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09-20-2016

30A Supply Monitor with Integrated 300μΩ Sense Resistor Simplifies Board Level Energy Measurements

Linear Technology » LTC2947

Linear Technology Corporation introduces the LTC2947 power and energy monitor for 0 V to 15 V DC supply rails. Most power and energy monitoring ICs use an external sense resistor to measure current. However, choosing a sense resistor is not an easy task, especially when dealing with high currents, where available sense resistors can dissipate too much power, occupy a lot of board space or have a large impact on measurement accuracy. The LTC2947 integrates a 300 μΩ temperature-compensated sense resistor to alleviate these concerns, providing users with a simple 24 mm2 solution that provides up to 1.2% accurate energy readings at up to ±30 A. When measuring a full-scale current of 30 A, the voltage drop over the LTC2947’s integrated sense resistor is only about 9 mV, causing power dissipation of approximately a quarter watt or about 10 mW when measuring a 6 A rail. In addition to low power dissipation, the LTC2947 offers high dynamic range due to its low offset of only 6 mA (or 1.8 μV).

Linear Technology - LTC2947

Three integrated ΔΣ ADCs and an internal or external precision time base (crystal or clock) enable accurate measurement of multiple parameters, including current, voltage, power, charge, energy, temperature and time. All digital readings, including minimum and maximum values, are stored in registers accessible by a selectable I2C or SPI interface. An alert signal notifies the host when measurements exceed configurable warning thresholds, eliminating burdensome polling. The LTC2947 provides access to all the necessary parameters to accurately assess and manage board level energy consumption, and its rail-to-rail operating range is ideal for monitoring current levels during short-circuit or blackout situations without additional circuitry.

The LTC2947 Typical Application
The LTC2947 Typical Application.

Specified over the commercial and industrial temperature ranges, the LTC2947 is offered in a 32-lead 4 mm × 6 mm QFN package. 1,000-piece pricing starts at $5.95 each. Device samples and evaluation circuit boards are available online or from your local Linear Technology sales office.

Energy Measurement Total Unadjusted Error vs Current, VP - VM = 12 V
Energy Measurement Total Unadjusted Error vs Current,
VP – VM = 12 V.

Summary of Features: LTC2947

  • ±30 A Current Range with 300 μΩ Integrated Sense Resistor
  • Monitors Current (1.0%), Voltage (0.5%), Power (1.2%), Charge (1.0%), Energy (1.2%)
  • 0 V to 15 V Rail-to-Rail Input Range
  • Three ΔΣ ADCs for Instantaneous Multiplication of Voltage & Current
  • Internal ±1% or External Time Bases
  • Continuous Scan & Snapshot Modes
  • Maximum & Minimum Value Tracking
  • I2C or SPI Configurable Interface
  • 32-Lead 4 mm × 6 mm QFN Package

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