LM5115_14 Datasheet, PDF (1/24 Pages) Texas Instruments – Secondary Side Post Regulator / Synchronous Buck Controller

LM5115
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SNVS343D – MARCH 2005 – REVISED JULY 2006
LM5115 Secondary Side Post Regulator / Synchronous Buck Controller
Check for Samples: LM5115
FEATURES
1
•2 Self-synchronization to main channel output
• Standalone DC/DC Synchronous buck mode
• Leading edge pulse width modulation
• Voltage-mode control with current injection
and input line feed-forward
• Operates from AC or DC input up to 75V
• Wide 4.5V to 30V bias supply range
• Wide 0.75V to 13.5V output range.
• Top and bottom gate drivers sink 2.5A peak
• Adaptive gate driver dead-time control
• Wide bandwidth error amplifier (4MHz)
• Programmable soft-start
• Thermal shutdown protection
• TSSOP-16 or thermally enhanced LLP-16
packages
DESCRIPTION
The LM5115 is a versatile switching regulator controller. It has two main application configurations. The first is
utilizing the Secondary Side Post Regulation (SSPR) technique to implement multiple output power converters. In
the second configuration, it can be used as a standalone synchronous buck controller (Please see page 14 for
more details). The SSPR technique develops a highly efficient and well regulated auxiliary output from the
secondary side switching waveform of an isolated power converter. Regulation of the auxiliary output voltage is
achieved by leading edge pulse width modulation (PWM) of the main channel duty cycle. Leading edge
modulation is compatible with either current mode or voltage mode control of the main output. The LM5115
drives external high side and low side NMOS power switches configured as a synchronous buck regulator. A
current sense amplifier provides overload 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
INPUT
FEEDBACK
Main Converter
PWM Controller
Phase Signal
Main
Output
3.3V
+12V
V_CC ^Sync HB
LM5115
V_BIAS
HO
RAMP
HS
SS
LO
CO
COMP
CS
FB
V_OUT
PGND AGND
R_S
Auxiliary
Output
2.0V
Figure 1. Simplified Multiple Output Power Converter Utilizing SSPR Technique
1
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2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2005–2006, Texas Instruments Incorporated