LM3000 Datasheet, PDF (1/26 Pages) National Semiconductor (TI) – Dual Synchronous Emulated Current-Mode Controller

LM3000
July 2, 2009
Dual Synchronous Emulated Current-Mode Controller
General Description
The LM3000 is a dual output synchronous buck controller
which is designed to convert input voltages ranging from 3.3V
to 18.5V down to output voltages as low as 0.6V. The two
outputs switch at a constant programmable frequency of 200
kHz to 1.5 MHz, with the second output 180 degrees out of
phase from the first to minimize the input filter requirements.
The switching frequency can also be phase locked to an ex-
ternal frequency. A CLKOUT provides an external clock 90
degrees out of phase with the main clock so that a second
chip can be run out of phase with the main chip. The emulated
current-mode control utilizes bottom side FET sensing to pro-
vide fast transient response and current limit without the need
for external current sense resistors or RC networks. Separate
Enable, Soft-Start and Track pins allow each output to be
controlled independently to provide maximum flexibility in de-
signing system power sequencing.
The LM3000 has a full range of protection features which in-
clude input under-voltage lock-out (UVLO), power good
(PGOOD) signals for each output, over-voltage crowbar and
hiccup mode during short circuit events.
Features
■ ^V_IN ^{range from 3.3V to 18.5V}
■ ^{Output voltage from 0.6V to 80% of V}_IN
■ ^{Remote differential output voltage sensing}
■ ^{1% accuracy at FB pin}
■ ^{Interleaved operation reduces input capacitors}
■ ^{Frequency sync/adjust from 200 kHz to 1.5 MHz}
■ ^{Startup with pre-bias load}
■ ^{Independent power good, enable, soft-start and track}
■ ^{Programmable current limit without external sense resistor}
■ ^{Hiccup mode short circuit protection}
Applications
■ ^{DC Power Distribution Systems}
■ ^{Graphic Cards - GPU and Memory ICs}
■ ^{FPGA, CPLD, and ASICs}
■ ^{Embedded Processor}
■ ^{1.8V and 2.5V I/O Supplies}
■ ^{Networking Equipment (Routers, Hubs)}
Simplified Application
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