LM3477_14 Datasheet, PDF (1/34 Pages) Texas Instruments – High Efficiency High-Side N-Channel Controller for Switching Regulator

LM3477
www.ti.com
SNVS141J – MAY 2004 – REVISED JULY 2004
LM3477 High Efficiency High-Side N-Channel Controller for Switching Regulator
Check for Samples: LM3477
FEATURES
1
•2 500kHz switching frequency
• Adjustable current limit
• 1.5% reference
• Thermal shutdown
• Frequency compensation optimized with a
single capacitor and resistor
• Internal softstart
• Current mode operation
• Undervoltage lockout with hysteresis
• 8-lead Mini-SO8 (MSOP-8) package
APPLICATIONS
• Local Voltage Regulation
• Distributed Power
• Notebook and Palmtop Computers
• Internet Appliances
• Printers and Office Automation
• Battery operated Devices
• Cable Modems
• Battery Chargers
LM3477
LM3477A
Hysteretic Threshold
≊ 36% of programmed
current limit
≊ 12% of programmed
current limit
NOTE
*See Hysteretic Threshold
and section for more
information.
DESCRIPTION
The LM3477/A is a high-side N-channel MOSFET switching regulator controller. It can be used in topologies
requiring a high side MOSFET such as buck, inverting (buck-boost) and zeta regulators. The LM3477/A's internal
push pull driver allows compatibility with a wide range of MOSFETs. This, the wide input voltage range, use of
discrete power components and adjustable current limit allows the LM3477/A to be optimized for a wide variety of
applications.
The LM3477/A uses a high switching frequency of 500kHz to reduce the overall solution size. Current-mode
control requires only a single resistor and capacitor for frequency compensation. The current mode architecture
also yields superior line and load regulation and cycle-by-cycle current limiting. A 5µA shutdown state can be
used for power savings and for power supply sequencing. Other features include internal soft-start and output
over voltage protection. The internal soft-start reduces inrush current. Over voltage protection is a safety feature
to ensure that the output voltage stays within regulation.
The LM3477A is similar to the LM3477. The primary difference between the two is the point at which the device
transitions into hysteretic mode. The hysteretic threshold of the LM3477A is one-third of the LM3477.
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2004, Texas Instruments Incorporated