Power Electronics

Eighth Brick Gains Momentum, Sixteenth Gets Proposal

As bricks and single-in-line packages (SIPs) continue to evolve to deliver more juice from smaller space at lower cost with higher efficiency and reliability, suppliers of dc-dc converters are planning the next move. The drive toward sixteenth brick form factor has begun. Based on statistical data, presented by Mahmoud Sayani of SiMurg Technologies, formerly with Celestica, at last month's Applied Power Electronics Conference (APEC), the sixteenth brick converters should be introduced by the 2005-2007 time frame. Each new form factor has continued to halve the package size since the first introduction of a full-brick in 1984-85, while achieving 65-75% improvement in power performance with each new brick form factor.

While some are investigating the next migration toward the sixteenth brick, Mansfield, Mass.-based Datel Inc. has already taken the first step in that direction. The company has proposed a footprint and pin spacing to make this standard feasible and workable. In addition, Datel designers are exploring planar magnetics, miniature components and novel topologies to pack a high-performance dc-dc converter into the newest brick format that is half the previous eighth brick size. The length has been shrunk to halve, while the width remains the same as in the eighth brick format (Fig. 1).

Unique topologies and clever circuit techniques will be combined with planar magnetics to achieve the end goals, stated Datel's marketing manager Bob Leonard.

Essentially, for the sixteenth brick pin-out, Datel will cut the length in half. Consequently, the rows of pins will now be 1 in. from each other — versus 2 in. for the quarter and the eighth bricks. So, as per Datel's proposal, the sixteenth brick form factor will now have a 1.3-in. overall length (0.15 in. from pin rows to edge of the p. c. board). The sixteenth brick width will be 0.9-in., accommodating the existing 0.6-in. distance available in the existing quarter and eighth brick pins width-wise, as well as the 0.15 in. to the edge of p. c. board. In short, the sixteenth brick format offers a 1.3-in. length and 0.9-in. width, for through-hole and surface-mount versions. Datel intends to deliver 33-50 W power in this format, with output voltages in the 0.9V to 5.0V range. In fact, the maker is considering solutions for 12V and 48V applications. The quad input range for the 12V line will be 9V to 36V, while the 48V versions will offer 36V to 75V input range.

Meanwhile, improvements in the eighth brick format have also gained momentum, as more suppliers jump into this fray to break the $1/A barrier. And give users the security of multiple sourcing. Since launching the first isolated eighth brick solution last year, Datel took the initiative to develop the first non-isolated dc-dc product in an eighth brick form factor. On the heels of this announcement came Artesyn Technologies' newest isolated converter that pushes output current in the eighth brick format to 40A at 1.8V output voltage. In addition, Sweden's Ericsson Power Modules continues to expand its eighth brick dc-dc PKB series, launched last fall, with higher output current at 1.5V and 1.2V outputs. By the month end, the maker intends to unveil an eighth brick member with 30A output current at 1.2V output voltage, in addition to a 28A unit at 1.5V. Another eighth brick player flaunting developments in this arena is Ascom Energy Systems. Like others, Ascom has launched Xena 50 dc-dc converter in an eighth brick footprint with quarter brick pin-out. Xena 50 is designed to deliver 30A at 1.5V output voltage. Another player to join the race is Beta Dyne.

Designed as building blocks for emerging, on-board power-distribution schemes in which isolated 12V buses deliver power to any number of non-isolated, step-down buck regulators, Datels' LEN D12 Series offers 25A of output current with fast transient response for point-of-load (POL) applications. Nine models in this line accept 12V input with a range of 10.8V to 13.2V, and convert it to output in the 0.8V to 5V range. To obtain efficiency as high as 95% for 5V output models, low noise (25 mVp-p typical), tight line/load regulation (±0.25%max.), quick step response (150 µsec), stable no-load operation, and no output reverse conduction, the unit implements a fully synchronous, fixed-frequency, two-phase buck topology. To manage external decoupling capacitors and minimize parasitics, the nonisolated LEN series offers extra interdigitated pins-two for the +output and two commons. The extra output and common pins mean that the VOUT trim pin moves to the input side of the unit. Multilayer ground and power planes maximize transient response. In addition to the remote on/off, a share pin is provided to enable current sharing or N+1 redundancy.

Although the LEN D12 is rated to deliver 25A at ambient temperature of 65°C with 200 lfm air flow without heat sink, it gets derated at higher temperatures. The output current capability drops to 21.5A at 80°C with 200 lfm air flow, which further goes down to less than 20A at 85°C (Fig.2). Datel has readied surface mount and through-hole models.

Isolated Bricks

Hoping to establish new performance benchmarks in the eighth brick offerings, Artesyn has launched a single output isolated unit that flaunts 40A at 1.8V. Its efficiency is 89% at full-load. Of course, this performance is at room temperature. That means, the current capability must drop as board temperature rises to 85°C and above (Fig. 3). According to this figure, the output current falls to 30A at 85°C ambient temperature. Offering an input range of 36Vdc to 75 Vdc, this open frame unit is nonparallelable. And, it offers a transient response of 20 microseconds for a 50% to 75% load step change. High efficiency at high output current and below 2.5V output voltage is attributed to patent pending, full-wave coupled inductor topology, along with improved synchronous rectification and control techniques. The new topology offers the properties of a forward converter, but with output inductor embedded in the output transformer (Fig. 4, on page 60). As a result, there is no high current circulating via the output inductor, thereby saving I2R loss and improving conversion efficiency, noted product manger Jim Nelson.

Optimal synchronous rectification and planar magnetics have enabled the developer to keep the height of the unit to just 7.7 mm (0.3 in.). Additionally, the use of two microcontrollers for house keeping chores and supervisory functions has reduced parts count significantly. The converter has been designed for operation without a heat sink. The unit offers basic isolation of 1500 Vrms. And dc isolation is 2250 Vdc. According to Artesyn, future members will include 1.2V, 2.5V and 3.3V models.

Ericsson continues to boost the performance of its eighth brick members, while maintaining high efficiency and low profile (7.62 mm). The company has raised the predicted MTBF for this product line to 3.7 million hours.

Designed as a drop-in replacements for larger quarter bricks, as well as for new eighth bricks in board mounted power (BMP) applications, Ascom Energy Systems' Xena 50 dc-dc series is targeting the telecom, industrial automation, and computer/server markets. To accomplish high output current at high efficiency from a miniature form factor, Xena 50 combines planar magnetics with several important patents. The result is 30A at 1.5V output with better than 90% efficiency at full-load. And approvals from agencies like UL, CSA, and CE. The Xena 50 open-frame brick family offers an input range of 36V to 75V with single outputs varying from 1V to 5V. The unit offers an extremely low profile of 8.5 mm or 0.335 in.

Other salient features include remote on/off, current limiting, sense lines, trim function, and overvoltage protection. The input to output isolation is 1500 Vdc. And the operating temperature range can vary between -40°C and 100°C. Available in through-hole and surface-mount versions, the calculated mean time to failure at full output power for Xena 50 is 1.9 million hours.

Patented driver techniques for synchronous rectification at the output coupled with surface mount devices and planar magnetics makes it possible for Beta Dyne to launch a new isolated 40W eighth brick single output dc-dc converter with transient response that is comparable to nonisolated solutions.

The new member of the maker's PowerWatt family flaunts 25µS transient response, approaching that of nonisolated, step-down converters. The power density is 60W/cu. in. Other features include up to 91% efficiency, 150µA off-state current, thermal and undervoltage protection, output synchronous rectification, 2:1 input voltage range, input-to-output isolation, soft start, external synchronization, and short circuit protection. Output power falls with rising temperature and requires 400 lfm airflow to maintain 40W output at 75°C, which drops further as temperature rises.

Beta Dyne's eighth brick offers two input ranges. For 24V nominal input, output current is 16.7A at 1.8V output with 84% efficiency at full-load. For 48V input, output current is 16.7A at 1.8V output with 86% efficiency at full-load. Other outputs available include 2.5V, 3.3V, and 5V.

Beta Dyne Inc., Bridgewater, Mass.,
CIRCLE 344 on Reader Service Card

Datel Inc., Mansfield, Mass., www.datel.com
CIRCLE 345 on Reader Service Card

Artesyn Technologies, Framingham, Mass.,
CIRCLE 346 on Reader Service Card

Ericsson Power Modules, kungens Kurva, Sweden,
CIRCLE 347 on Reader Service Card

Ascom Energy Systems, Tucson, Ariz.,
CIRCLE 348 on Reader Service Card

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