New board layouts and their associated headaches aren't a desired result; they're what sets of single- and dual-output supplies and distributed power architectures are supposed to simplify.

The triple low-voltage dc/dc modules look to be tied in with the general trend toward integration, such as dual-PWM controller ICs, to power the logic, DSP circuitry and processor cores used in today's machines (see March 25, page 55). But while the board design challenges differ widely between the desktop and the portable/wireless device, system designers still often consider the triple supply to be optimum. Indeed, that seems to be the breakpoint between manageability and unmanageability when addressing power and thermal issues, efficiently placing external components and so on.

Most of the folks building and using controllers are generally sure that two PWMs are about all they want to see on a chip, especially when addressing the end products' time-to-market. But in many quarters, the fascination persists with three, even though it flies in the face of another seemingly sacred design rule: layout symmetry.

I am reminded of Brother Maynard's reading from the Book of Armaments in Monty Python and The Holy Grail: "Then shalt thou count to three. No more, no less. Three shall be the number of the counting . . . Four shalt thou not count, and neither count thou two, excepting that thou then goest on to three. "

Three has actually been "the number of the counting" for a long time in many general-purpose 5-, 12- and 15-V supplies: Any fourth voltage has usually been a low-current, auxiliary output.

But this time, we're dealing with low voltage and sometimes less power, and going beyond the so-called limit won't be a surprise to me.

Indeed, dual-output eighth-bricks are a likelihood. That implies that a four-output supply in a quarter-brick format will be here soon.