Integrated LDO Regulator Suits High-End Audio Portables

March 29, 2004
From an input supply of 3 to 5.5 V, the CM3702 integrated charge pump and linear low-dropout (LDO) regulator delivers 5 V to the analog input of a system's audio codec. The device, targeting high-quality audio applications, integrates a charge pump...

From an input supply of 3 to 5.5 V, the CM3702 integrated charge pump and linear low-dropout (LDO) regulator delivers 5 V to the analog input of a system's audio codec. The device, targeting high-quality audio applications, integrates a charge pump that boosts the voltage before feeding it to an internal LDO linear regulator. Also, the charge pump can be used with an external regulator.

The CM3702 maintains a nominal 0.8-V differential between the input and the output of the LDO regulator, leading to a power-supply ripple rejection (PSRR) of 42 dB across the audio band. It provides up to 200 mA of continuous output current at a nominal 5-V output. Typical operating current is 180 µA.

Dual Enable pins permit separate control of charge pump and LDO circuits for faster startup from sleep states. Overload current limiting and over-temperature thermal shutdown are provided.

The charge pump works with two external stable capacitors. It operates at 250 kHz, well outside the audible frequency band. Separate ground pins for the charge pump and the rest of the circuitry eliminate ground-noise feed-through from the charge pump to the regulated output. A bandgap reference bypass pin further minimizes noise.

The CM3702 is sampling along with evaluation boards. Housed in a 10-pin lead-free MSOP package, the LDO costs $0.57 each in 10,000-unit lots. Volume production is scheduled for this quarter.

California Micro Deviceswww.calmicro.com (800) 325-4966

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About the Author

Roger Allan

Roger Allan is an electronics journalism veteran, and served as Electronic Design's Executive Editor for 15 of those years. He has covered just about every technology beat from semiconductors, components, packaging and power devices, to communications, test and measurement, automotive electronics, robotics, medical electronics, military electronics, robotics, and industrial electronics. His specialties include MEMS and nanoelectronics technologies. He is a contributor to the McGraw Hill Annual Encyclopedia of Science and Technology. He is also a Life Senior Member of the IEEE and holds a BSEE from New York University's School of Engineering and Science. Roger has worked for major electronics magazines besides Electronic Design, including the IEEE Spectrum, Electronics, EDN, Electronic Products, and the British New Scientist. He also has working experience in the electronics industry as a design engineer in filters, power supplies and control systems.

After his retirement from Electronic Design Magazine, He has been extensively contributing articles for Penton’s Electronic Design, Power Electronics Technology, Energy Efficiency and Technology (EE&T) and Microwaves RF Magazine, covering all of the aforementioned electronics segments as well as energy efficiency, harvesting and related technologies. He has also contributed articles to other electronics technology magazines worldwide.

He is a “jack of all trades and a master in leading-edge technologies” like MEMS, nanolectronics, autonomous vehicles, artificial intelligence, military electronics, biometrics, implantable medical devices, and energy harvesting and related technologies.

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