Main

Output

3.3V

FB

AGND

COMP

Sync

SS

HB

HO

HS

LO

PGND

CO

CS

RAMP

LM5115

Auxiliary

Output

2.0V

+12V

FEEDBACK

Main Converter

PWM Controller

INPUT

Phase Signal

LM5115

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SNVS343E – MARCH 2005 – REVISED MARCH 2013

LM5115 Secondary Side Post Regulator / Synchronous Buck Controller

Check for Samples: LM5115

1

FEATURES

DESCRIPTION

The

LM5115

is

a

versatile

switching

regulator

2

•

Self-Synchronization to Main Channel Output

controller. It has two main application configurations.

•

Standalone DC/DC Synchronous Buck Mode

The first is utilizing the Secondary Side Post

•

Leading Edge Pulse Width Modulation

Regulation (SSPR) technique to implement multiple

output power converters. In the second configuration,

•

Voltage-Mode Control with Current Injection

it can be used as a standalone synchronous buck

and Input Line Feed-Forward

controller

(Please

see

Standalone

DC/DC

•

Operates from AC or DC Input up to 75V

Synchronous Buck Mode for more details). The

•

Wide 4.5V to 30V Bias Supply Range

SSPR technique develops a highly efficient and well

regulated auxiliary output from the secondary side

•

Wide 0.75V to 13.5V Output Range.

switching waveform of an isolated power converter.

•

Top and Bottom Gate Drivers Sink 2.5A Peak

Regulation of the auxiliary output voltage is achieved

•

Adaptive Gate Driver Dead-Time Control

by leading edge pulse width modulation (PWM) of the

main channel duty cycle. Leading edge modulation is

•

Wide Bandwidth Error Amplifier (4MHz)

compatible with either current mode or voltage mode

•

Programmable Soft-Start

control of the main output. The LM5115 drives

•

Thermal Shutdown Protection

external high side and low side NMOS power

switches configured as a synchronous buck regulator.

•

TSSOP-16 or Thermally Enhanced WSON-16

A

current

sense

amplifier

provides

overload

Packages

protection and operates over a wide common mode

input range. Additional features include a low dropout

(LDO)

bias

regulator,

error

amplifier,

precision

reference, adaptive dead time control of the gate

signals and thermal shutdown.

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.