MIC2285A 8MHz PWM Synchronous Buck Regulator with LDO Standby Mode General Description Features The Micrel MIC2285A is a high efficiency 8MHz 2.7 to 5.5V supply/input voltage PWM synchronous buck (step-down) regulator that Light load LOWQ LDO mode features a LOWQ LDO standby mode that draws 20A quiescent current only 20A of quiescent current. The MIC2285A Low noise, 75Vrms allows an ultra-low noise, small size, and high 8MHz PWM mode efficiency solution for portable power applications. Output current to 600mA In PWM mode, the MIC2285A operates with a >90% efficiency constant frequency 8MHz PWM control. Under light load conditions, such as in system sleep or standby 100% maximum duty cycle modes, the PWM switching operation can be Adjustable output voltage option down to 1V disabled to reduce switching losses. In this light load Fixed output voltage options available LOWQ mode, the LDO maintains the output voltage Ultra-fast transient response and draws only 18A of quiescent current. The LDO mode of operation saves battery life while not Requires only a 0.47H inductor introducing spurious noise and high ripple as Enables sub 0.55mm profile solution experienced with pulse skipping or bursting mode Fully integrated MOSFET switches regulators. Micropower shutdown The MIC2285A operates from 2.7V to 5.5V input and Thermal shutdown and current limit protection features internal power MOSFETs that can supply 10-pin 2mm x 2mm x 0.55mm MLF package up to 600mA output current in PWM mode. It can operate with a maximum duty cycle of 100% for use 40C to +125C junction temperature range in low-dropout conditions. The MIC2285A is available in the 10-pin 2mm x Applications 2mm Thin MLF package with a junction operating Cellular phones range from 40C to +125C. PDAs Data sheets and support documentation can be found on Micrels web site at: www.micrel.com. USB peripherals Typical Application 2.5V Efficiency OUT 100 90 V =3.2V IN 80 V =3.6V IN 70 V =4.2V IN 60 50 40 30 20 10 Adjustable Output Buck Regulator with LOWQ Mode 0 0 100 200 300 400 500 600 OUTPUT CURRENT (mA) LOWQ is a registered trademark of Micrel, Inc MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc. Micrel, Inc 2180 Fortune Drive San Jose, Ca 95131 USA tel +1 (408) 944-0800 fax +1 (408) 474-1000 Micrel, Inc. MIC2285A Ordering Information Output Junction Part Number Marking Package Lead Finish Voltage* Temperature Range MIC2285AYMT WPA Adj. 40 to +125C 10-Pin 2x2 Thin MLF Pb-free Note * For other voltage options available, please contact Micrel Marketing for details. MLF is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free. Pin Configuration AGND 1 10 PGND LDO 2 9 SW BIAS 3 8 VIN AVIN 4 7 LOWQ FB 5 6 EN 10-Pin 2mm x 2mm Thin MLF (MT) Pin Description Pin Number Pin Name Pin Function 1 AGND Analog (signal) Ground. 2 LDO LDO Output (Output): Connect to V for LDO mode operation. OUT 3 BIAS Internal circuit bias supply. Must be decoupled to signal ground with a 0.1F capacitor and should not be loaded. 4 AVIN Analog Supply Voltage (Input): Supply voltage for the analog control circuitry and LDO input power. Requires bypass capacitor to GND. 5 FB Feedback. Input to the error amplifier. For the Adjustable option, connect to the external resistor divider network to set the output voltage. For fixed output voltage options, connect to V and an internal resistor network sets the output OUT voltage. 6 EN Enable (Input). Logic low will shut down the device, reducing the quiescent current to less than 5A. Enable LDO Mode (Input): Logic low enables the internal LDO and disables the PWM operation. Logic high enables the PWM mode and disables the LDO 7 LOWQ mode. 8 VIN Supply Voltage (Input): Supply voltage for the internal switches and drivers. 9 SW Switch (Output): Internal power MOSFET output switches. 10 PGND Power Ground. M9999-083107-B August 2007 2