The LM2671 series of regulators are monolithic integrated circuits built with a LMDMOS
process. These regulators provide all the active functions for a step-down (buck) switching
regulator, capable of driving a 500-mA load current with excellent line and load regulation. These
devices are available in fixed output voltages of 3.3 V, 5 V, 12 V, and an adjustable output
Requiring a minimum number of external components, these regulators are simple to use and
include patented internal frequency compensation, fixed frequency oscillator, external shutdown,
soft start, and frequency synchronization.
The LM2671 series operates at a switching frequency of 260 kHz, thus allowing smaller
sized filter components than what is required with lower frequency switching regulators. Because of
its very high efficiency (> 90%), the copper traces on the printed-circuit board are the only
heat sinking required.
A family of standard inductors for use with the LM2671 are available from several
different manufacturers. This feature greatly simplifies the design of switch-mode power supplies
using these advanced ICs. Also included in the data sheet are selector guides for diodes and
capacitors designed to work in switch-mode power supplies.
Other features include a ensured ±1.5% tolerance on output voltage within specified input
voltages and output load conditions, and ±10% on the oscillator frequency. External shutdown is
included, featuring typically 50-µA standby current. The output switch includes current limiting,
as well as thermal shutdown for full protection under fault conditions.
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