BLDC fan driver lowers data centre energy use

Claimed to be the first three-phase brushless direct current (BLDC) driver with integrated power loss brake, the A89331 is a code-free, sinusoidal sensorless fan driver from Allegro Microsystems. It is designed to improve thermal efficiency, which reduces energy use and data centre costs, says Allego. The power loss brake is also claimed to improve safety and reduce the bill of materials (BoM).

Andy Wang, product line engineering manager at Allegro, said: “It is the smallest, yet most advanced solution, for server and data centre cooling fans.”

The A89331 has been introduced because when server fans malfunction or break, backflow causes them to go into reverse rotation. The other fans have to work harder to compensate for the resulting airflow, which increases power consumption. The integrated power loss brake function applies a brake to fans that are not working properly, which eliminates the extra power use and increases thermal efficiency, explains Allegro.

The traditional solution to preventing reverse rotation of broken fans is adding external circuitry to function as the power loss brake, however these external components do not fit into 1U fans, forcing up the BoM cost and lowering efficiency. This approach also requires coding, which increases time-to-market.

The A89331 is believed to be only solution that fits both a three-phase BLDC driver and power loss brake in a 1U fan. An added advantage is that Allegro’s proprietary code-free drivers eliminate the need for software development and verification.

A89331’s integrated power loss brake also stops fans from spinning when they are disconnected from power to prevent injury.

“On top of all of these advancements, the A89331 is designed to run server fans at higher speeds and improve speed control accuracy,” said Wang

The A89331 offers a trapezoidal drive for higher RPMs and improves speed accuracy to ±1.5 per cent at 25 degrees C.

A89331 has maximum input voltage operating rating of 18V with an operating range of -40 to 105 degrees C.  It is available in a 28-contact 5.0 x 5.0mm QFN with exposed thermal pad (suffix ES), and a 20-lead TSSOP with exposed thermal pad (suffix LP). Both packages are lead (Pb) -free, with 100 per cent matt-tin leadframe plating.

http://www.allegromicro.com

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