POWER LOSS (mW) LTC3447 2 I C Controllable Buck Regulator in 3mm 3mm DFN FEATURES DESCRIPTIO 2 I C Programmable Output with 21.6mV Resolution The LTC 3447 is a high ef ciency monolithic synchronous 2 Overtemperature Protected current mode buck regulator. Using an I C interface, the High Ef ciency: Up to 93% output voltage can be set between 0.69V and 2.05V using Very Low Quiescent Current: Only 33A an internal 6-bit DAC. 600mA Output Current at V = 3V IN The buck regulator has optional external feedback resis- 2.5V to 5.5V Input Voltage Range tors that can be used for setting the initial start up voltage. 1MHz Constant Frequency Operation The feedback voltage reference for this start-up option No Schottky Diode Required 2 is 0.6V. Once the voltage DAC is updated via the I C, the Low Dropout Operation: 100% Duty Cycle buck regulator switches from external to internal feedback Stable with Ceramic Capacitors resistors. When there are no external resistors, the default Shutdown Mode Draws <1A Supply Current start-up voltage is 1.38V. 2% Output Voltage Accuracy 2 The switching frequency is internally set at 1MHz, al- Standard (100kHz) or Fast Mode (400kHz) I C lowing the use of small surface mount inductors and 6-Bit Voltage DAC (0.69V to 2.05V) capacitors. Disable Burst Mode Operation Enable Power Good Blanking In Burst Mode operation, supply current is only 33A, Optional External Start-Up Resistors dropping to <1A in shutdown. The 2.5V to 5.5V input Soft-Start voltage range makes the LTC3447 ideally suited for single 10 Lead, 3mm 3mm DFN Package cell Li-Ion battery-powered applications. 100% duty cycle U capability provides low dropout operation, extending APPLICATIO S battery life in portable systems. Automatic Burst Mode Distributed Power Supplies operation increases ef ciency at light loads, further ex- Notebook Computers tending battery life. PDAs and Other Handheld Devices The internal synchronous switch increases ef ciency and , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. eliminates the need for an external Schottky diode. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131. Ef ciency and Power Loss vs TYPICAL APPLICATIO Load Current (V = 3.6V) IN V IN 1000 100 2.5V TO 5.5V C2 4.7F V IN 90 CERAMIC 80 RPU1 20k 70 V IN 100 2 PWREN RUN PGOOD I C V CCD V 60 OUT LTC3447 0.69V 50 V SW CCD TO 2.05V L1 C3 C1 AT 600mA* 3.3H 40 10k 10k 4.7F 10F R1 SDA V OUT 10 100k 30 SDA SCL FB 20 SCL PULSE SKIP EFFICIENCY R2 Burst Mode EFFICIENCY 10 GND 49.9k LOSS * 600mA AT V = 3V IN 0 1 EXPOSED PADDLE 1 10 100 1000 TO GROUND 3447 TA01 3447 TA01b LOAD CURRENT (mA) 3447f 1 EFFICIENCY (%) U ULTC3447 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) ORDER PART TOP VIEW V , V Voltages .......................................0.3V to 6V IN CCD NUMBER RUN, V , FB Voltages .............................. 0.3V to V OUT IN V 1 10 SDA OUT SW Voltage ................................... 0.3V to (V + 0.3V) LTC3447EDD GND 2 9 V IN CCD FB 3 11 8 SCL SCL, SDA Voltages ................................... 0.3V to V CCD PGOOD 4 7 RUN P-Channel Switch Source Current (DC) ...............800mA V 5 6 SW IN DD PART N-Channel Switch Sink Current (DC) ...................800mA MARKING Peak SW Sink and Source Current ...........................1.3A DD PACKAGE 10-LEAD (3mm x 3mm)PLASTIC DFN Operating Temperature Range (Note 2) ...40C to 85C EXPOSED PAD IS GND (PIN 11) LBKB MUST BE SOLDERED TO PCB Junction Temperature (Note 3) ............................. 125C T = 125C, = 43C/W, = 2.96C/W JMAX JA JC Storage Temperature Range ...................65C to 125C Consult LTC Marketing for parts speci ed with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes the speci cations which apply over the full operating temperature range, otherwise speci cations are at T = 25C. V = 3.6V unless otherwise speci ed. A IN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS RUN Run Threshold 0.3 1 1.5 V PGOOD Reports Undervoltage PGOOD = 0.4V 3 mA R Feedback Resistance 460 k VOUT V Regulated Output Voltage 0.669 0.69 0.711 V OUT(MIN) V Regulated Output Voltage 1.989 2.05 2.112 V OUT(MAX) V Output Voltage Step Size (6-bits) 20.3 21.6 22.9 mV OUT V Output Voltage Line Regulation V = 2.5V to 5.5V (Note 6) 0.2 1.2 %/V OUT IN 0.2 1 %/V I Peak Inductor Current Duty Cycle < 35%, Wafer Level 0.75 1 1.25 A PK V Output Voltage Load Regulation 0.5 % LOADREG V Input Voltage Range 2.5 5.5 V IN I Input DC Bias Current (Note 4) S Burst Mode Operation I = 0A 34 60 A LOAD Active Mode V = 90%, I = 0A 280 400 A OUT LOAD Shutdown V = 0V, V = 5.5V 0.1 1 A RUN IN f Nominal Oscillator Frequency V = 100% 0.7 1 1.3 MHz OSC OUT V = 0V 160 kHz OUT R R of P-Channel FET I = 100mA, Wafer Level 0.32 PFET DS(ON) SW R R of N-Channel FET I = 100mA, Wafer Level 0.22 NFET DS(ON) SW I SW Leakage V = 0V, V = 0V or 5V, V = 5V 0.1 1 A LSW RUN SW IN FB Optional Start-Up Feedback Voltage Regulated Feedback Voltage 0.6 V I Feedback Input Current 2.5 10 nA FB 2 SCL I C Clock Logic Threshold (Note 5) V V THR CCD/2 2 SCL I C Clock Logic Hysteresis (Note 5) 300 mV HYST 2 SDA I C Data Logic Threshold (Note 5) V V THR CCD/2 2 SDA I C Data Logic Hysteresis (Note 5) 300 mV HYST 3447f 2 U WWW