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Power connectors boost system airflow

Posted: 01 Dec 2008 ?? ?Print Version ?Bookmark and Share

Keywords:power connector? airflow system? backplane?

System power connectors from Molex and FCI allow improved airflow.

As servers, storage and networking systems become more powerful they must dissipate more heat. Connector manufacturers are doing their part by developing new power connector designs that allow for more system airflow while handling higher current. This translates into higher performance, lower energy use and savings.

"What's driving the demand for more power in any system is the silicon!there is more of it, and with lower voltages," said Michael Bean, product manager for connector products at Molex Inc. "Any time you combine those two you're going to need a lot more current to be pushed through your power supply. You need a greater wattage power supply and that translates into much higher current being transferred from the power supply into your system."

As a result, the challenge has become between allowable space vs. current demand, which is forcing designers to investigate the effects of the total system, Bean said. This includes the overall connector size and profile vs. rated current, and available thermal assistance!in terms of airflow, copper weight, and trace size.

From a connector standpoint it's the physical contact!material and design!to push more current through either the same or smaller spaces, Bean said. "It's also the analysis of the performance curves associated with the connectors in terms of T-Rise and voltage drop, which is becoming more important because of the lower voltages of the silicon."

Density comparison
The conventional way of looking at power connectors is by citing linear density, how many amps can be pushed through a connector based on linear real estate on the edge of the PCB. However, according to Bean, this doesn't consider height. You must also consider frontal density!comprised not just of the connector but of the space on the power supply the connector takes up. Frontal density is based on 1-inch of linear PCB length multiplied by the connector's face height.

A connector that is 2 inches high could pass much current through it, but the trick is to make a connector only 7.5mm tall off the board and push just as much current through it while providing good linear current/density, Bean said.

In a design using a 1U power supply that is 39mm tall and a connector with a height of 25mm, a good deal of airflow would be blocked. Power supply performance would suffer because of the difficulty in cooling the electronics, according to Bean.

Many of these new connector designs deliver significantly better power densities and open up space to move air more freely inside servers and storage network equipment, allowing fans and other cooling devices to do their jobs more effectively and use less energy.

One example from Molex is the Extreme low profile hybrid (LPH) Power connector. This is a mixed, high-current power and signal connector system. Designed with power blades parallel to the PC-board, its height of only 7.5mm allows greater system airflow while taking up 53 percent less space than conventional connectors with the same current rating. The Extreme LPHPower system gives up to 127A per linear inch.

The LPH provides the same amount of current as conventional SSI power connectors in the same linear amount of real estate at half the height but only takes up 17 percent of that opening on the power supply, which maximizes airflow, Bean said.

Molex is also leading the way for predictive modeling for power connectors. Power integrity is just as important as signal integrity to predict the performance of the connector, Bean said. Predictive modeling for power integrity includes joule heating, finite element analysis and computational fluid dynamics along with all the electrical analysis.

The airflow effect
"One of toughest things is to get designers to pull away from just looking at the current rating in still air even though they know they have airflow over connector," said Bean. "They are using it as safety margin and are not optimizing their connector choice for their application. There will come a point where they will have to start looking at what that airflow means."

As an example, if you add airflow to a LPH power connector of about 70cfm you gain approximately 9A per contact. So if a contact is rated at 26A and you put 70cfm over that connector, you can effectively get 35A out of the connector multiplied by the number of contacts, said Bean.

He added that there is a point of diminishing return with airflow but it shows the importance of a little airflow.

FCI has also developed a power connector design to optimize airflow. The HCI connector system features a vented but touch-proof housing to optimize airflow above, below and through the connector. The touch-proof HCI housing is designed to optimize airflow through the connector by providing vents above the signal field as well as vents above the power contacts that permit airflow away from the mated interfaces and along the entire length of the contacts.

Aimed at applications with increasing system power demands that are driving the need for greater power density, a single HCI power contact accommodates over 82A based on a 30<C temperature rise with zero airflow. This high current-carrying capacity coupled with a molded-in guidance system makes the system well-suited for high-wattage, blind-mate power supplies, according to FCI.

Minimizing heat
Tyco Electronics Corp. has also developed a power connector that addresses heat build-up. Designed to complement the company's most popular high-speed backplane connectors including Z-pack HM-Zd, Z-pack Tinman and Multigig RT connectors, the Minipak HDE high-current power module connector is packaged in a one-piece molded housing designed to allow airflow through the connector to reduce heat build-up. The dual-row configuration provides PCB designers with flexibility in terms of power flow, and offers the additional benefit of occupying half the linear PCB edge space as compared with other types of board-to-board power modules, according to Tyco.

In addition to the new power connector designs, leading connector manufacturers such as FCI and Molex are making it easier for designers to choose the right power connectors for their applications.

Molex, for instance, has rebranded all its power designs over the past year under the EXTreme name, covering many current levels, mechanical envelopes, mating terminations and configurations to address a variety of applications. Meanwhile FCI has launched a Power Solutions microsite which provides information about the company's various power solutions. It also offers a dedicated microsite for its recently launched HCI power distribution connector system to help designers determine which HCI products best fit their designs.

- Gina Roos
EE Times

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