Sixteenth-Brick Converters Are Taking Shape

May 1, 2004 12:00 PM
By David Morrison, Editor, Power Electronics Technology

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As part of the continuing effort to shrink isolated, board-mounted, dc-dc converters, several power supply manufacturers have been preparing to launch the newest package style — the 16th brick — later this year. For the most part, these companies have been developing their products independently, leveraging their own designs to downsize from the eighth-brick form to the smaller 16th brick. However, recognizing their customers' need for multisourcing, these companies have been collaborating to develop products with compatible footprints and pinouts.

This collaboration isn't the work of one large group of power supply companies, but rather several smaller groups who are taking somewhat different approaches to achieve inter-vendor compatibility. Despite these differences, the resulting plans for the 16th bricks are similar. In general, companies plan to shrink the eighth brick by cutting 1 in. off of its length. The resulting 1.3-in. × 0.9-in. footprint will enable the 16th bricks to share the same pin locations and assignments as the industry-standard eighth and quarter bricks, easing the transition from eighth brick to 16th brick.

Although many brick vendors agree on this basic approach, they are less uniform in their focus on package style. Some vendors are pursuing through-hole designs first with surface-mount (SMT) versions to follow, while others are concentrating on developing SMT models.

Last year, Astec Power introduced the ALX Series of 16th bricks, which maintains the same pin locations and assignments of the eighth brick, but its 1.65-in. × 0.8-in footprint differs slightly from what the other vendors are planning (see the table).

Sixteenth-Brick DC-DC Converters*

Vendor/Model	Footprint (in.)	Package Height (in.)	Output Voltages (V)	Max Output Current (A)	Product Introduction
Astec Power ALX Series	1.65 by 0.8 (through-hole with eighth-brick pinout)	0.33	1.2, 1.8, 2.5, and 3.3	20 A at 1.8 V; 18 A at 2.5 V; 15 A at 3.3 V	Spring 2003
Celestica S-Class	1.11 by 0.90 (through-hole with unique pinout)	0.4 (0.5 with heatsink)	1, 1.2, 1.5, 1.8, 2.5 and 3.3	15 to 25 A	Q3
Cherokee SB Series	1.3 by 0.9 (SMT with Celestica pinout)	0.35	1.2 , 1.5, 1.8, 2.5, 3.3, and 5	25 A at 1.8; 20 A at 2.5 V; 15 A at 3.3 V; 10 A at 5 V	Q3
SynQor SML Family	1.3 by 0.9 (through-hole with eighth-brick pinout)	0.335	1, 1.2, 1.5, 1.8, 2.5 and 3.3 (5 and 12 possible)	25 A at 1V to 1.8 V; 20 A at 2.5 V; 15 A at 3.3 V	Late Q4
Tyco Electronics KW Series		0.335	1 to 5	up to 25 A	Q3
Datel ULS Series		0.335	0.8, 1, 1.2, 1.8, 2.5, 3.3 and 5	10 to 20 A	Q4
Cherokee SB Series	1.3 by 0.9 (SMT with eighth-brick pinout)	0.35	1.2 , 1.5, 1.8, 2.5, 3.3 and 5	25 A at 1.8 V; 20 A at 2.5 V; 15 A at 3.3 V; 10 A at 5 V	Q3
Power-One SSQ Family	1.3 by 0.9 (SMT with eighth-brick pinout)	Not available	1, 1.2, 1.5, 1.8, 2.5 and 3.3 (5 and 12 possible)	25 A at 1 V to 1.8 V; 20 A at 2.5 V; 15 A at 3.3 V	Late Q4
*Specifications shown here are preliminary.

However, Celestica Power Systems opted for a unique pinout and footprint with its S-Class family of 16th-brick converters. At 1.11 in. × 0.90 in., the S-Class converter occupies less than 1 in.² of board space, allowing for a power density as high as 141 W/in³. The tradeoff here is the unusual placement and assignment of pins in this through-hole design. The company also plans to develop an SMT version.

In February, Cherokee International said it would support Celestica's design by introducing a compatible model, the SB Series. Although the Cherokee 16th brick shares the Celestica pin assignments and locations, it does not share the same dimensions (Fig. 1). Instead, Cherokee opted for the 1.3-in. × 0.9-in. footprint, which allows an EMI input filter to be integrated into the module. Cherokee's initial SMT package will be followed by a through-hole version.

The same 1.3-in. × 0.9-in. footprint was selected by SynQor, Tyco Electronics and Datel when they jointly announced plans to introduce a 16th-brick converter in April. The announcement indicated that the Distributed-power Open Standards Alliance (DOSA), which counts Tyco and SynQor as its founding members, would be adopting the 1.3-in. × 0.9-in. footprint, along with the same pin-to-pin spacings as the eight brick (Fig. 2) as the DOSA standard for the 16th brick. These companies initially will introduce through-hole versions, but plan to follow up with SMT models.

Meanwhile, a collaboration by Power-One, Artesyn and two other vendors is laying the groundwork for these and other companies to produce compatible SMT versions of the 16th bricks. According to Power One, this effort will establish guidelines for placement of pads on the customers board. The goal is to allow vendors to keep their existing proprietary surface-mount con-nectors, while ensuring vendor-to-vendor compatibility.

As with plans for through-hole 16th bricks, the SMT models will feature pin assignments/locations similar to the eighth bricks. However, in the case of the SMT models, the I/O pads will move closer to the edge of the board, allowing for visual inspection. Tentative plans call for center-to-center (row-to-row) spacings of 1.186 in. for SMT I/O versus 1.1-in. spacings for the through-hole 16th bricks. These companies also have plans to develop through-hole versions of their 16th bricks.

The 16th bricks now being developed are expected to deliver roughly 50 W of output or up to 25 A. For a listing of preliminary specifications (see the table).

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