’s wide operating range is ideal for many applications, especially for 48V telecom equipment, advanced mezzanine cards (AMC) and blade servers. The onboard shunt regulator provides support for supplies greater than 80 V and negative supply monitoring. The LTC2945 measures current and voltage either continuously or on-demand, calculates power and stores all of this information along with minimum and maximum values in I2C accessible registers. Measurements are made with only ±0.75% of total unadjusted error (TUE) over the entire 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 400 kHz I2C interface features nine device addresses, a stuck bus reset timer and a split SDA pin that simplifies I2C opto-isolation. The LTC2945-1 version offers an inverted data output I2C pin for use with inverting opto-isolator configurations.

The LTC2945 and LTC2945-1 are offered in commercial and industrial versions, supporting operating temperature ranges from 0 to 70°C and -40 to 85°C, respectively. Both versions are available today in RoHS compliant, 12-pin 3 mm x 3 mm QFN and 12-lead MSOP packages. Pricing starts at $3.57 each in 1,000 piece quantities.

More information at www.linear.com/products/power_monitors