7.1 Overview

The LM5161-Q1 step-down switching regulator features all the functions needed to implement a low-cost, efficient buck converter capable of supplying 1-A to the load. This high voltage regulator contains 100-V N-channel buck and synchronous rectifier switches and is available in the 14-pin HTSSOP package. The regulator operation is based on constant ON-time control where the ON-time is inversely proportional to input voltage V_IN. This feature maintains a relatively constant operating frequency with load and input voltage variations. A constant on-time switching regulator requires no loop compensation resulting in fast load transient response. Peak current limit detection circuit is implemented with a forced OFF-time during current limiting which is inversely proportional to voltage at the feedback pin, V_FB and directly proportional to V_IN. Varying the current limit OFF-time with V_FB and V_IN ensures short circuit protection with minimal current limit foldback. The LM5161-Q1 can be applied in numerous end equipment systems requiring efficient step-down regulation from higher input voltages. This regulator is well suited for 24 V industrial systems as well as for 48 V telecom and PoE voltage ranges. The LM5161-Q1 integrates an undervoltage lockout (EN/UVLO) circuit to prevent faulty operation of the device at low input voltages and features intelligent current limit and thermal shutdown to protect the device during overload or short circuit.

All instances of the LM5161 device name used throughout this document, in block diagrams and application schematics, are valid for LM5161-Q1 as well, unless stated otherwise.