Constant On-Time Buck Regulator ICs

April 13, 2006

How did the constant ontime (COT) buck regulator IC evolve? The COT regulator is a modified version of the basic hysteretic regulator shown in Figure 1. The basic hysteretic regulator IC consists of a comparator with input hysteresis that compare

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How did the constant ontime (COT) buck regulator IC evolve?

The COT regulator is a modified version of the basic hysteretic regulator shown in Figure 1. The basic hysteretic regulator IC consists of a comparator with input hysteresis that compares the output feedback voltage with a reference volt turning off the buck switch MOSFET.

When the feedback voltage exceeds the reference voltage, the comparator output goes low, turning off the buck switch MOSFET. The switch remains off until the feedback voltage falls below the reference hysteresis voltage. Then, the comparator output goes high, turning on the switch and allowing the output voltage to rise again.

What are the characteristics of the basic hysteretic buck regulator IC?

It reacts extremely quickly to load and line transients due to itswide bandwidth control loop. Unlike a pulsewidth modulation (PWM) regulator, this loop does not require an error amplifier or frequency compensation.

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About the Author

Sam Davis 2

Sam Davis was the editor-in-chief of Power Electronics Technology magazine and website that is now part of Electronic Design. He has 18 years experience in electronic engineering design and management, six years in public relations and 25 years as a trade press editor. He holds a BSEE from Case-Western Reserve University, and did graduate work at the same school and UCLA. Sam was the editor for PCIM, the predecessor to Power Electronics Technology, from 1984 to 2004. His engineering experience includes circuit and system design for Litton Systems, Bunker-Ramo, Rocketdyne, and Clevite Corporation. Design tasks included analog circuits, display systems, power supplies, underwater ordnance systems, and test systems. He also served as a program manager for a Litton Systems Navy program.

Sam is the author of Computer Data Displays, a book published by Prentice-Hall in the U.S. and Japan in 1969. He also authored the book Managing Electric Vehicle Power. He is also a recipient of the Jesse Neal Award for trade press editorial excellence, and has one patent for naval ship construction that simplifies electronic system integration.

You can also check out additional articles on his other author page.