Micrel’s MIC2285 Merges LDO And Buck Regulators

Micrel Inc. has launched the MIC2285, an 8 MHz, 500mA synchronous buck regulator for portable applications. Merging LDO and buck regulator technology, this solution is aimed at space-sensitive applications including ultra-thin cell phones, PDAs, GPS systems, digital cameras, and portable media players.

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

Besides its small size, the MIC2285 high efficiency solution also features ultra-low noise and fast transient response. By incorporating a LOWQTM LDO mode, the MIC2285 offers the best of both worlds, according to a company statement. 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 loads it offers the efficiency of a PWM buck regulator.

In portable applications, the processor consumes a minimal current during sleep mode. In the LDO mode, the MIC2285 offers good efficiency since it consumes a mere 20µA quiescent current. 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 commonly used in the industry today employ a PFM scheme at light loads. While this achieves good light-load efficiency, transient response can suffer, resulting in the need for approximately five times the output capacitance in order to achieve a tightly regulated output voltage. This not only increases the cost of the design, but also results in a larger solution.

The IC 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 3mm x 3mm MLF™ package with a junction operating range from –40°C to +125°C.

This IC is currently available in volume with pricing starting at $1.50 for 1K quantities.