Energy-measurement Chip Meters Power Distribution Units for Server Farms

"Smart power" usually brings to mind the smart power meters that will eventually sit at every business and home utility box and empower the smart grid. Another layer of applications for energy measurement exists, however: submetering, which measures power usage at the device or power-distribution level. A general utility meter measures power at the utility box when it comes into the facility-for example, a data farm. It next goes into a UPS (uninterruptible-power supply) and then on to the PDUs (power-distribution units), which act as smart power strips, sending the power to eight or as many as 64 channels, arriving ultimately at the power supplies in the servers themselves. At these huge megawatt installations, a variation of 1 percent in power efficiency is enough to win or lose business. However, without submetering at the PDU or power-supply level, the facility can't track power consumption to better than 5 percent accuracy.

To address these issues, the 78M6618 power-metering and -monitoring SOC (system on chip) from Teridian targets data-center PDUs as well as home and business smart power strips by enabling power metering, monitoring, and intelligent relay control of eight single-phase outlets simultaneously. You can control 32 or more channels by connecting multiple chips.

The 6618 has an accuracy of greater than ±0.5 percent over a 2000-to-1 dynamic range and includes self-calibration. It has a 22-bit delta-sigma ADC, 10 analog inputs, a precision voltage reference and digital temperature compensation. It includes a 32-bit computation engine, a microprocessor core, and flash memory. It sells for $5.90 (1000).

How does this pricing play in a world in which you can buy a Kill-a-Watt meter for $25? Jay Cormier, vice president of the energy-measurement division at Teridian, which Maxim-IC recently acquired, puts pricing in perspective: "If you're looking for real-time, accurate measurement, the only way to do it today is to get an AFE [analog front end], which costs about $1. For eight channels, you need eight AFEs, plus a microcontroller that adds another 50 cents. Plus, the AFEs require calibration. The 6618 comes with firmware, which takes out the development time. The chip is about half the cost of the component equivalent."

Teridian
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The self-calibrating 78M6618 power-measuring SoC has an accuracy of >60.5 percent over a 2000-to-1 dynamic range.