Three-phase BLDC driver with integrated power loss brake

14th November 2019
Alex Lynn

Allegro MicroSystems has announced the launch a first three-phase BLDC driver IC with integrated power loss brake (PLB) features. The A89331 code-free, sinusoidal sensorless fan driver is designed to improve thermal efficiency, which reduces energy use and data centre costs. The new PLB features also improve safety and reduce the bill of materials (BoM) in the data centre.

“We created the A89331 in direct response to trends in the server market,” explained Andy Wang, Product Line Engineering Manager at Allegro. “It is the smallest yet most advanced solution for server and data centre cooling fans.”

Creating a greener, more energy efficient data centre

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 unique, integrated PLB function in the A89331 applies a brake to fans that aren’t working properly, which eliminates the extra power use and increases thermal efficiency. The end result is lower energy consumption and lower data centre costs.

Simplifying solutions

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

The A89331 is the world’s first and only solution that fits both a three-phase BLDC driver and PLB in a 1U fan. Plus, Allegro’s proprietary code-free drivers eliminate the need for software development and verification. Benefits include better performance, lower BoM cost, smaller footprint, reduced development cost and faster time to market.

Contributing to a safer data centre

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,” added Wang. “We’ve integrated many functions that address market requirements and help our customers improve their own performance.”

The A89331 offers a trapezoidal drive for higher RPMs and improves speed accuracy to ±1.5% @ 25◦C.

A89331 has max input voltage operating rating of 18V with an operating range of -40° to 105°C. It is available in a 28-contact five by five millimetre QFN with exposed thermal pad (suffix ES), and a 20-lead TSSOP with exposed thermal pad (suffix LP). These packages are lead (Pb) free, with 100% matt-tin leadframe plating.

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