LM3478/LM3478Q High Efficiency Low-Side N-Channel Controller for Switching Regulator
March 30, 2009
LM3478/LM3478Q
High Efficiency Low-Side N-Channel Controller for
Switching Regulator
General Description
The LM3478 is a versatile Low-Side N-Channel MOSFET
controller for switching regulators. It is suitable for use in
topologies requiring a low side MOSFET, such as boost, fly-
back, SEPIC, etc. Moreover, the LM3478 can be operated at
extremely high switching frequency in order to reduce the
overall solution size. The switching frequency of the LM3478
can be adjusted to any value between 100kHz and 1MHz by
using a single external resistor. Current mode control pro-
vides superior bandwidth and transient response, besides
cycle-by-cycle current limiting. Output current can be pro-
grammed with a single external resistor.
The LM3478 has built in features such as thermal shutdown,
short-circuit protection, over voltage protection, etc. Power
saving shutdown mode reduces the total supply current to
5µA and allows power supply sequencing. Internal soft-start
limits the inrush current at start-up.
Features
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LM3478Q is AEC-Q100 qualified and manufactured on an
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Automotive Grade Flow
8-lead Mini-SO8 (MSOP-8) package
Internal push-pull driver with 1A peak current capability
Current limit and thermal shutdown
Frequency compensation optimized with a capacitor and
a resistor
Internal softstart
Current Mode Operation
Undervoltage Lockout with hysteresis
Applications
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Distributed Power Systems
Battery Chargers
Offline Power Supplies
Telecom Power Supplies
Automotive Power Systems
Key Specifications
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Wide supply voltage range of 2.97V to 40V
100kHz to 1MHz Adjustable clock frequency
±2.5% (over temperature) internal reference
10µA shutdown current (over temperature)
Typical Application Circuit
10135501
Typical High Efficiency Step-Up (Boost) Converter
© 2009 National Semiconductor Corporation
101355
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