LTC1771 10m A Quiescent Current High Efficiency Step-Down DC/DC Controller FEATURES DESCRIPTIO n Very Low Standby Current: 10m A The LTC 1771 is a high efficiency current mode step- n Available in Space-Saving 8-Lead MSOP Package down DC/DC controller that draws as little as 10m A DC n Output Currents: Up to 5A supply current to regulate the output at no load while n Wide V Range: 2.8V to 20V Operation maintaining high efficiency for loads up to several amps. IN n V Range: 1.23V to 18V OUT The LTC1771 drives an external P-channel power MOSFET n High Efficiency: Over 93% Possible using a current mode, constant off-time architecture. An n 2% Output Accuracy external sense resistor is used to program the operating n Very Low Dropout Operation: 100% Duty Cycle current level. Current mode control provides short-circuit n Current Mode Operation for Excellent Line and protection, excellent transient response and controlled Load Transient Response start-up behavior. Burst Mode operation enables the TM n Defeatable Burst Mode Operation LTC1771 to maintain high efficiency down to extremely n Short-Circuit Protected low currents. Shutdown mode further reduces the supply n Optional Programmable Soft-Start current to a mere 2m A. For low noise applications, Burst n Micropower Shutdown: I = 2m A Q Mode operation can be easily disabled with the MODE pin. U Wide input supply range of 2.8V to 18V (20V maximum) APPLICATIO S and 100% duty cycle operation for low dropout make the n LTC1771 ideal for a wide variety of battery-powered appli- Cellular Telephones and Wireless Modems n cations where maximizing battery life is important. 1- to 4-Cell Lithium-Ion-Powered Applications n Portable Instruments The LTC1771s availability in both 8-lead MSOP and SO n Battery-Powered Equipment packages provides for a minimum area solution. n Battery Chargers , LTC and LT are registered trademarks of Linear Technology Corporation. n Scanners Burst Mode is a trademark of Linear Technology Corporation. TYPICAL APPLICATIO V IN 4.5V TO 18V LTC1771 Efficiency + 100 R 22F SENSE 0.05 25V V = 5V IN 90 V = 10V IN M1 V IN SENSE Si6447DQ L1 RUN/SS PGATE 80 V = 15V IN 15H V C OUT SS LTC1771 I TH 3.3V 0.01F R 70 C 2A V V MODE UPS5817 + FB IN C OUT 10k GND 150F R2 C C 6.3V 60 1.64M 22OpF 1% 50 R1 V = 3.3V 1M OUT R = 0.05 SENSE 1% 40 C FF 1771 F01 0.1 1 10 100 1000 10000 5pF LOAD CURRENT (mA) 1771 F01b Figure 1. High Efficiency Step-Down Converter 1 EFFICIENCY (%) U ULTC1771 ABSOLUTE AXI U RATI GS (Note 1) Input Supply Voltage (V )........................ 0.3V to 20V Junction Temperature (Note 2)............................ 125 C IN Peak Driver Output Current < 10m s (PGATE) ............. 1A Operating Temperature Range (Note 3) RUN/SS Voltage ......................... 0.3V to (V + 0.3V)* LTC1771E......................................... 40 C to 85 C IN MODE Voltage .......................................... 0.3V to 20V LTC1771I ......................................... 40 C to 85 C I , V Voltage .......................................... 0.3V to 5V Storage Temperature Range ................. 65 C to 150 C TH FB SENSE Voltage (V > 12V)..(V 12V) to (V + 0.3V)* Lead Temperature (Soldering, 10 sec).................. 300 C IN IN IN SENSE Voltage (V 12V) ........ 0.3V to (V + 0.3V)* IN IN *RUN/SS and SENSE cannot exceed 20V. UUW PACKAGE/ORDER I FOR ATIO ORDER PART ORDER PART TOP VIEW NUMBER NUMBER TOP VIEW RUN/SS 1 8 MODE RUN/SS 1 8 MODE LTC1771EMS8 LTC1771ES8 I 2 7 SENSE TH I 2 7 SENSE TH LTC1771IS8 V 3 6 V IN FB V 3 6 V FB IN 5 PGATE GND 4 GND 4 5 PGATE MS8 PACKAGE S8 PART MARKING MS8 PART MARKING 8-LEAD PLASTIC MSOP S8 PACKAGE 8-LEAD PLASTIC SO T = 125 C, q = 200 C/ W JMAX JA LTKD 1771 T = 125 C, q = 110 C/ W JMAX JA 1771I Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are T = 25 C. A V = 10V, V = open unless otherwise specified. IN RUN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V Feedback Voltage (Note 5) l 1.205 1.230 1.255 V FB I Feedback Current (Note 5) l 110 nA FB I No-Load Supply Current V = 10V, I = 0 (Note 6) 10 m A SUPPLY IN LOAD D V Reference Voltage Line Regulation V = 5V to 15V (Note 5) l 0.003 0.03 %/V LINEREG IN D V Output Voltage Load Regulation I = 0.5V to 2V, Burst Disabled (Note 5) l 0.25 1 % LOADREG TH I Input DC Supply Current (Note 4) Q Active Mode (PGATE = 0V) V = 2.8V to 18V 150 235 m A IN Sleep Mode (Note 6) V = 2.8V to 18V, V = 1.5V 9 15 m A IN FB Shutdown V = 2.8V to 18V, V = 0V 2 6 m A IN RUN Short Circuit V = 2.8V to 18V, V = 0V 175 275 m A IN FB D V Maximum Current Sense Threshold V = V 20mV l 110 140 180 mV SENSE(MAX) FB REF D V Minimum Current Sense Threshold V = V + 20mV, Burst Disabled 25 mV SENSE(MIN) FB REF D V Sleep Current Sense Threshold I = 1V 50 mV SENSE(SLEEP) TH t Switch Off Time V at Regulated Value 3 3.5 4 m s OFF FB V = 0V 70 m s FB V Mode Pin Threshold V Rising l 0.5 1.3 2 V MODE MODE 2 U WWW