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ADI LT8550 Four-Phase DC-DC Expander for Synchronous Buck DC-DC Converters

November 15, 2019 by Luke James

LT8550 4-Phase DC-DC Expander is a multi-phase expander for synchronous buck DC/DC converters. The expander operates with any other buck DC-DC converter to increase load current capability.

This multi-phase expander for synchronous buck DC-DC converters works in tandem with any buck DC-DC converter to improve load current ability through the addition of extra phases that are clocked out-of-phase to lessen ripple current and filtering capacitance. 


LT8550 Primary Product Details

Operating over a fixed frequency from 125 kHz to 1 MHz, the LT8550 integrates gate drivers and can support up to four buck phases per device. Multiple LT8550 expanders can be used together for up to 18 individual phases. The expander can be used to monitor and adjust the current of each channel to achieve the best DC and transient current sharing. 


10V/100A step-down phase expander system

10V/100A step-down phase expander system. Image courtesy of Analog Devices Inc.

Additional Product Features to Consider

Other features of the LT8550 include up to 80V input or output voltage, phase-lockable fixed frequency of 125 kHz to 1 MHz, support for bidirectional current flow, RESENSE or DCR current sensing, and the ability for phases to share a phase angle. The expander comes in a 52-Lead (7mm x 8mm) QFN package, it eliminates the need to route sensitive feedback and control signals, and it can be synchronized to an external clock. 

Proprietary control architecture enables the LT8550 to cycle-by-cycle duplicate the operation of a buck controller. It also measures the primary controller’s inductor current in addition to its gate driver operation timing, and at the same time, accurately monitors and adjusts the current of each expanded channel for optimal DC and transient current sharing. 

Typical applications for the LT8550 include high current distributed power systems, telecommunication, datacomms, storage systems, general industry, and automotive. 

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