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Micrel IC reduces input ripple, noise

Posted: 27 Oct 2003 ?? ?Print Version ?Bookmark and Share

Keywords:micrel semiconductor? mic2287? mic2289?

Designed for driving white LEDs in cellphones, PDAs, digital still cameras and camcorder applications, the dc-dc converters from Micrel Semiconductor implement high frequency 1.2MHz PWM control to allow small external components and low noise operation. The constant frequency PWM control of the MIC2287 and MIC2289 reduces input ripple and noise compared to variable-frequency PFM boost converter solutions.

The devices offer a high level of safety with three levels of over-voltage protection (OVP). The OVP feature protects the IC and external components in case of fault conditions which would cause the boost regulator to generate uncontrolled high voltages. The three OVP options of 15-, 24-, and 34V allow customers to use lower cost and smaller size low-voltage rating output capacitors.

The MIC2289 is available in a 2-by-2mm MLF-8L package for $1.22, and requires four external components to provide a complete white LED driver solution. The low component count is achieved by integrating the external Schottky diode normally required with boost regulators.

The MIC2287 is similar to the MIC2289, except it operates with an external Schottky diode. It is suitable for higher power applications that would benefit by sharing the IC power dissipation with an external Schottky diode. The product is available in a 2-by-2mm MLF-8L package for $1.06, as well as in an SOT23-5L package for $1.13.

Both devices operate with a 2.5V to 10V input voltage range, and features a 500mA switch current rating , and their output voltage achieves up to 34V, allowing the MIC2287/9 to power up to 8 white LEDs in series.

Tony Grizelj, marketing manager for power products, said, "The devices achieve over 80 percent efficiency across the Li-ion battery voltage range, saving valuable battery life."

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