LTC3701 2-Phase, Low Input Voltage, Dual Step-Down DC/DC Controller FEATURES DESCRIPTIO n Out-of-Phase Controllers Reduce Required The LTC 3701 is a 2-phase dual constant frequency cur- Input Capacitance rent mode step-down DC/DC controller providing excellent n True PLL for Frequency Locking or Frequency load and line regulation. Power loss and noise due to ESR Adjustment of the input capacitor are minimized by operating the two n Operating Frequency Range: 300kHz to 750kHz controller output stages out-of-phase. n Wide V Range: 2.5V to 10V IN The LTC3701 provides a 0.8V 2% voltage reference and n Constant Frequency Current Mode Architecture consumes only 460m A of quiescent current. To further n Low Dropout: 100% Duty Cycle maximize the life of a battery source, the external n Power Good Output Voltage Monitor P-channel MOSFET is turned on continuously in dropout n Internal Soft-Start Circuitry (100% duty cycle). n Selectable Burst Mode /Pulse Skipping Operation Switching frequency is internally set at 550kHz, allowing at Light Loads n the use of small inductors and capacitors. For noise sen- Output Overvoltage Protection n sitive applications, the LTC3701 can be externally syn- Low Quiescent Current: 460m A n chronized using its phase-locked loop. The frequency can 0.8V 2% Voltage Reference n also be externally set from 300kHz to 750kHz by applying Small 16-Lead Narrow SSOP Package a voltage to the PLLLPF pin. Burst Mode operation is inhib- U ited during synchronization or when the EXTCLK/MODE APPLICATIO S pin is pulled low to reduce noise and RF interference. n One or Two Lithium-Ion Powered Applications The LTC3701 contains independent internal soft-start n Notebook and Handheld Computers circuitry for each controller. Other features include a n Personal Digital Assistants power good output voltage monitor and output overvolt- n Portable Instruments age and short-circuit protection. n Distributed DC Power Systems The LTC3701 is available in a small footprint 16-lead nar- , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. row SSOP package. TYPICAL APPLICATIO V IN 2.5V TO 9.8V Efficiency vs Load Current 100 169k V = 3.3V 1 16 V = 4.2V IN + IN SENSE1 SENSE1 V OUT1 L1 0.03 90 3 15 2.5V 220pF 78.7k V V 4.7H FB1 IN 10k 2A M1 + 2 14 I /RUN1 PGATE1 D1 TH 47F 10F 80 4 LTC3701 13 V = 6V SGND PGND IN 6 12 V = 8.4V IN I /RUN2 PGATE2 70 TH D2 10k 5 11 47F 80.6k V PGOOD 220pF FB2 7 10 M2 60 L2 V OUT2 PLLLPF EXTCLK/MODE 0.03 4.7H 1.8V 8 9 + 100k SENSE2 SENSE2 2A 50 V = 2.5V OUT 40 3701 F01a D1, D2: IR10BQ015 L1, L2: LQN6C-4R7 M1, M2: FDC638P 1 10 100 1000 10000 LOAD CURRENT (mA) 3701 F01b Figure 1. High Efficiency 2-Phase 550kHz Dual Step-Down Converter 3701fa 1 EFFICIENCY (%) + U ULTC3701 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW ORDER PART Input Supply Voltage (V )........................ 0.3V to 10V IN + NUMBER SENSE1 , SENSE2 , PGATE1, PGATE2, SENSE1 1 16 SENSE1 + + I /RUN1 2 15 V PLLLPF, SENSE1 , SENSE2 , TH IN LTC3701EGN V 3 14 PGATE1 FB1 EXTCLK/MODE Voltages .............. 0.3V to (V + 0.3V) IN SGND 4 13 PGND V , V , I /RUN1, FB1 FB2 TH V 5 12 PGATE2 FB2 I /RUN2 Voltages .................................. 0.3V to 2.4V TH I /RUN2 6 11 PGOOD TH GN PART PGOOD Voltage ........................................ 0.3V to 10V PLLLPF 7 10 EXTCLK/MODE MARKING PGATE1, PGATE2 Peak Output Current (<10m s)....... 1A + SENSE2 8 9 SENSE2 Operating Ambient Temperature Range 3701 GN PACKAGE (Note 2) ...................................................40 C to 85 C 16-LEAD PLASTIC SSOP Storage Ambient Temperature Range ... 65 C to 150 C T = 150 C, q = 140 C/W JMAX JA Junction Temperature (Note 3)............................ 125 C Consult LTC Marketing for parts specified with wider operating temperature ranges. Lead Temperature (Soldering, 10 sec).................. 300 C ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are T = 25 C. V = 4.2V unless otherwise noted. A IN PARAMETER CONDITIONS MIN TYP MAX UNITS Main Control Loops Input DC Supply Current (Note 4) Normal Operation 2.5V < V < 9.8V 460 780 m A IN Sleep Mode 2.5V < V < 9.8V 305 470 m A IN Shutdown 2.5V < V < 9.8V, I /RUN1 = I /RUN2 = 0V 9 28 m A IN TH TH UVLO V < UVLO Threshold 18 30 m A IN Undervoltage Lockout Threshold V Falling l 1.55 2.00 2.50 V IN V Rising 1.70 2.12 2.55 V IN Shutdown Threshold at I /RUN1, 2 0.2 0.35 0.5 V TH Start-Up Current Source on I /RUN1, 2 V /RUN1, 2 = 0V 0.25 0.5 0.85 m A TH ITH Regulated Feedback Voltage 0 C to 70 C (Note 5), I /RUN = 1.3V l 0.784 0.8 0.816 V TH 40 C to 85 C (Note 5) l 0.774 0.8 0.826 V Output Voltage Line Regulation 2.5V < V < 9.8V (Note 5) 0.05 0.20 mV/V IN Output Voltage Load Regulation I /RUN = 0.9V (Note 5) 0.2 0.8 % TH /RUN = 1.6V 0.2 0.8 % I TH V Input Current (Note 5) 10 50 nA FB1, 2 Output Overvoltage Protect Threshold Measured at V 0.835 0.88 0.930 V FB Output Overvoltage Protect Hysteresis 20 mV Gate Drive 1, 2 Rise Time C = 3000pF 40 ns L Gate Drive 1, 2 Fall Time C = 3000pF 40 ns L + Maximum Current Sense Voltage (SENSE SENSE ) (Note 6) 95 120 145 mV Soft-Start Current Sense Voltage Step 30 mV Time to Maximum Sense Voltage 2048 Cycles 3701fa 2 U WWW