LM3477_15 Datasheet, PDF (1/35 Pages) Texas Instruments – LM3477 High Efficiency High-Side N-Channel Controller for Switching Regulator

LM3477
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SNVS141K – OCTOBER 2000 – REVISED MARCH 2013
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 (VSSOP-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
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.
LM3477
LM3477A
Hysteretic Threshold⁽¹⁾
≊ 36% of programmed current limit
≊ 12% of programmed current limit
(1) See Hysteretic Threshold and PROGRAMMING THE
CURRENT LIMIT/HYSTERETIC THRESHOLD for more
information.
1
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2
PRODUCTION DATA information is current as of publication date.
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Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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