AGND

PGND

VIN

EN/UVLO

RON

SS

SW

BST

VCC

FB

FPWM

LM5161

AGND

PGND

VIN

EN/UVLO

RON

SS

SW

BST

VCC

FB

FPWM

LM5161

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An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. PRODUCT PREVIEW Information. Product in design phase of

development. Subject to change or discontinuance without notice.

LM5161

SNVSAE3 – MARCH 2016

LM5161 Wide Input 100-V, 1-A Synchronous Buck/Fly-Buck™ Converter

1

1 Features

1

•

Wide 4.5-V to 100-V Input Voltage Range

•

Integrated High and Low Side Switches

–

No Schottky Diode Required

•

1-A Maximum Load Current

•

Constant On-Time Control

–

No External Loop Compensation

–

Fast Transient Response

•

Selectable DCM Buck Operation at Light Load

•

No External Ripple circuit needed (at FPWM = 0)

•

CCM Option Supports Multi-Output Fly-Buck

•

Nearly Constant Switching Frequency

•

Frequency Adjustable up to 1 MHz

•

Programmable Soft-Start Time

•

Pre-Biased Startup

•

Peak Current Limiting Protection

•

Adjustable Input UVLO and Hysteresis

•

±1% Feedback Voltage Reference

•

Thermal Shutdown Protection

2 Applications

•

Industrial Programmable Logic Controller

•

IGBT Gate Drive Bias Supply

•

Telecom Primary/Secondary Side Bias

•

E-meter Power Line Communication

•

Low Power (<12W) Isolated DC-DC (Fly-Buck)

•

Automotive Electronics

3 Description

The LM5161 is a 100-V, 1-A synchronous step-down

converter with integrated high-side and low-side

MOSFETs. The constant-on-time control scheme

requires no loop compensation and supports high

step-down ratios with fast transient response. An

internal feedback amplifier maintains ±1% output

voltage

regulation

over

the

entire

operating

temperature range. The on-time varies inversely with

input voltage resulting in nearly constant switching

frequency. Peak and valley current limit circuits

protect against overload conditions. The under-

voltage

lockout

(EN/UVLO)

circuit

provides

independently

adjustable

input

under-voltage

threshold

and

hysteresis.

The

LM5161

is

programmed through the FPWM pin to operate in

continuous conduction mode (CCM) from no load to

full load or to automatically switch to discontinuous

conduction mode (DCM) at light load for higher

efficiency. The forced CCM option in the FPWM pin

supports the multiple output and isolated Fly-Buck

applications using a coupled inductor. In addition, the

LM5161 can also be programmed through the FPWM

pin to regulate over load without any additional

external ripple injection circuit.

Device Information(1)

PART NUMBER

PACKAGE

BODY SIZE (NOM)

LM5161

HTSSOP (14)

4.4 mm × 5.0 mm

(1) For all available packages, see the orderable addendum at

the end of the datasheet.

Typical Sync-Buck Application Circuit

Typical Fly-Buck Application Circuit