LTC1265/LTC1265-3.3/LTC1265-5 1.2A, High Efficiency Step-Down DC/DC Converter FEATURES DESCRIPTIO n High Efficiency: Up to 95% The LTC 1265 is a monolithic step-down current mode TM n DC/DC converter featuring Burst Mode operation at low Current Mode Operation for Excellent Line and Load output current. The LTC1265 incorporates a 0.3W switch Transient Response n Internal 0.3W Power Switch (V = 10V) (V =10V) allowing up to 1.2A of output current. IN IN n Short-Circuit Protection Under no load condition, the converter draws only 160m A. n Low Dropout Operation: 100% Duty Cycle In shutdown it typically draws a mere 5m A making this n Low-Battery Detector converter ideal for current sensitive applications. In drop- n Low 160m A Standby Current at Light Loads out the internal P-channel MOSFET switch is turned on n Active-High Micropower Shutdown: I < 15m A Q continuously maximizing the life of the battery source. The n Peak Inductor Current Independent of Inductor Value LTC1265 incorporates automatic power saving Burst Mode n Available in 14-pin SO Package operation to reduce gate charge losses when the load U currents drop below the level required for continuous APPLICATIO S operation. n 5V to 3.3V Conversion The inductor current is user-programmable via an external n Distributed Power Systems current sense resistor. Operation up to 700kHz permits n Step-Down Converters the use of small surface mount inductors and capacitors. n Inverting Converters , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a trademark of Linear Technology Corporation. n Memory Backup Supply n Portable Instruments n Battery-Powered Equipment n Cellular Telephones TYPICAL APPLICATIO V IN 5.4V TO LTC1265-5 Efficiency 12V + C IN 100 68m F 0.1m F L1* R ** V PWR V SENSE IN IN 20V 33m H V 0.1W OUT V = 6V IN SW SHDN 5V 95 1A V = 9V IN LTC1265-5 D1 1k + C OUT 90 I TH 220m F PGND V = 12V IN 10V 3900pF 85 + C T SENSE 130pF 1000pF 80 L = 33m H SENSE V = 5V OUT 75 R = 0.1W * COILTRONICS CTX33-4 SENSE SGND C = 130pF ** IRC LRC2010-01-R100-J T MBRS130LT3 70 AVX TPSE227K010 0.01 0.10 1.00 AVX TPSE686K020 LOAD CURRENT (A) LTC1265-FO1 LTC1265 TA01 Figure 1. High Efficiency Step-Down Converter 1 EFFICIENCY (%) U ULTC1265/LTC1265-3.3/LTC1265-5 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Voltages Refer to GND Pin) (Note 1) TOP VIEW ORDER PART Input Supply Voltage (Pins 1, 2, 13) ..........0.3V to 13V NUMBER PWR V 1 14 SW IN DC Switch Current (Pin 14) .................................... 1.2A V 2 13 PWR V IN IN Peak Switch Current (Pin 14) ................................. 1.6A LTC1265CS LB 3 12 PGND OUT Switch Voltage (Pin 14) .................................. V 13.0 LTC1265CS-5 IN LB 4 11 SGND IN Operating Temperature Range LTC1265CS-3.3 C 5 10 SHDN T LTC1265C ............................................... 0 to 70 C LTC1265IS I 6 9 N/C (V *) TH FB LTC1265I ........................................ 40 C to 85 C + SENSE 7 8 SENSE Junction Temperature (Note 2)............................. 125 C S PACKAGE Storage Temperature Range ....................65 to 150 C 14-LEAD PLASTIC SO Lead Temperature (Soldering, 10 sec).................. 300 C *ADJUSTABLE OUTPUT VERSION T = 125C, q = 110C/W JMAX JA Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25 C. V = 10V, V = 0V, unless otherwise specified. A IN SHDN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS I Feedback Current into Pin 9 LTC1265 0.2 1 m A FB V Feedback Voltage LTC1265C l 1.22 1.25 1.28 V FB = 9V, LTC1265I l 1.20 1.25 1.30 V V IN V Regulator Output Voltage LTC1265-3.3: I = 800mA l 3.22 3.3 3.40 V OUT LOAD LTC1265-5: I = 800mA l 4.9 5 5.2 V LOAD D V Output Voltage Line Regulation V = 6.5V to 10V, I = 800mA 40 0 40 mV OUT IN LOAD Output Voltage Load Regulation LTC1265-3.3: 10mA < I < 800mA 40 65 mV LOAD < 800mA 60 100 mV LTC1265-5: 10mA < I LOAD Burst Mode Operation Output Ripple I = 0mA 50 mV LOAD P-P I Input DC Supply Current (Note 3) Active Mode: 3.5V < V < 10V 1.8 2.4 mA Q IN Sleep Mode: 3.5V < V < 10V 160 230 m A IN Sleep Mode: 5V < V < 10V (LTC1265-5) 160 230 m A IN Shutdown: V = V , 3.5V < V < 10V 5 15 m A SHDN IN IN V Low-Battery Trip Point 1.15 1.25 1.35 V LBTRIP I Current into Pin 4 0.5 m A LBIN I Current Sunk by Pin 3 V = 0.4V, V = 0V 0.5 1.0 1.5 mA LBOUT LBOUT LBIN V = 5V, V = 10V 1.0 m A LBOUT LBIN V V Current Sense Threshold Voltage LTC1265: V = 5V, V = V /4 + 25mV (Forced) 25 mV 8 7 SENSE 9 OUT V = 5V, V = V /4 25mV (Forced) 130 150 180 mV SENSE 9 OUT LTC1265-3.3: V = V + 100mV (Forced) 25 mV SENSE OUT V = V 100mV (Forced) 130 150 180 mV SENSE OUT LTC1265-5: V = V + 100mV (Forced) 25 mV SENSE OUT V = V 100mV (Forced) 130 150 180 mV SENSE OUT R ON Resistance of Switch LTC1265C l 0.3 0.60 W ON LTC1265I 0.3 0.70 W I C Pin Discharge Current V in Regulation, V = V 40 60 100 m A 5 T OUT SENSE OUT V = 0V 2 10 m A OUT t Switch Off Time (Note 4) C = 390pF, I = 800mA (LTC1265C) l 456 m s OFF T LOAD C = 390pF, I = 800mA (LTC1265I) l 3.5 5 7 m s T LOAD 2 U WWW