New Industry Products

Multiphase Expander for Synchronous Boost DC-DCs Supports up to 4 Phases

June 13, 2019 by Scott McMahan

Analog Devices released the LT®8551, a multiphase expander for synchronous boost dc-dc converters. It operates together with any synchronous boost dc-dc converter. The device adds extra phases, which are clocked out-of-phase to reduce ripple current and filtering capacitance, increasing the load current capability. The LT8551 operates over a fixed frequency from 100kHz to 1MHz or can be synchronized to an external clock.

Typical applications for the device include high-current distributed power systems, telecom, datacom, automotive, industrial, and storage systems.

According to the company, the multiphase expander easily adds phases without the need to route sensitive control and feedback signals. It expands up to four phases per chip, and it supports up to 80V input or output voltages.

LT8551 integrates 5V gate drivers and can support up to four boost phases per device. Multiple LT8551 devices can be used for up to 18 phases from 20° to 180°, and the phases can share phase angle.

Related: Adjustable Current or Voltage Source DC-DC Reference Design

LT8551 supports bi-directional current flow and features RSENSE or DCR current sensing.

Accurate monitoring and adjustment of the current of each channel achieve excellent dc and transient current sharing. Available in a 52-lead (7mm × 8mm) QFN Package, it can cascade with multiple chips for high-current applications.


  • Expands Up to 4 Phases per Chip
  • Up to 80V Input or Output Voltage
  • Cascade with Multiple Chips for High Current Applications
  • Supports Up to 18 Distinct Phases from 20° to 180°
  • Phases Can Share Phase Angle
  • Excellent DC and Transient Current Sharing
  • Phase-Lockable Fixed Frequency 125kHz to 1MHz
  • Supports Bidirectional Current Flow
  • RSENSE or DCR Current Sensing
  • Eliminates Need to Route Sensitive Feedback and Control Signals.
  • 52-Lead (7mm × 8mm) QFN Package