MIC2245 4MHz PWM Synchronous Buck Regulator with LDO Standby Mode General Description Features The Micrel MIC2245 is a high efficiency 4MHz 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 20A quiescent current standby mode that draws only 18A of quiescent Low noise, 75Vrms current. The MIC2245 allows an ultra-low noise, 4MHz PWM mode small size, and high efficiency solution for portable power applications. Output current to 500mA >92% efficiency In PWM mode, the MIC2245 operates with a constant frequency 4MHz PWM control. Under light 100% maximum duty cycle load conditions, such as in system sleep or standby Adjustable output voltage option down to 1V modes, the PWM switching operation can be Fixed output voltage options available disabled to reduce switching losses. In this light Ultra-fast transient response load LOWQ mode, the LDO maintains the output voltage and draws only 18A of quiescent current. Uses a tiny 1H inductor The LDO mode of operation saves battery life while Fully integrated MOSFET switches not introducing spurious noise and high ripple as Micropower shutdown operation experienced with pulse skipping or bursting mode Thermal shutdown and current limit protection regulators. Pb-free 10-pin 3mm x 3mm MLF package The MIC2245 operates from a 2.7V to 5.5V input 40C to +125C junction temperature range voltage and features internal power MOSFETs that can supply up to 500mA output current in PWM mode. It can operate with a maximum duty cycle of Applications 100% for use in low-dropout conditions. Cellular phones The MIC2245 is available in the 10-pin 3mm x 3mm MLF package with a junction operating range from PDAs 40C to +125C. USB peripherals Data sheet and support documentation can be found on Micrels web site at: www.micrel.com. Typical Application 1.8V Efficiency OUT 100 90 80 V =3.2V IN 70 V =3.6V IN V =4.2V IN 60 50 40 30 20 10 0 0 100 200 300 400 500 Adjustable Output Buck Regulator with LOWQ Mode 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. MIC2245 Ordering Information Output Junction Part Number Package Lead Finish Voltage* Temperature Range MIC2245YML 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 3 BIAS Internal circuit bias supply. Must be filtered from input voltage through an RC 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. 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 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