LTC3736-1 TM Dual 2-Phase, No R , SENSE Synchronous Controller with Spread Spectrum FEATURES DESCRIPTIO Spread Spectrum Operation The LTC 3736-1 is a 2-phase dual synchronous step- Tracking Function down switching regulator controller with tracking that No Current Sense Resistors Required drives external complementary power MOSFETs using Out-of-Phase Controllers Reduce Required few external components. The constant frequency current Input Capacitance mode architecture with MOSFET V sensing eliminates DS Wide V Range: 2.75V to 9.8V the need for sense resistors and improves efficiency. IN Current Mode Operation Power loss and noise due to the ESR of the input capaci- 0.6V 1.5% Voltage Reference tance are minimized by operating the two controllers out Low Dropout Operation: 100% Duty Cycle of phase. Pulse Skipping Operation at Light Loads A unique spread spectrum architecture randomly varies Internal Soft-Start Circuitry the LTC3736-1s switching frequency from 450kHz to Power Good Output Voltage Monitor 580kHz, significantly reducing the peak radiated and con- Output Overvoltage Protection ducted noise on both the input and output supplies, Micropower Shutdown: I = 9A Q making it easier to comply with electromagnetic interfer- Tiny Low Profile (4mm 4mm) QFN and Narrow ence (EMI) standards. SSOP Packages Pulse skipping operation provides high efficiency at light U loads. 100% duty cycle capability provides low dropout op- APPLICATIO S eration, extending operating time in battery-powered sys- tems. The high switching frequencies allow for the use of One or Two Lithium-Ion Powered Devices small surface mount inductors and capacitors. Notebook and Palmtop Computers, PDAs Portable Instruments The LTC3736-1 is available in the low profile (0.75mm) Distributed DC Power Systems 24-pin thermally enhanced (4mm 4mm) QFN package , LTC and LT are registered trademarks of Linear Technology Corporation. and 24-lead narrow SSOP packages. No R is a trademark of Linear Technology Corporation. SENSE Protected by U.S. Patents including 5481178, 5929620, 6144194, 6580258, 6304066, 6611131, 6498466. TYPICAL APPLICATIO Output Voltage Frequency Low Noise, 2-Phase, Dual Synchronous DC/DC Step-Down Converter Spectrum V 10 IN FIGURE 13 CIRCUIT 2.75V TO 9.8V SPREAD SPECTRUM 20 V = 2.5V 10F OUT DISABLED V IN R = 30Hz 2 BW + + 30 SENSE1 SENSE2 SPREAD SPECTRUM 40 ENABLED TG1 TG2 50 2.2H 2.2H SW1 SW2 60 LTC3736-1 BG1 BG2 70 PGND PGND 80 187k 118k V V OUT1 OUT2 V V 90 FB1 FB2 2.5V 1.8V I I 100 TH1 TH2 + + 220pF 220pF SGND 47F 47F 110 410k 450k 490k 530k 570k 610k 59k 15k 59k 15k FREQUENCY (Hz) 37361 TA01b 37361 TA01a 37361f 1 AMPLITUDE (dBm) U ULTC3736-1 ABSOLUTE AXI U RATI GS (Note 1) Input Supply Voltage (V ) ........................ 0.3V to 10V TG1, TG2, BG1, BG2 Peak Output Current (<10s) ..... 1A IN FREQ, RUN/SS, SSDIS, Operating Temperature Range (Note 2) ... 40C to 85C + + TRACK, SENSE1 , SENSE2 , Storage Temperature Range .................. 65C to 125C IPRG1, IPRG2 Voltages ................. 0.3V to (V + 0.3V) Junction Temperature (Note 3) ............................ 125C IN V , V , I , I Voltages .................. 0.3V to 2.4V Lead Temperature (Soldering, 10 sec) FB1 FB2 TH1 TH2 SW1, SW2 Voltages ............ 2V to V + 1V or 10V Max (LTC3736EGN-1) .................................................. 300C IN PGOOD ..................................................... 0.3V to 10V UUW PACKAGE/ORDER I FOR ATIO TOP VIEW ORDER PART ORDER PART TOP VIEW NUMBER NUMBER + SW1 1 24 SENSE1 IPRG1 2 23 PGND LTC3736EUF-1 LTC3736EGN-1 24 23 22 21 20 19 V 3 22 BG1 FB1 I 1 18 SSDIS TH1 I 4 21 SSDIS TH1 IPRG2 2 17 TG1 IPRG2 5 20 TG1 FREQ 3 16 PGND 25 FREQ 6 19 PGND SGND 4 15 TG2 SGND 7 18 TG2 V 5 14 RUN/SS IN V 8 17 RUN/SS IN TRACK 6 13 BG2 UF PART MARKING TRACK 9 16 BG2 7 8 9 10 11 12 V 10 15 PGND FB2 3736-1 + I 11 14 SENSE2 TH2 PGOOD 12 13 SW2 UF PACKAGE 24-LEAD (4mm 4mm) PLASTIC QFN GN PACKAGE 24-LEAD PLASTIC SSOP T = 125C, = 37C/W JMAX JA EXPOSED PAD (PIN 25) IS PGND T = 125C, = 130C/ W JMAX JA MUST BE SOLDERED TO PCB Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes specifications that apply over the full operating temperature range, otherwise specifications are at T = 25C. V = 4.2V unless otherwise specified. A IN PARAMETER CONDITIONS MIN TYP MAX UNITS Main Control Loops Input DC Supply Current (Note 4) Normal Mode 500 850 A Shutdown RUN/SS = 0V 9 20 A UVLO V < UVLO Threshold 3 10 A IN Undervoltage Lockout Threshold V Falling 1.95 2.25 2.55 V IN V Rising 2.15 2.45 2.75 V IN Shutdown Threshold at RUN/SS 0.45 0.65 0.85 V Start-Up Current Source RUN/SS = 0V 0.5 0.7 1 A Regulated Feedback Voltage 0C to 85C (Note 5) 0.591 0.6 0.609 V 40C to 85C 0.588 0.6 0.612 V Output Voltage Line Regulation 2.75V < V < 9.8V (Note 5) 0.05 0.2 mV/V IN 37361f 2 V V FB2 FB1 I IPRG1 TH2 PGOOD SW1 + SW2 SENSE1 + SENSE2 PGND PGND BG1 U WWW