LM3743 Datasheet, PDF (1/23 Pages) National Semiconductor (TI) – N-Channel FET Synchronous Buck Controller for Low Output Voltages

September 2006
LM3743
N-Channel FET Synchronous Buck Controller for Low
Output Voltages
General Description
The LM3743 is a voltage mode PWM buck controller which
implements synchronous rectification. It provides a low cost,
fault tolerant, and efficient point of load solution. To reduce
component count several parameters are fixed, such as
switching frequency and the short circuit protection level. For
example the LM3743 has an operating switching frequency
of 300 kHz or 1 MHz and a fixed 500 mV high side current
limit for switch node short-circuit protection. LM3743 is a
very fault tolerant IC with switch node short-circuit, output
undervoltage protection, and the ability to self recover after
the removal of the fault. It avoids the need to over design
components due to thermal runaway during a fault condition,
thus resulting in a lower cost solution. It employs a propri-
etary monotonic glitch free pre-bias start-up method suited
for FPGAs and ASIC logic devices. A 0.8V internal reference
with ±1.75% accuracy is ideal for sub-volt conversion. An
external programmable soft-start allows for tracking and tim-
ing flexibility. The driver features 1.6Ω of pull-up resistance
and 1Ω of pull-down drive resistance for high power density
and very efficient power processing.
Features
n Input voltage from 3.0V to 5.5V
n Output voltage adjustable down to 0.8V
n Reference accuracy: ±1.75%, over full temperature and
input voltage range
n Low-side sensing programmable current limit
n Fixed high-side sensing for supplemental short-circuit
protection
n Undervoltage protection
n Hiccup mode protection eliminates thermal runaway
during fault conditions
n Externally programmable soft-start with tracking
capability
n Switching frequency options of 1 MHz or 300 kHz
n Pre-bias start-up capability
n MSOP-10 package
Applications
n ASIC/FPGA/DSP core power
n Broadband Communications
n Multi-media Set Top Boxes
n Networking Equipment
n Printers/Scanners
n Servers
n Low Voltage Distributed Power
Typical Application
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