powerZONE Products for the week of May 31, 2004
Enpirion Says . . .
EN5330: Integrated Inductor In Dc-Dc Converter For
Point-of-Load
10 W of output power; 3 A of output current; Up to 90% efficiency
Switching frequencies of 5x to 10x over competitors
Enpirion, Inc. announced the introduction of the world's smallest Power System on a Chip (PSoC) and the world's fastest synchronous buck converter. The EN5330 is the first of the iPOWER line of integrated DC-to-DC converters for use in Point of Load (POL) applications including servers, personal computers, laser printers, set-top boxes, and telecommunications and data communications equipment. Enpirion, a fabless semiconductor company founded in 2001, has been engaged in extensive R&D on integrated power technologies leading up to the market-release of its first product.
Enpirion's disruptive technology will change the way development engineers approach supplying and managing power in a wide variety of products. The EN5330 -- the first to feature an integrated inductor -- reduces real-estate requirements and part count by more than half, while slashing development costs and time-to-market. Enpirion's patented approach capitalizes on semiconductor geometry advances that enable a 10x switching-frequency improvement, integrating a PWM controller, output FETs and magnetic components into a single turnkey IC package with a standard TSSOP footprint.
"With the increase in the number of voltages required on a single board, the space savings, ease of use and low profile of Enpirion's device offers design engineers a very compelling POL solution," said Vishal Sapru, research analyst with Power Supplies and Batteries practice at Frost & Sullivan.
"Enpirion's power converter, by virtue of its design, effectively addresses the key challenges faced by the power management industry which includes increased integration leading to reduced form factor and efficient thermal management. Its desirable board space savings feature will be a potent influencing factor for its adoption in various applications as occupation of significant space has been an inherent disadvantage for power management ICs", notes Deepa Doraiswamy, Research Analyst with Semiconductor practice at Frost & Sullivan.
The EN5330 is in a Dual Flat No-lead (DFN) TSSOP footprint package that covers just over 100mm² of board space. Including the minimum of three external components, the entire DC-to-DC converter can be placed in as little as 135mm² of single-sided, or 102mm² of double-sided board space. Combined with a height profile of 2.2mm and efficiencies up to 90%, the EN5330 is the perfect POL power solution for applications with even the smallest space requirements.
"Very high switching frequencies enable us to offer a DC-to-DC converter that is truly a complete Power System on a Chip," said Dr. Ashraf Lotfi, CTO of Enpirion. "These frequencies significantly reduce the amount of input and output capacitance required while at the same time offering an order of magnitude improvement on transient response."
Operation from common voltage rails of 2.5V, 3.3V and 5V is achieved with a wide input voltage range from 2.375V to 6.5V. With up to 3A or 10W of output power, the output voltage is VID pin selectable with options for seven standard voltages (0.8V to 3.3V) and a resistor divider setting enabling a continuous set-point range from 0.8V to VIN. The EN5330 can be used in a sequenced start-up with a programmable soft-start time and a separate enable function. Full protection functionality is offered with over-current, short-circuit, over-voltage, under-voltage and thermal shutdown features.
"A number of OEMs have indicated to us that the power section takes
up a third or in some cases up to 75% of their board space," said Mark
Downing, CEO of Enpirion. "With the Enpirion iPOWER POL solution and
the inherent space savings, those OEMs can potentially reduce that fraction
by 50% to 60%, directly contributing to a reduction in the overall system
cost. This significant reduction in board space requirements, coupled with
the reduction in development time and product cost, enables our customers
to have a faster time to market and to be more competitive in their markets."
analogZONE Says...
The challenge in PWM dc-dc buck converters has been to get the switching frequency higher so that the size of the external components can be reduced -- for both cost and real estate. At the same time you get to a point where the inductor required becomes so small that it is nigh impossible to source it commercially and, just for an extra kink, the efficiencies of the circuit start to fall. I rather expected the first "non-inductor" solution to be one where the inductor was so small that a vendor would be able to provide it with bond wire inductance, but Enpirion have blown that expectation for me.
The EN5330 uses a MEMS inductor structure in what is a module solution with a switching frequency of 5 MHz, plus on-chip power MOSFETs, greatly reducing the size of the few external components required -- which are three small ceramic capacitors (input, output and soft-start). At the same time efficiency numbers are way up there.
Enpirion was founded in 2001 as a fabless vendor designing this first part using multisourceable sub-micron CMOS. The principals share AT&T, Lucent and Agere in their backgounds and they recruited analog veteran, Mark Downing, (Micrel, Pericom National and Ferranti) as the CEO. Enpirion has also put Frank Weigold on its Board of Directors, where his previous experience as General Manager of ADI's MEMS business will be invaluable. The company has reached the production point of this product with only one round of funding ($8 M) which will please the investors no end.
The architecture of the part is fairly standard with a type 2 compensation on the VSENSE input; if Type 3 compensation is needed an external series resistor/capacitor can be added. The bandgap reference is on chip as is the sawtooth generator used. Power good logic, overcurrent protection, undervoltage lock-out (2.2 V with a 100 mV hysteresis), and thermal shutdown are all provided.
One of the major "other" achievements from this part is that is provided with a voltage selector process (or will be on final production parts) with the state of three input pins determining the voltage divider on the VSENSE pin and therefore selecting the output voltage. Those eight choices provide a position for an external divider, plus 0.8 V, 1.2 V, 1.25 V, 1.5 V, 1.8 V, 2.5 V, 3.3 V. This means for Enpirion that they have dramatically simplified their inventory position! And for the designer he now has a single layout solution for a multiple of output voltage needs. There will, no doubt, also be designs that will use the feature as a "margining" tool which could be part of an external DSP control loop.
The input voltage range for the part is from 2.375 V to 6.5 V and, obviously, the closer the input rail voltage is to the required output voltage the more efficient the conversion will be. Efficiencies in excess of 80% look very possible across the full range, and with attentive designs the numbers should be 85% and better. Quiescent is typically 15 mA with a 3.3 V rail and an enable pin is provided. The line, load and temperature regulation numbers are all better than ±2%. Response time to processor load changes is better than 10 µs.
The input capacitor is typically going to be 10 to 20 µF with 50 µF on the output. This is a 3-A part although efficiency is maximized around the 1 A point. Two grounds are provided with four pins being used for power ground and a separate pin for analog ground -- which all need to be connected together at a single point off-chip. To provide the current rating four pins are used for the supply and five for the voltage output. Nine pins are left where no electrical connections at all should be made. Thermal pads for power ground and output voltage are provided on the package.
This solution has an awful lot going for it: an external parts count reduction from a typical 11 - 17 to 3; a dramatic reduction in real estate and height; eliminating the hard-to-source, hard-to-handle inductor; simplifying design for multiple voltage solutions; and, not least, a much better control of the EMI situation. The only concerns would be Enpirion's ability to leverage its fab partners when space crunch times come, and the simple fact that the company needs to get its message out very loud and very clear to the designers who will source the parts -- while making the buyers happy that they are going to be around to be a reliable source. Selling the product as a "power system on a chip dc-dc converter" is not the message that design engineers are going to respond to. The arenas for design-in are, of course, copious. The price is a downright bargain when you look at the BOM for a conventional 3-A buck converter.
The EN5330 (with external voltage select) is available in DFN-36 with a Pb-free option, priced at $4.95 in 1000-piece lots. The data sheet indicates that a QFN version will be produced. Evaluation boards are also available.