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Tuesday, February 24, 2009

Switching Regulator by High-Side N-Channel Controller

High Efficiency High-Side N-Channel Controller for
Switching Regulator
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.

- 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

LM3477 Datasheet Pdf

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