LM3477MM National Semiconductor, LM3477MM Datasheet
LM3477MM
Manufacturer Part Number
LM3477MM
Description
Pulse Width Modulation (PWM) Controller IC
Manufacturer
National Semiconductor
Specifications of LM3477MM
Input Voltage Primary Min
2.95V
Mounting Type
Surface Mount
Topology
Buck (Step Down)
Control Mode
Current
Duty Cycle Max
93%
Input Voltage Primary Max
35V
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Available stocks
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Price
Part Number:
LM3477MM
Manufacturer:
NS/国半
Quantity:
20 000
Part Number:
LM3477MM/NOPB
Manufacturer:
NS/国半
Quantity:
20 000
Part Number:
LM3477MMX
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NS/国半
Quantity:
20 000
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Part Number:
LM3477MMX/NOPB
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TI
Quantity:
6 223
© 2004 National Semiconductor Corporation
LM3477
High Efficiency High-Side N-Channel Controller for
Switching Regulator
General 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 opti-
mized 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 re-
quires 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 sav-
ings and for power supply sequencing. Other features in-
clude 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 volt-
age stays within regulation.
The LM3477A is similar to the LM3477. The primary differ-
ence 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.
Features
n 500kHz switching frequency
n Adjustable current limit
n 1.5% reference
Typical Application Circuit
Typical High Efficiency Step-Down (Buck) Converter
DS200033
n Thermal shutdown
n Frequency compensation optimized with a single
n Internal softstart
n Current mode operation
n Undervoltage lockout with hysteresis
n 8-lead Mini-SO8 (MSOP-8) package
Applications
n Local Voltage Regulation
n Distributed Power
n Notebook and Palmtop Computers
n Internet Appliances
n Printers and Office Automation
n Battery operated Devices
n Cable Modems
n Battery Chargers
capacitor and resistor
*See Hysteretic Threshold and section for more information.
LM3477A
LM3477
20003333
Hysteretic
Threshold
) 36% of
programmed current
limit
) 12% of
programmed current
limit
www.national.com
July 2004
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