SRM4010
40A Synchronous Rectifier Module
C OL OR AD O DIVISIO N
DESCRIPTION
The SRM4010 Module is a complete
solution for implementing very high
efficiency Synchronous Rectification
and
eliminates many of the problems with self-
driven approaches. The module connects to
the transformer secondary of a Forward
Converter to provide complete high current
rectification at output voltages ranging from 5
volts down to 1.0 volt, in a thermally efficient
surface mount package.
Rectification Efficiency as high as 95%
is
achieved by avoiding cross conduction.
Dedicated Ics provide effective Gate drive of
the ultra low Rds(on) MOSFETs used in the
module. In conventional self-driven
approaches, the MOSFET drive ends as soon
as the power transformer finishes resetting.
This causes increased losses as the duty cycle
decreases. The SRM4010 control circuitry
drives either the Forward or the Catch
MOSFET over virtually the entire duty cycle.
Only a small prediction time, typically 100 ns,
is needed to avoid cross conduction.
The SRM 4010 is designed to handle large
sudden changes in duty cycle.
This makes
the module suitable for current mode control
applications, with large load changes
where high bandwidth is needed. Proprietary
prediction circuitry eliminates cross conduction
for sudden large changes in pulse width. The
module is self-powered from the transformer
secondary winding and operates over a wide
range of peak transformer voltages and PWM
frequencies.
A 5-Volt Linear Regulator
is also available as
a power supply for other secondary side
circuitry such as powering opto coupler
feedback. In very low voltage applications
where the peak transformer voltage is not high
enough for powering the modules, secondary
power can be provided to the regulator from an
additional transformer winding.
The High Current Surface Mount Package
has Low Inductance,
and robust terminals
for superior regulation and low noise
susceptibility in high load current transients.
The Module has an isolated base and is
designed for direct PCB mounting with the
terminals formed within the package. The
base-plate of the module allows heat to be
dissipated by the PCB etch, or a mechanical
sink attachment through the PCB for higher
power applications.
KEY FEATURES
W W W.
Microsemi
.COM
Easy to use Surface Mountable
Solution for up to 40A
Very High Rectification
Efficiency at Output Voltages
from 5V down to 1V
Integrated Solution with few
external parts saves Board
Space
Robust Package with Copper
Base-Plate provides Effective
Heat Distribution
5 Volt Linear Regulator
available to power Secondary
side Circuitry
Suitable for converters that
operate at light load
Avoids problems with parallel
operation that plague simple
self-driven schemes
Operates at PWM Frequencies
ranging from 200 to 400KHz
APPLICATIONS
High Current Isolated DC-DC
Converters
Distributed Power
Architectures
CPU Power Supply off 48VDC
Bus
P R OD UC T H I G H LI GH T
P A C KA GE
V
IN
48 to 150V
V
OUT
1 to 5V
FWD
CTCH
SRM4010
PWM
Controller
SRM4010
5V
REG
PGND
OPTO
Feedback
Figure 1
Copyright 2000
2003-02-05 Rev. IR
Figure 2
Microsemi
Page 1
Colorado Division
800 Hoyt Street, Broomfield, CO. 80020, 303-469-2161, Fax: 303-466-3775
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