LTC1878 High Efficiency Monolithic Synchronous Step-Down Regulator FEATURES DESCRIPTIO n High Efficiency: Up to 95% The LTC 1878 is a high efficiency monolithic synchro- n Very Low Quiescent Current: Only 10m A nous buck regulator using a constant frequency, current During Operation mode architecture. Supply current during operation is n 600mA Output Current at V = 3.3V only 10m A and drops to < 1m A in shutdown. The 2.65V to IN n 2.65V to 6V Input Voltage Range 6V input voltage range makes the LTC1878 ideally suited n 550kHz Constant Frequency Operation for single Li-Ion battery-powered applications. 100% duty n Synchronizable from 400kHz to 700kHz cycle provides low dropout operation, extending battery TM n Selectable Burst Mode Operation or life in portable systems. Pulse Skipping Mode Switching frequency is internally set at 550kHz, allowing n No Schottky Diode Required the use of small surface mount inductors and capacitors. n Low Dropout Operation: 100% Duty Cycle For noise sensitive applications the LTC1878 can be n 0.8V Reference Allows Low Output Voltages externally synchronized from 400kHz to 700kHz. Burst n Shutdown Mode Draws < 1m A Supply Current Mode operation is inhibited during synchronization or n 2% Output Voltage Accuracy when the SYNC/MODE pin is pulled low, preventing low n Current Mode Control for Excellent Line and frequency ripple from interfering with audio circuitry. Load Transient Response n Overcurrent and Overtemperature Protected The internal synchronous switch increases efficiency and n Available in 8-Lead MSOP Package eliminates the need for an external Schottky diode. Low U output voltages are easily supported with the 0.8V feed- APPLICATIO S back reference voltage. The LTC1878 is available in a n Cellular Telephones space saving 8-lead MSOP package. n Wireless Modems For higher input voltage (11V abs max) applications, refer n Personal Information Appliances to the LTC1877 data sheet. n Portable Instruments , LTC and LT are registered trademarks of Linear Technology Corporation. n Distributed Power Systems Burst Mode is a trademark of Linear Technology Corporation. n Battery-Powered Equipment Efficiency vs Output Load Current TYPICAL APPLICATIO 100 V = 3.6V 95 IN High Efficiency Step-Down Converter 10H* 90 V IN 7 5 V OUT SW V = 4.2V 2.65V SYNC IN 3.3V 20pF TO 6V 6 22F** V 85 IN + CER LTC1878 1 47F*** V = 6V RUN IN 887k 80 2 3 I V TH FB GND 280k 220pF 4 75 Burst Mode OPERATION V = 3.3V OUT 1878 TA01 L = 10H 70 *TOKO D62CB A920CY-100M 0.1 1 10 100 1000 **TAIYO-YUDEN CERAMIC JMK325BJ226MM OUTPUT CURRENT (mA) ***SANYO POSCAP 6TPA47M V CONNECTED TO V FOR 2.65V < V < 3.3V 1878 TA02 OUT IN IN 1 EFFICIENCY (%) U ULTC1878 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) Input Supply Voltage (V )...........................0.3V to 7V IN ORDER PART I , PLL LPF Voltage ................................0.3V to 2.7V NUMBER TH TOP VIEW RUN, V Voltages ...................................... 0.3V to V RUN PLL LPF 1 8 FB IN I 2 7 SYNC/MODE TH SYNC/MODE Voltage .................................. 0.3V to V LTC1878EMS8 IN V 6 V 3 FB IN GND 4 5 SW SW Voltage ................................... 0.3V to (V + 0.3V) IN MS8 PACKAGE P-Channel MOSFET Source Current (DC) ........... 800mA MS8 PART MARKING 8-LEAD PLASTIC MSOP N-Channel MOSFET Sink Current (DC) ............... 800mA T = 125 C, q = 150 C/ W JMAX JA Peak SW Sink and Source Current ........................ 1.5A LTNX Operating Ambient Temperature Range Consult factory for Industrial and Military grade parts. (Note 2) .................................................. 40 C to 85 C Junction Temperature (Note 3)............................ 125 C Storage Temperature Range ................. 65 C to 150 C Lead Temperature (Soldering, 10 sec).................. 300 C ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are T = 25 C. A V = 3.6V unless otherwise specified. IN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS I Feedback Current (Note 4) l 430 nA VFB V Regulated Output Voltage (Note 4) 0 C T 85 C 0.784 0.8 0.816 V FB A (Note 4) 40 C T 85 C l 0.74 0.8 0.84 V A D V Output Overvoltage Lockout D V = V V l 20 50 110 mV OVL OVL OVL FB D V Reference Voltage Line Regulation V = 2.65V to 6V (Note 4) 0.05 0.2 %/V FB IN V Output Voltage Load Regulation Measured in Servo Loop V = 0.9V to 1.2V l 0.1 0.5 % LOADREG ITH Measured in Servo Loop V = 1.6V to 1.2V l 0.1 0.5 % ITH V Input Voltage Range l 2.65 6 V IN I Input DC Bias Current (Note 5) Q Pulse Skipping Mode 2.65V < V < 6V, V = 0V, I = 0A 230 350 m A IN SYNC/MODE OUT Burst Mode Operation V = V , I = 0A 10 15 m A SYNC/MODE IN OUT Shutdown V = 0V, V = 6V 0 1 m A RUN IN f Oscillator Frequency V = 0.8V 495 550 605 kHz OSC FB V = 0V 80 kHz FB f SYNC Capture Range 400 700 kHz SYNC I Phase Detector Output Current PLL LPF Sinking Capability f < f l 3 10 20 m A PLLIN OSC Sourcing Capability f > f l 3 10 20 m A PLLIN OSC R R of P-Channel MOSFET I = 100mA 0.5 0.7 W PFET DS(ON) SW R R of N-Channel MOSFET I = 100mA 0.6 0.8 W NFET DS(ON) SW 2 U WWW