Polyphase Energy Metering ICs from Analog Devices

The semiconductor business is intensely complicated technically but the basic financial model that drives it is amazingly simple. It costs a small fortune to develop IC technology/designs and a larger fortune to ultimately realize them in silicon. Much of the fabrication expense is allocated on a per wafer basis and so the business really comes down to the problem of how many little square things that work (chips) can you fit onto a big round thing (wafer) and how many wafers do you have to push per month to pay for everything.

The sunk cost of developing a fabrication technology and doing a dedicated design has to be recovered as does some fraction of the fab capital and so what everyone is looking for are parts that they can build/sell in huge volumes.

If you think about electric power metrology it doesn’t take long to figure out that the customer watthour meter is about the only thing in this market space that is made in sufficient volume to attract the attention and resources of significant semiconductor houses. If you do a little internet shopping you will indeed find a plethora of semiconductor companies offering integrated metrology engines or, “meter chips” for short.

In our view, the best of these are made by Analog Devices, Inc. (ADI).

ADI has long been known as a very strong technical company with particular expertise in precision A/D converters and digital signal processing. This is reflected in their ADE device offerings that have parallel A/Ds on chip and do the entire metrology job from analog signals in to numbers out with the powerful additional feature that the sampled data used as input to their calculations is also passed to the user on a high speed data bus in real time. The beauty of this approach is that one can take advantage of these amazingly sophisticated and low cost devices to assemble metrology platforms where all of the standard values are already extracted allowing you focus on the “secret sauce” of your product in your downstream processor at the same time with the same data stream. DJA has already done several successful products with this methodology.

There’s way too much here for a short discussion but the summary message is that these devices can be a very effective way to save both money and time in many new instrument developments. One final note is that ADI is also known for the quality and depth of their data sheets. Two of their most important current offerings (the ADE7880 and ADE7978/7933) are included below. These sheets do more than just lay out the product specs – they really are concept of operations documents that teach the reader a great deal that was hard-won by the ADI designers.

7880The ADE7880 is a full 3-phase, general purpose metrology engine with 7 parallel A/Ds, sophisticated DSP and a register-based user interface. It includes a very powerful frequency domain analysis engine on the same device and is one of a very few of these devices that can directly accept a di/dt (Rogowski) current sensor input.
7978The ADE7978/7933 is more of a conventional meter chipset but showcases their iCoupler technology. What this does is provide on-chip isolation for the power and signal paths that allows the use of simple external shunts as current transducers.

ADI offers inexpensive evaluation boards and full-featured software support for those boards for free on their website (http://www.analog.com/en/products/analog-to-digital-converters/integrated-special-purpose-converters/energy-metering-ics/ade7880.html and http://www.analog.com/en/products/analog-to-digital-converters/integrated-special-purpose-converters/energy-metering-ics/ade7978.html)