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EDN.COMMENT: An unexpected outbreak of common sense

The OMTP (Open Mobile Terminal Platform) is a mobilephonepan-industry body set up by eight mobile operators—including names such as Vodafone, Orange, TMobile,AT&T and Hutchison—but with membership from othersectors, such as equipment manufacturers. The big namesfrom the handset makers are represented there, too. Its statedaims are to “simplify the customer experience of mobile data services and improve mobile-device security.”In September 2007, the OMTP announcedan outline agreement to movetowards a common charging and interconnectionstandard for cell phonesand other portable devices.

Well, break out the champagne.

The organisation has noticed that “there are literally hundreds of millions of chargers and data cables in circulation. On top of that, there is a huge number of different peripherals such as headsets for voice calls, car kits, and data cables—many with different physical connectors.” Any of us could have told them that a long time ago—most of us have at least one drawer or cupboard full of the things, and the paraphernalia that you need to pack to keep your portable products operational while travelling is—or should be—an embarrassment to our whole industry.

So, the industry thinks it might be a good idea to bring some standardisation into this mess. As the OMTP’s statement puts it, “This fragmentation creates unnecessary cost for the whole value chain, creates clutter and limits the freedom of selection for end users, and restricts competition by creating barriers of market entry.”

The rather unsurprising suggestion is that this standardisation be based on the micro-USB connector, allowing mobile products to pick up power from any handy USB port—or, if you have nothing else, allowing you to carry a single charger that outputs USBcompliant power. The situation with data exchange is already, de facto, rather better than for charging power. USB is already ubiquitous, and Bluetooth (where you have it) works well. It’s the multiplicity of charging connectors that’s the problem. The need to carry multiple chargers is especially ridiculous when you consider that almost all of those numerous portable products now use essentially the same power source: some variant of a single lithiumion rechargeable cell.

If anyone was minded to test the concept of using USB, I can save them the trouble. It works. For some time I have not carried a charger for my mobile phone when travelling. I have a USB connecting lead for it, so it picks up its charging current daisy-chained from my laptop. I should confess that this was not an inspirational insight but I was forced to do so when the cheap-andrather- nasty “wall-wart” charger that came with the phone failed, and I couldn’t be bothered to source a new one. One fewer is some sort of progress.

At any time the manufacturers chose to, they could have created sophisticated solution to the problem. You could envisage a completely universal charging strategy, given a bit more resource. Think of two devices with a dedicated connector. On connection, each sets itself into a high-impedance state and looks for logic signals. “I am a power user,” says the product with the battery, “I am a power provider,” says the charger.

“I would like 5V.” “I can give you 5V at 500 mA.” Whereupon both devices agree what they are going to do, switch to a low-impedance state, and charging commences. But that would need a reasonably capable microcontroller, a programmable dc/dc converter, an agreed protocol… it would not be a very expensive parts list, or a particularly complex protocol, but it would have a cost. And the problem with that is, of course, that there is now an expectation—at least on the manufacturing side—that the charger will cost nothing, or as close to nothing as you can get (Reference 1). A universal charging strategy would need the kind of effort and budget that the industry reserves for features that will make money, not for nice-to-have ideas that will not.

But with the ubiquity of USB, you don’t need anything as complex as that. When you can get the same welldefined power line—with full protection included—almost everywhere, why persist with proprietary solutions? On the client side, you can get a dc/dc converter with all the capabilities you need in a tiny area of standard mixed-signal CMOS—as the new product from Wolfson Microelectronics (see pg 12 of this issue) helpfully illustrates.

You might argue that the dataconnection side of the proposal is less amenable to standardisation—but in reality, with the device-discovery features inherent in USB, if you plug a phone into something incompatible or that does not have the right driver, it’s simply going to refuse to talk, and no harm will be done.

If there is a down-side to this proposal, it’s hard to see one. The need has been glaringly obvious, and the start of the process of doing something about it is a welcome move. As soon as you like, please!

REFERENCES

Marsh, David, “Linear regulators face extinction,” EDN Europe, October 2005, pg 29, www.edn-europe.com/ article.asp?articleid=1365.