30A, PCB-level supply monitor has integrated 300 µΩ sense resistor
Choosing a sense resistor, Linear says, 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 ±30A. When measuring a full-scale current of 30A, 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 6A rail. In addition to low power dissipation, the LTC2947 offers high dynamic range due to its low offset of 6 mA (or 1.8 µV).
Three integrated Δ∑ 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 the need for 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 suitable for monitoring current levels during short-circuit or blackout situations without additional circuitry.
Specified over the commercial and industrial temperature ranges, the LTC2947 occupies a 32-lead 4 x 6mm QFN package, and pricing starts at $5.95 (1000).
Linear Technology; www.linear.com/products/power_monitors
next page; feature listing
Summary of Features: LTC2947
±30A current range with 300 µΩ integrated sense resistor
Monitors current (1.0%), voltage (0.5%), power (1.2%), charge (1.0%), energy (1.2%)
0V to 15V rail-to-rail input range
Three Δ∑ 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 x 6 mm QFN package
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