This document describes the features and functions of a high-accuracy synchronous step-down controller, including output voltage tracking and programmable margining. The controller is suitable for power supply designs for high-performance servers, ASICs, and memory systems. It has a wide operating range and high accuracy, with input voltages ranging from 4V to 32V and output voltages ranging from 0.6V to 2.5V, with a reference voltage accuracy of ±0.67%. The controller uses a constant on-time, valley current mode control architecture, allowing it to operate at very low duty cycles with fast transient response. Additionally, it has an optional current sensing resistor for high efficiency or most accurate current limit.
This document is Design Note 364, which details advanced power supply design techniques using the LTC3770 controller. It focuses on two key functions: output voltage tracking for sequencing multiple supplies and programmable voltage margining for production testing.
The guide explains how to configure the TRACK/SS pin for coincident or ratiometric tracking of another supply, as well as how to use the MARGIN1 and MARGINO pins to adjust the output voltage up or down. It includes circuit examples, efficiency curves, timing diagrams, and resistor selection formulas for setting margining levels.
The LTC3770 is a wide operating range, high accuracy, synchronous step-down DC/DC controller.
The LTC3770 operates with input voltages from 4V to 32V.
The controller uses a highly accurate +0.67% 0.6V reference voltage.
The LTC3770 provides very strong gate drivers allowing up to 25A output currents.