SNVS343E – MARCH 2005 – REVISED MARCH 2013
LM5115 Secondary Side Post Regulator / Synchronous Buck Controller
Check for Samples: LM5115
•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 WSON-16
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 Standalone DC/DC
Synchronous Buck Mode 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
VCC Sync HB
Figure 1. Simplified Multiple Output Power Converter Utilizing SSPR Technique
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