Main

Output

3.3V

FB

AGND

COMP

Sync

SS

HB

HO

HS

LO

PGND

CO

CS

RAMP

Auxiliary

Output

2.0V

+12V

FEEDBACK

Main Converter

PWM Controller

INPUT

Phase Signal

LM25115

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SNVS418A – NOVEMBER 2005 – REVISED APRIL 2013

LM25115 Secondary Side Post Regulator Controller

Check for Samples: LM25115

1

FEATURES

DESCRIPTION

The LM25115 controller contains all of the features

2

•

Self-synchronization to Main Channel Output

necessary

to

implement

multiple

output

power

•

Free-run Mode for Buck Regulation of DC

converters

utilizing

the

Secondary

Side

Post

Input

Regulation (SSPR) technique. The SSPR technique

•

Leading Edge Pulse Width Modulation

develops a highly efficient and well regulated auxiliary

output from the secondary side switching waveform of

•

Voltage-mode Control with Current Injection

an isolated power converter. Regulation of the

and Input Line Feed-forward

auxiliary output voltage is achieved by leading edge

•

Operates from AC or DC Input up to 42V

pulse width modulation (PWM) of the main channel

•

Wide 4.5V to 30V Bias Supply Range

duty cycle. Leading edge modulation is compatible

with either current mode or voltage mode control of

•

Wide 0.75V to 13.5V Output Range.

the main output. The LM25115 drives external high

•

Top and Bottom Gate Drivers Sink 2.5A Peak

side and low side NMOS power switches configured

•

Adaptive Gate Driver Dead-time Control

as a synchronous buck regulator. A current sense

amplifier provides overload protection and operates

•

Wide Bandwidth Error Amplifier (4MHz)

over a wide common mode input range. Additional

•

Programmable Soft-start

features include a low dropout (LDO) bias regulator,

•

Thermal Shutdown Protection

error amplifier, precision reference, adaptive dead

time

control

of

the

gate

signals

and

thermal

•

TSSOP-16 or Thermally Enhanced WSON-16

shutdown.

Packages

Typical Application Circuit

Figure 1. Simplified Multiple Output Power Converter Utilizing SSPR Technique

1

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2

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PRODUCTION DATA information is current as of publication date.

Copyright © 2005–2013, Texas Instruments Incorporated

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.