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 500mA load current with excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5.0V, 12V, and an adjustable output version.

Requiring a minimum number of external components, these regulators are simple to use and include patented internal frequency compensation (Patent Nos. 5,382,918 and 5,514,947), 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 would be needed 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 needed.

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 datasheet 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 stand-by current. The output switch includes current limiting, as well as thermal shutdown for full protection under fault conditions.

To simplify the LM2671 buck regulator design procedure, there exists computer design software, (version 6.0).

• Efficiency up to 96%
• Available in SOIC, 8-pin PDIP and WSON Packages
• Computer Design Software (version 6.0)
• Simple and Easy to Design With
• Requires Only 5 external Components
• Uses Readily Available Standard Inductors
• 3.3V, 5.0V, 12V, and Adjustable Output Versions
• Adjustable Version Output Voltage Range: 1.21V to 37V
• ±1.5% Max Output Voltage Tolerance Over Line and Load Conditions
• Ensured 500mA Output Load Current
• 0.25? DMOS Output Switch
• Wide Input Voltage Range: 8V to 40V
• 260 kHz Fixed Frequency Internal Oscillator
• TTL Shutdown Capability, Low Power Standby Mode
• Soft-Start and Frequency Synchronization
• Thermal Shutdown and Current Limit Protection

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