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Micrel regulator enables slimmer phones

Posted: 27 Jan 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Micrel? MIC2285? buck regulator?

Micrel Inc. unveiled what it touts as the industry's first 8MHz, 500mA synchronous buck regulator for portable applications.

Merging the best of LDO and buck regulator technology, the MIC2285 regulator is aimed at space-sensitive applications including ultra-thin cellphones, PDAs, GPS systems, digital cameras and portable media players.

"Today's portable applications continue to demand increasingly smaller solution sizes. Cellphone manufacturers in particular, are competing with each other to provide the consumer with the sleekest phones while increasing functionality at the same time," said Ralf Muenster, Micrel's director of marketing for power products. "By using a 470nH chip inductor, Micrel offers designers the only step-down regulator that enables a sub-1mm height solution. This will enable cellphone manufacturers to design more appealing slimmer phones."

The MIC2285 also features ultra-low noise and fast transient response. By incorporating a LOWQ LDO mode, the regulator offers the best of both worlds, said Micrel. Under light load conditions, it can be switched into the LDO mode using a LOWQ pin, offering low noise operation with fast transient response; while at full load, it offers the efficiency of a PWM buck regulator.

Additionally, the MIC2285 consumes 20?A quiescent current in the LDO mode. When the processor wakes up from sleep mode to full power mode, the LDO in the MIC2285 is able to provide the current step required with minimal output capacitance while the switching regulator takes over to power the processor. Other regulators used in the industry today employ a PFM scheme at light loads. While this achieves good light-load efficiency, said Micrel, transient response suffers, resulting in the need for approximately five times the output capacitance in order to achieve a tightly regulated output voltage.

The MIC2285 chip operates from 2.7V to 5.5V input, and features internal power MOSFETs that can supply up to 500mA output current in PWM mode. It can also operate with a maximum duty cycle of 100 percent for use in low dropout conditions.

The MIC2285 is available in the 10-pin 3-by- 3mm MLF package with a junction operating range from -40C to 125C. This regulator is currently available in volume quantities, with pricing starting at $1.50 for 1,000-piece orders.

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