LTC3801_1

LTC3801/LTC3801B Micropower Constant Frequency Step-Down DC/DC Controllers in ThinSOT FEATURES s s DESCRIPTIO s s s s s s s s s s s s High Efficiency: Up to 94% Very Low No-Load Quiescent Current: Only 16µA (LTC3801) High Output Currents Easily Achieved Internal Soft-Start Wide VIN Range: 2.4V to 9.8V Low Dropout: 100% Duty Cycle Constant Frequency 550kHz Operation Burst Mode® Operation for High Efficiency at Light Loads (LTC3801) Burst Mode Operation Disabled for Lower Output Ripple at Light Loads (LTC3801B) Output Voltage as Low as 0.8V ±1.5% Voltage Reference Accuracy Current Mode Operation for Excellent Line and Load Transient Response Only 6µA Supply Current in Shutdown (LTC3801) Low Profile (1mm) SOT-23 Package The LTC®3801/LTC3801B are constant frequency current mode step-down DC/DC controllers in a low profile (1mm max) 6-lead SOT-23 (ThinSOTTM) package. The parts provide excellent AC and DC load and line regulation with ±1.5% output voltage accuracy. The LTC3801 consumes only 195µA of quiescent current in normal operation, dropping to 16µA under no-load conditions. The LTC3801/LTC3801B incorporate an undervoltage lockout feature that shuts down the device when the input voltage falls below 2.2V. The LTC3801 automatically switches into Burst Mode operation at light loads which enhances efficiency at low output current. In the LTC3801B, Burst Mode operation is disabled for lower output ripple at light loads. To further maximize the life of a battery source, the external P-channel MOSFET is turned on continuously in dropout (100% duty cycle). High switching frequency of 550kHz allows the use of a small inductor. , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. APPLICATIO S s s s s 1- or 2-Cell Li-Ion Battery-Powered Applications Wireless Devices Portable Computers Distributed Power Systems TYPICAL APPLICATIO LTC3801 Efficiency vs Load Current* 100 95 VOUT = 2.5V VIN = 4.2V VIN = 3.3V 550kHz Micropower Step-Down DC/DC Controller 10k VIN ITH/RUN LTC3801/ LTC3801B GND SENSE – VFB 402k 866k 4.7µH VOUT 2.5V 2A PGATE 0.025Ω 10µF VIN 2.7V TO 9.8V EFFICIENCY (%) 90 85 80 75 70 65 60 55 50 0.1 1 10 100 1000 LOAD CURRENT (mA) 10000 VIN = 9.8V VIN = 8.4V VIN = 6.6V 220pF + 47µF 3801 TA01 *SEE NO-LOAD IQ vs INPUT VOLTAGE ON THE LAST PAGE OF THIS DATA SHEET sn3801 3801fs U 3801 TA02 U U 1 LTC3801/LTC3801B ABSOLUTE MAXIMUM RATINGS (Note 1) PACKAGE/ORDER INFORMATION TOP VIEW ITH/RUN 1 GND 2 VFB 3 6 PGATE 5 VIN 4 SENSE – Input Supply Voltage (VIN)........................ – 0.3V to 10V SENSE –, PGATE Voltages ............ – 0.3V to (VIN + 0.3V) VFB, ITH/RUN Voltages ............................. – 0.3V to 2.4V PGATE Peak Output Current (