LTC3801/LTC3801B Micropower Constant Frequency Step-Down DC/DC Controllers in ThinSOT FEATURES DESCRIPTIO n High Efficiency: Up to 94% The LTC 3801/LTC3801B are constant frequency cur- n Very Low No-Load Quiescent Current: rent mode step-down DC/DC controllers in a low profile TM Only 16m A (LTC3801) (1mm max) 6-lead SOT-23 (ThinSOT ) package. The n High Output Currents Easily Achieved parts provide excellent AC and DC load and line regula- n Internal Soft-Start tion with 1.5% output voltage accuracy. The LTC3801 n Wide V Range: 2.4V to 9.8V consumes only 195m A of quiescent current in normal IN n Low Dropout: 100% Duty Cycle operation, dropping to 16m A under no-load conditions. n Constant Frequency 550kHz Operation The LTC3801/LTC3801B incorporate an undervoltage lock- n Burst Mode Operation for High Efficiency out feature that shuts down the device when the input at Light Loads (LTC3801) voltage falls below 2.2V. The LTC3801 automatically n Burst Mode Operation Disabled for Lower Output switches into Burst Mode operation at light loads which Ripple at Light Loads (LTC3801B) enhances efficiency at low output current. In the LTC3801B, n Output Voltage as Low as 0.8V Burst Mode operation is disabled for lower output ripple at n 1.5% Voltage Reference Accuracy light loads. n Current Mode Operation for Excellent Line and Load To further maximize the life of a battery source, the Transient Response n external P-channel MOSFET is turned on continuously in Only 6m A Supply Current in Shutdown (LTC3801) n dropout (100% duty cycle). High switching frequency of Low Profile (1mm) SOT-23 Package 550kHz allows the use of a small inductor. U APPLICATIO S , 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. n 1- or 2-Cell Li-Ion Battery-Powered Applications n Wireless Devices n Portable Computers n Distributed Power Systems LTC3801 Efficiency vs Load Current* TYPICAL APPLICATIO 100 V = 2.5V OUT V = 3.3V 95 IN V = 4.2V IN 550kHz Micropower Step-Down DC/DC Controller 90 85 220pF V = 6.6V IN V 10k IN 80 2.7V TO 9.8V I /RUN V TH IN 10F 75 LTC3801/ 0.025 V = 8.4V V = 9.8V IN LTC3801B IN 70 GND SENSE 65 V PGATE FB 402k 60 4.7H 55 V 866k OUT 2.5V 50 + 2A 0.1 1 10 100 1000 10000 47F LOAD CURRENT (mA) 3801 TA02 3801 TA01 *SEE NO-LOAD I vs INPUT VOLTAGE ON THE LAST PAGE OF THIS DATA SHEET Q sn3801 3801fs 1 EFFICIENCY (%) U ULTC3801/LTC3801B ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) ORDER PART Input Supply Voltage (V )........................ 0.3V to 10V IN TOP VIEW NUMBER SENSE , PGATE Voltages ............ 0.3V to (V + 0.3V) IN I /RUN 1 6 PGATE TH V , I /RUN Voltages ............................. 0.3V to 2.4V LTC3801ES6 FB TH GND 2 5 V IN PGATE Peak Output Current (<10m s) ........................ 1A LTC3801BES6 V 3 4 SENSE FB Operating Temperature Range (Note 2) .. 40 C to 85 C S6 PART MARKING S6 PACKAGE Junction Temperature (Note 3)............................ 150 C 6-LEAD PLASTIC TSOT-23 LTACR T = 150 C, q = 230 C/W Storage Temperature Range ................. 65 C to 150 C JMAX JA LTAHN Lead Temperature (Soldering, 10 sec).................. 300 C Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The l indicates specifications which apply over the full operating temperature range, otherwise specifications are at T = 25 C. V = 4.2V unless otherwise noted. (Note 2) A IN PARAMETER CONDITIONS MIN TYP MAX UNITS Input Voltage Range l 2.4 9.8 V Input DC Supply Current Typicals at V = 4.2V (Note 4) IN Normal Operation 2.4V V 9.8V, V /RUN = 1.3V 195 300 m A IN ITH SLEEP Mode 2.4V V 9.8V (LTC3801 Only) 16 30 m A IN Shutdown 2.4V V 9.8V, V /RUN = 0V (LTC3801) 6 15 m A IN ITH 2.4V V 9.8V, V /RUN = 0V (LTC3801B) 8 17 m A IN ITH UVLO V < UVLO Threshold 1 2 m A IN Undervoltage Lockout Threshold V Rising l 1.8 2.3 V IN V Falling l 1.7 2.2 V IN Start-Up Current Source V /RUN = 0V (LTC3801) 0.5 1 1.5 m A ITH V /RUN = 0V (LTC3801B) 1.0 2 3.0 m A ITH Shutdown Threshold (at I /RUN) V /RUN Rising l 0.3 0.6 0.95 V TH ITH Regulated Feedback Voltage 0 C T 85 C (Note 5) 0.788 0.800 0.812 V A 40 C T 85 C (Note 5) l 0.780 0.800 0.812 V A Feedback Voltage Line Regulation 2.4V V 9.8V (Note 5) 0.05 mV/V IN Feedback Voltage Load Regulation I /RUN Sinking 5m A (Note 5) 2 mV/m A TH I /RUN Sourcing 5m A (Note 5) 2 mV/m A TH V Input Current (Note 5) 2 10 nA FB Overvoltage Protect Threshold Measured at V 0.850 0.880 0.910 V FB Overvoltage Protect Hysteresis 40 mV Oscillator Frequency Normal Operation V = 0.8V 500 550 650 kHz FB Output Short Circuit V = 0V 210 kHz FB Gate Drive Rise Time C = 3000pF 40 ns LOAD Gate Drive Fall Time C = 3000pF 40 ns LOAD Peak Current Sense Voltage Duty Cycle < 40% (Note 6) LTC3801 l 109 117 125 mV LTC3801B l 95 104 113 mV Peak Current Sense Voltage in Burst Mode Operation LTC3801 Only 26 mV Default Soft-Start Time 0.6 ms T = T + (P q C/W) Note 1: Absolute Maximum Ratings are those values beyond which the life J A D JA of a device may be impaired. Note 4: Dynamic supply current is higher due to the gate charge being Note 2: The LTC3801ES6/LTC3801BES6 are guaranteed to meet specifica- delivered at the switching frequency. tions from 0 C to 70 C. Specifications over the 40 C to 85 C operating Note 5: The LTC3801/LTC3801B are tested in a feedback loop that servos temperature range are assured by design, characterization and correlation V to the output of the error amplifier while maintaining I /RUN at the FB TH with statistical process controls. midpoint of the current limit range. Note 3: T is calculated from the ambient temperature T and power J A Note 6: Peak current sense voltage is reduced dependent on duty cycle as dissipation P according to the following formula: D given in Figure 1. sn3801 3801fs 2 U W U U WWW