MIC2285 8MHz PWM Synchronous Buck Regulator with LDO Standby Mode General Description Features The Micrel MIC2285 is a high efficiency 8MHz pulse 2.7 to 5.5V supply/input voltage width modulated (PWM) synchronous buck (step- Light load LOWQ LDO mode down) regulator that features a LOWQ LDO standby 20A quiescent current mode that draws only 18A of quiescent current. The Low noise, 75Vrms MIC2285 allows an ultra-low noise, small size, and 8MHz PWM mode high efficiency solution for portable power applications. Output current to 500mA In PWM mode, the MIC2285 operates with a constant >90% efficiency frequency 8MHz PWM control. Under light load 100% maximum duty cycle conditions, such as in system sleep or standby modes, Adjustable output voltage option down to 1V the PWM switching operation can be disabled to reduce switching losses. In this light load LOWQ Fixed output voltage options available mode, the LDO maintains the output voltage and Ultra-fast transient response draws only 18A of quiescent current. The LDO mode Uses a tiny 0.47H inductor of operation saves battery life while not introducing Enables sub 1mm profile solution spurious noise and high ripple as experienced with Fully integrated MOSFET switches pulse skipping or bursting mode regulators. Micropower shutdown The MIC2285 operates from a 2.7V to 5.5V input Thermal shutdown and current limit protection voltage and features internal power MOSFETs that can Pb-free 10-pin 3mm x 3mm MLF package supply up to 500mA output current in PWM mode. It can operate with a maximum duty cycle of 100% for 40C to +125C junction temperature range use in low-dropout conditions. Applications The MIC2285 is available in the 10-pin 3mm x 3mm MLF package with a junction operating range from Cellular phones 40C to +125C. PDAs USB peripherals Data sheets and support documentation can be found on Micrels web site at: www.micrel.com. Typical Application 1.8V Efficiency OUT 100 V =3.2V IN 90 80 V =3.6V IN 70 V =4.2V IN 60 50 40 30 20 10 0 Adjustable Output Buck Regulator with LOWQ Mode 0 100 200 300 400 500 OUTPUT CURRENT (mA) Patent Pending LOWQ is a trademark of Micrel, Inc MLF and MicroLeadFrame are 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. MIC2285 Ordering Information Output Junction Part Number Package Lead Finish Voltage* Temperature Range MIC2285YML Adj. 40 to +125C 10-Pin 3x3 MLF Pb-free Note: * Other Voltage options available. Contact Micrel for details. Pin Configuration AGND 1 10 PGND LDO 2 9 SW BIAS 3 8 VIN AVIN 4 7 LOWQ FB 5 EP 6 EN 10-Pin 3mm x 3mm MLF (ML) 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 Internal circuit bias supply. Must be filtered from input voltage through an RC 3 BIAS 1 lowpass filter with a cutoff frequency . 2 ()20.5 (100nF) 4 AVIN Analog Supply/Input 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. Enable (Input). Logic low will shut down the device, reducing the quiescent 6 EN current to less than 5A. Enable LDO Mode (Input): Logic low enables the internal LDO and disables the 7 LOWQ PWM operation. Logic high enables the PWM mode and disables the LDO mode. 8 VIN Supply/Input Voltage (Input): Supply voltage for the internal switches and drivers. 9 SW Switch (Output): Internal power MOSFET output switches. 10 PGND Power Ground. EP GND Ground, backside pad. M9999-012406 January 2006 2 www.micrel.com