SAN FRANCISCO Leveraging its ability to integrate a microelectromechanical systems-like inductor on the same IC with a switching regulator controller, Enpirion Inc. is offering a complete dc-to-dc converter on a chip.
Using experience acquired at Bell Labs and AT&T's power supply group, Enpirion hopes to bulldoze its way into the burgeoning market for miniature power management devices with a family of dc-to-dc converters in what could prove to be the smallest form factor yet.
In its initial incarnation, the iPOWER device family introduced this week (May 25) targets workstations and servers with a single-output step-down device that transforms 5 or 3.3 volts to a lower voltage for on-board components. The miniature size, fast transient response and voltage-scaling ability of the converters make them suitable for handheld, battery-powered electronics, Enpirion said. The miPOWER family, targeted at mobile electronics, will be formally introduced in the third quarter, according to marketing director Brett Etter.
The first member of the iPOWER family, the EN5330, incorporates two technological tricks to deliver high current from a tiny TSSOP package (12.5 x 8 mm), Etter said. The first, historically difficult to implement, raises the commutation frequency of the switching regulator. The other crafts the main transformer as a spiral inductor with MEMS technology that sandwiches it between two magnetic cores on the chip surface.
Most conventional switch-mode regulator circuits operate near 250 KHz, while the more ambitious devices (those promoting higher current outputs from smaller form factors) are cycling at around 1 MHz. Thus, at typical 5-MHz operation, Enpirion's switching regulator operates at as much as 10 times higher frequency than conventional switch-mode parts. The fast switching frequency also enables a fast response to voltage-and-frequency scaling requirements, a growing requirement for portable devices.
While elevated switching frequencies can reduce the values and size of the ancillary components capacitors and inductors it can also render the switch-mode circuitry unstable. Efficiency is also sacrificed if all components aren't carefully matched. Enpirion's EN5330 claims 90-percent efficiency with a 1-A output and 85- percent efficiency at 3 A.
"No question, this is an interesting technology," said Gary Grandbois, senior analyst with market researcher iSuppli Corp. (El Segundo, Calif.). "They're in the provability stage right now," he said. "But the payoff for portability is probably great."
Indeed, there are high hopes for Bloomsbury, N.J.-based Enpirion and its technology. It was founded in 2001 by Ashra Lofti and William Troutman, veterans of Bell Labs, Agere Systems, Lucent Technologies and AT&T Power Systems. Lofti serves as president and CTO, while vice president Troutman is the interface to Enpirion's foundries partners.
The management team has attracted considerable investment capital. Series A funding totaling $8 million worth was led by Canaan Partners and SAS Investors.
The EN5330 targets point-of-load (POL) converters in servers, workstations and desktop PCs. The device accepts input from 6.5 to 2.375 volts, and can covert them to the lower-level voltage used by processors and logic devices on a board. A 3-bit code is used to set the output to 3.3, 2.5, 1.8, 1.5, 1.25, 1.2 or 0.8 volts.
Despite the savings in board space and bill-of-materials (up to 70 percent, according to the company), analysts wondered whether the iPOWER is the right part for desktop machines using multi-output, multi-phase devices to generate the multiple voltages required on a board. A higher-voltage device one with a 12-V input may have more utility in server card cages.
While tailoring the pulse-width modulator core to the specific POL voltage and current requirements (up to 9 A) that flow from a 5-V source, Etter said Enpirion's roadmap for next year targets a 1.8-V platform capable of handling up to 6 A, then a 12-V platform capable of delivering up to 12 A.