LTC1911-1.5/LTC1911-1.8 Low Noise, High Efficiency, Inductorless Step-Down DC/DC Converter FEATURES DESCRIPTIO n Low Noise Constant Frequency Operation The LTC 1911 is a switched capacitor step-down DC/DC n 2.7V to 5.5V Input Voltage Range converter that produces a 1.5V or 1.8V regulated output n No Inductors from a 2.7V to 5.5V input. The part uses switched capaci- n Typical Efficiency 25% Higher Than LDOs tor fractional conversion to achieve high efficiency over the n Shutdown Disconnects Load from V entire input range. No inductors are required. Internal cir- IN n Output Voltage: 1.8V 4% or 1.5V 4% cuitry controls the step-down conversion ratio to optimize n Output Current: 250mA efficiency as the input voltage and load conditions vary.* n Low Operating Current: I = 180m A Typ Typical efficiency is over 25% higher than that of a linear IN n Low Shutdown Current: I = 10m A Typ regulator. IN n Oscillator Frequency: 1.5MHz A unique constant frequency architecture provides a low n Soft-Start Limits Inrush Current at Turn On noise regulated output as well as lower input noise than n Short-Circuit and Overtemperature Protected conventional charge pump regulators. High frequency n Available in an 8-Pin MSOP Package operation (f = 1.5MHz) simplifies output filtering to OSC U further reduce conducted noise. To optimize efficiency, APPLICATIO S the part enters Burst Mode operation under light load conditions. n Handheld Computers n Cellular Phones Low operating current (180m A with no load, 10m A in n Smart Card Readers shutdown) and low external parts count (two 1m F flying n Portable Electronic Equipment capacitors and two 10m F bypass capacitors) make the n Handheld Medical Instruments LTC1911 ideally suited for space constrained battery- n Low Power DSP Supplies powered applications. The part is short-circuit and , LTC and LT are registered trademarks of Linear Technology Corporation. overtemperature protected, and is available in an 8-pin Burst Mode is a registered trademark of Linear Technology Corporation. MSOP package. *U.S. Patent 6,438,005 TYPICAL APPLICATIO Efficiency 90 Single Cell Li-Ion to 1.8V DC/DC Converter 80 100mA 250mA 70 LTC1911-1.8 2.7V TO 5.5V INPUT 1 8 V SS/SHDN IN 60 1-CELL Li-Ion V = 1.8V 2 6 OR + OUT 10F* C2 V OUT I = 250mA 3-CELL NiMH OUT 1F* 3 7 50 + 10F* C2 C1 IDEAL LDO 1F* 4 5 GND C1 40 1911 TA01 *CERAMIC CAPACITOR V = 1.8V OUT 30 2 34 5 6 INPUT VOLTAGE (V) 1911 G05 1911f 1 EFFICIENCY (%) U ULTC1911-1.5/LTC1911-1.8 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) ORDER PART V to GND ...................................................0.3V to 6V IN NUMBER SS/SHDN to GND........................ 0.3V to (V + 0.3V) TOP VIEW IN V 1 8 SS/SHDN V Short-Circuit Duration............................ Indefinite IN OUT + + LTC1911EMS8-1.5 C2 2 7 C1 Operating Temperature Range (Note 2) .. 40 C to 85 C C2 3 6 V OUT LTC1911EMS8-1.8 GND 4 5 C1 Storage Temperature Range ................. 40 C to 150 C MS8 PACKAGE MS8 PART MARKING Lead Temperature (Soldering, 10 sec).................. 300 C 8-LEAD PLASTIC MSOP T = 125 C, q = 160 C/ W JMAX JA LTMY LTNU Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are T = 25 C. V = 3.6V, C1 = 1m F, C2 = 1m F, C = 10m F, C = 10m F unless A IN IN OUT otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS V Operating Voltage l 2.7 5.5 V IN V LTC1911-1.5, 0mA I 250mA, V = 2.7V to 5.5V l 1.44 1.5 1.56 V OUT OUT IN LTC1911-1.8, 0mA I 250mA, V = 2.7V to 5.5V l 1.73 1.8 1.87 V OUT IN V Operating Current I = 0mA, V = 2.7V to 5.5V l 180 350 m A IN OUT IN V Shutdown Current SS/SHDN = 0V, V = 2.7V to 5.5V l 10 20 m A IN IN Output Ripple I = 10mA 5 mV OUT P-P I = 250mA 12 mV OUT P-P V Short-Circuit Current V = 0V 600 mA OUT OUT Switching Frequency Oscillator Free Running 1.2 1.5 1.8 MHz SS/SHDN Input Threshold l 0.3 0.6 1 V SS/SHDN Soft-Start Current V = 0V (Note 3) l 5 2 1 m A SS/SHDN V = V 0.01 m A SS/SHDN IN Turn-On Time C = 0pF, V = 3.3V 0.03 ms SS IN C = 10nF, V = 3.3V 10 ms SS IN Load Regulation 0V I 250mA 0.13 mV/mA OUT Line Regulation 0V I 250mA 0.3 %/V OUT Note 1: Absolute Maximum Ratings are those values beyond which the life Note 3: Currents flowing into the device are positive polarity. Currents of a device may be impaired. flowing out of the device are negative polarity. Note 2: The LTC1911E is guaranteed to meet specified performance from 0 C to 70 C. Specifications over the 40 C to 85 C operating temperature range are assured by design, characterization and correlation with statistical process controls. 1911f 2 U WWW