Designing AI accelerator cards with currents over 1000A

October 09, 2020 //By Nick Flaherty
Designing AI accelerator cards with currents over 1000A
The move to 48V voltages and currents over 1000A on data centre AI accelerator cards is dramatically changing the power architectures.

The latest AI accelerator cards for the data centre such as Nvidia’s A100 card and the Open Compute Project are rapidly moving to 48V and over 1000A of current, challenging the power management requirements, both for the chip and the board designs. A new power architecture and both lateral and vertical packages are needed to power the boards.

“We support an accelerator card that’s very similar to the Nvidia card,” said Robert Gendron, Corporate Vice President for Product Marketing & Technical Resources at Vicor. “We support delivery for the AI processor itself – if you look at the card, there are three chips, with one supporting the primary rail. There’s two other devices for the memory and the other rails of the processor,” he said.

The high current requirements means existing multiphase point of load converters powering the primary rail have run out of steam, he says.

“Customers use us for these AI accelerator cards and the OCP cards, so we designed the chipset specifically to fit an AI accelerator card where the power required exceeds that of what a multiphase could accommodate,” he said. “It would consume too much area and too much loss, transmitting the current from the voltage rail to the processor and the noise contribution would be challenging for a conventional multiphase converter.

Vicor lateral power daigram
Lateral power MCM power for AI boards requiring 400 to 1000A

“We use a different architecture to support 400A and above, and different packaging style to create the high density module. This Factorised Power Architecture does not use a series of inductors to supply current to the processor. Our solution has almost no energy stored within the device so its much smaller and provides better noise and transient performance. We do use a magnetic structure, a magnetic core, that provides and voltage division and current multiplication." 

Next: Vertical power for AI accelerator cards

Vertical power MCM for AI boards requiring over 1000A

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