January 16, 2008
LM20133
3A, PowerWise® Synchronous Buck Regulator with Input
Synchronization
General Description
Features
The LM20133 is a full featured synchronous buck regulator
capable of delivering up to 3A of continuous output current.
The current mode control loop can be compensated to be
stable with virtually any type of output capacitor. For most
cases, compensating the device only requires two external
components, providing maximum flexibility and ease of use.
The device is optimized to work over the input voltage range
of 2.95V to 5.5V making it suited for a wide variety of low volt-
age systems.
Input voltage range 2.95V to 5.5V
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Accurate current limit minimizes inductor size
97% peak efficiency
Frequency synchronization pin
32 mΩ integrated FET switches
Starts up into pre-biased loads
Output voltage tracking
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Peak current mode control
The device features internal over voltage protection (OVP)
and over current protection (OCP) circuits for increased sys-
tem reliability. A precision enable pin and integrated UVLO
allows the turn on of the device to be tightly controlled and
sequenced. Start-up inrush currents are limited by both an
internally fixed and externally adjustable Soft-Start circuit.
Fault detection and supply sequencing is possible with the
integrated power good circuit.
Adjustable Soft-Start with external capacitor
Precision enable pin with hysteresis
Integrated OVP, UVLO, power good and thermal
shutdown
eTSSOP-16 exposed pad package
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Applications
The switching frequency of the LM20133 can be synchro-
nized to an external clock by use of the SYNC pin. The SYNC
pin is capable of synchronizing to input signals ranging from
500 kHz to 1.5 MHz.
Simple to design, high efficiency point of load regulation
from a 5V or 3.3V bus
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High Performance DSPs, FPGAs, ASICs and
microprocessors
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The LM20133 is designed to work well in multi-rail power
supply architectures. The output voltage of the device can be
configured to track a higher voltage rail using the SS/TRK pin.
If the output of the LM20133 is pre-biased at startup it will not
sink current to pull the output low until the internal soft-start
ramp exceeds the voltage at the feedback pin.
Broadband, Networking and Optical Communications
Infrastructure
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The LM20133 is offered in a 16-pin eTSSOP package with an
exposed pad that can be soldered to the PCB, eliminating the
need for bulky heatsinks.
Typical Application Circuit
30030301
®
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© 2008 National Semiconductor Corporation
300303
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