Texas Instruments UCC2897A Evaluation Module UCC2897AEVM UCC2897AEVM 데이터 시트
제품 코드
UCC2897AEVM
User's Guide
SLUU357 – November 2009
48-V to 3.3-V Forward Converter with Active Clamp Reset
Using the UCC2897A Active Clamp Current Mode
PWM Controller
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Introduction
The UCC2897A evaluation module (EVM) is an active clamp reset forward converter providing a 3.3-V
regulated output at 30 A of load current, operating from a 48-V input. The design operates over the full
36-V to 72-V telecom input range, and is able to fully regulate down to zero load current. The module uses
the UCC2897A Current Mode Active Clamp PWM Controller for effectively demonstrating the active clamp
transformer reset technique.
regulated output at 30 A of load current, operating from a 48-V input. The design operates over the full
36-V to 72-V telecom input range, and is able to fully regulate down to zero load current. The module uses
the UCC2897A Current Mode Active Clamp PWM Controller for effectively demonstrating the active clamp
transformer reset technique.
Benefits of the active clamp include a control driven transformer reset scheme allowing zero voltage
switching (ZVS) to increase overall efficiency, lower drain-to-source voltage stress, extended duty cycle
beyond 50% and reduced electromagnetic radiated emissions. Combined with synchronous rectification,
the design operates at 250 kHz and exhibits a peak efficiency of 93%, with a full load efficiency of over
91%. The design displays many features that might be typical of a more complex design, yet its compact
board layout and low component count make it elegantly simple
switching (ZVS) to increase overall efficiency, lower drain-to-source voltage stress, extended duty cycle
beyond 50% and reduced electromagnetic radiated emissions. Combined with synchronous rectification,
the design operates at 250 kHz and exhibits a peak efficiency of 93%, with a full load efficiency of over
91%. The design displays many features that might be typical of a more complex design, yet its compact
board layout and low component count make it elegantly simple
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Description
The UCC2897A controller provides advanced active clamp control features such as programmable
maximum duty cycle clamp, programmable dead time between the two primary switches and the ability to
drive a P-channel MOSFET in a low-side active clamp configuration. The UCC2897A also allows the
ability to start-up directly from the 48-V telecom bus voltage, eliminating the need for external start-up
circuitry. It includes programmable soft start, internal slope compensation for peak current mode control,
internal low-line and high-line voltage sensing, internal bi-directional synchronizable clock input,
cycle-by-cycle current limiting and short circuit current protection, and a robust 2-A sink/source
TrueDrive™ internal gate drive circuit. The result is a highly efficient design loaded with features, requiring
very few external components.
maximum duty cycle clamp, programmable dead time between the two primary switches and the ability to
drive a P-channel MOSFET in a low-side active clamp configuration. The UCC2897A also allows the
ability to start-up directly from the 48-V telecom bus voltage, eliminating the need for external start-up
circuitry. It includes programmable soft start, internal slope compensation for peak current mode control,
internal low-line and high-line voltage sensing, internal bi-directional synchronizable clock input,
cycle-by-cycle current limiting and short circuit current protection, and a robust 2-A sink/source
TrueDrive™ internal gate drive circuit. The result is a highly efficient design loaded with features, requiring
very few external components.
The TrueDrive™ output architecture of UCC2897A uses TI’s unique TrueDrive™ Bipolar/CMOS hybrid
output. To the user, this simply means ultra-fast rise and fall times by providing the highest possible drive
current where it is needed most, at the MOSFET Miller plateau region.
output. To the user, this simply means ultra-fast rise and fall times by providing the highest possible drive
current where it is needed most, at the MOSFET Miller plateau region.
The UCC2897A is available in a 20-pin TSSOP package for applications where absolute minimal board
space is required.
space is required.
The UUCC2897A-EVM highlights the many benefits of using the UCC2897A Active Clamp Current Mode
PWM Controller. The following user guide provides the schematic, component list, assembly drawing,
artwork and test set up necessary to evaluate the UCC2897A in a typical telecom application.
PWM Controller. The following user guide provides the schematic, component list, assembly drawing,
artwork and test set up necessary to evaluate the UCC2897A in a typical telecom application.
The user should note that overcurrent protection is not incorporated in this design.
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48-V to 3.3-V Forward Converter with Active Clamp Reset —Using the
SLUU357 – November 2009
UCC2897A Active Clamp Current Mode —PWM Controller
Copyright © 2009, Texas Instruments Incorporated