The LTC3855 is a synchronous buck controller from Linear Technology that can generate high current rails with the accuracy and efficiency to satisfy the most demanding requirements of today’s leading edge network, telecommunications and server applications. It features strong gate drivers that support operation with per-phase currents above 20A, an accurate 0.6V ±0.75% reference, and an integrated differential amplifier (diff amp) that allows remote sensing of the output of critical rails.
This document describes the LTC3855, a two-phase, dual output synchronous buck controller designed to generate high-current rails with accuracy and efficiency. It features strong gate drivers supporting per-phase currents above 20A and an accurate reference allowing remote sensing of critical outputs.
The controller utilizes peak current mode architecture for fast current limiting and real-time current sharing in PolyPhase applications. It supports DCR sensing or sense resistor configurations, includes programmable switching frequencies between 250kHz and 770kHz, and offers options like Burst Mode operation for high efficiency at light loads.
| Output Voltage Range (without diff amp) | 0.6V to 12.5V |
|---|---|
| Output Voltage Range (with diff amp) | 0.6V to 3.3V |
| Per-Phase Current Support | above 20A |
| Reference Accuracy | 0.6V +0.75% |
| Switching Frequency Range | 250kHz to 770kHz |
| Input Voltage Range | up to 38V |
| Minimum On-Time | 100ns typical |
| Full Load Efficiency (1.5V/20A) | 89.5% |
| Package Options | 6mm x 6mm QFN or 38-lead TSSOP |
The output voltage ranges from 0.6V to 12.5V without the differential amplifier, and from 0.6V to 3.3V with it.
Yes, it can sense inductor current using either a sense resistor or inductor DCR sensing.
The switching frequency can be programmed up to 770kHz.
The controller is available in a 6mm x 6mm QFN or a thermally enhanced 38-lead TSSOP package.