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BST

RON

RTN

SW

VCC

FB

UVLO

VIN

VOUT1

VOUT2

D1

X1

LM34927

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D2

9V-100V

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Reference

Design

LM34927

SNVS799G – APRIL 2012 – REVISED DECEMBER 2014

LM34927 Integrated Secondary-Side Bias Regulator for Isolated DC-DC Converters

1 Features

3 Description

The LM34927 regulator features all of the functions

1

•

Wide 7.5-V to 100-V Input Range

needed to implement a low-cost, efficient, isolated

•

Integrated 600-mA High-Side

bias regulator. This high-voltage regulator contains

and Low-Side Switches

two 100-V N-channel MOSFET switches — a high-

•

No Schottky Required

side buck switch and a low-side synchronous switch.

The

Constant

on-time

(COT)

control

scheme

•

Constant On-Time Control

employed in the LM34927 device requires no loop

•

No Loop Compensation Required

compensation

and

provides

excellent

transient

•

Ultra-Fast Transient Response

response. The regulator operates with an on-time that

is inversely proportional to the input voltage. This

•

Nearly Constant Operating Frequency

feature allows the operating frequency to remain

•

Intelligent Peak Current Limit

relatively constant. An intelligent peak current limit is

•

Adjustable Output Voltage From 1.225 V

implemented with integrated sense circuit. Other

•

Precision 2% Feedback Reference

features include a programmable input undervoltage

comparator to inhibit operation during low-voltage

•

Frequency Adjustable to 1 MHz

conditions.

Protection

features

include

thermal

•

Adjustable Undervoltage Lockout (UVLO)

•

Remote Shutdown

The LM34927 device is offered in WSON-8 and SO

PowerPAD-8 plastic packages.

•

Thermal Shutdown

•

Packages:

Device Information(1)

–

WSON-8

PART NUMBER

PACKAGE

BODY SIZE (NOM)

–

SO PowerPAD™-8

SO PowerPAD (8)

4.89 mm x 3.90 mm

LM34927

WSON (8)

4.00 mm x 4.00 mm

2 Applications

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

•

Isolated Telecom Bias Supply

the end of the data sheet.

•

Isolated Automotive and Industrial Electronics

Typical Application

1

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. PRODUCTION DATA.