LTC1628/LTC1628-PG High Efficiency, 2-Phase Synchronous Step-Down Switching Regulators FEATURES DESCRIPTIO n Out-of-Phase Controllers Reduce Required Input The LTC 1628/LTC1628-PG are high performance dual Capacitance and Power Supply Induced Noise step-down switching regulator controllers that drive all n OPTI-LOOP Compensation Minimizes C N-channel synchronous power MOSFET stages. A con- OUT n 1% Output Voltage Accuracy stant frequency current mode architecture allows adjust- n Dual N-Channel MOSFET Synchronous Drive ment of the frequency up to 300kHz. Power loss and noise n Power Good Output Voltage Monitor (LTC1628-PG) due to the ESR of the input capacitors are minimized by n DC Programmed Fixed Frequency 150kHz to 300kHz operating the two controller output stages out of phase. n Wide V Range: 3.5V to 36V Operation IN OPTI-LOOP compensation allows the transient response n Very Low Dropout Operation: 99% Duty Cycle to be optimized over a wide range of output capacitance and n Adjustable Soft-Start Current Ramping ESR values. The precision 0.8V reference and power good n Foldback Output Current Limiting output indicator are compatible with future microproces- n Latched Short-Circuit Shutdown with Defeat Option sor generations, and a wide 3.5V to 30V (36V maximum) n Output Overvoltage Protection input supply range encompasses all battery chemistries. n Remote Output Voltage Sense n A RUN/SS pin for each controller provides both soft-start Low Shutdown I : 20m A Q n and optional timed, short-circuit shutdown. Current 5V and 3.3V Standby Regulators n foldback limits MOSFET dissipation during short-circuit Selectable Constant Frequency or Burst Mode conditions when overcurrent latchoff is disabled. Output Operation n overvoltage protection circuitry latches on the bottom Available in 5mm 5mm QFN and MOSFET until V returns to normal. The FCB mode pin 28-Pin SSOP Packages OUT U can select among Burst Mode, constant frequency mode APPLICATIO S and continuous inductor current mode or regulate a secondary winding. The LTC1628-PG includes a power n Notebook and Palmtop Computers, PDAs good output pin that replaces the FLTCPL, fault coupling n Battery Chargers control pin of the LTC1628. n Portable Instruments , LTC and LT are registered trademarks of Linear Technology Corporation. n Battery-Operated Digital Devices OPTI-LOOP and Burst Mode are registered trademarks of Linear Technology Corporation. n DC Power Distribution Systems V IN 5.2V TO 28V C IN + TYPICAL APPLICATIO 1F 22F 4.7F D3 CERAMIC D4 50V V INTV IN CC CERAMIC M1 M3 TG1 TG2 L1 L2 C , 0.1F C , 0.1F B1 B2 6.3H BOOST1 BOOST2 6.3H SW1 SW2 LTC1628 M2 M4 BG1 BG2 D1 D2 SGND PGND + + SENSE1 SENSE2 R R SENSE1 1000pF SENSE2 1000pF 0.01 0.01 V SENSE1 SENSE2 V OUT1 OUT2 5V V V 3.3V OSENSE1 OSENSE2 5A 5A R2 R4 I I TH1 TH2 105k C C 63.4k C C1 C2 C OUT1 OUT + R1 RUN/SS1 RUN/SS2 R3 1% 220pF 220pF 1% 47F 56F 20k 20k R R 6V C1 C C C2 6V SS1 SS2 1% 1% 15k 15k SP 0.1F 0.1F SP M1, M2, M3, M4: FDS6680A 1628 F01 Figure 1. High Efficiency Dual 5V/3.3V Step-Down Converter 1628fb 1 + U ULTC1628/LTC1628-PG ABSOLUTE AXI U RATI GS (Note 1) Input Supply Voltage (V ).........................36V to 0.3V I I , V , V Voltages ...2.7V to 0.3V TH1, TH2 OSENSE1 OSENSE2 IN Top Side Driver Voltages Peak Output Current <10m s (TG1, TG2, BG1, BG2) ... 3A (BOOST1, BOOST2) ...................................42V to 0.3V INTV Peak Output Current ................................ 50mA CC Switch Voltage (SW1, SW2) .........................36V to 5V Operating Temperature Range INTV EXTV , RUN/SS1, RUN/SS2, (BOOST1-SW1), LTC1628C/LTC1628C-PG ........................ 0 C to 85 C CC, CC (BOOST2-SW2), PGOOD .............................7V to 0.3V LTC1628I/LTC1628I-PG ..................... 40 C to 85 C + + SENSE1 , SENSE2 , SENSE1 , Junction Temperature (Note 2)............................. 125 C SENSE2 Voltages ........................ (1.1)INTV to 0.3V Storage Temperature Range ................. 65 C to 150 C CC FREQSET, STBYMD, FCB, Lead Temperature (Soldering, 10 sec) FLTCPL Voltage ................................... INTV to 0.3V (G Package Only) .................................................. 300 C CC UUW PACKAGE/ORDER I FOR ATIO TOP VIEW TOP VIEW ORDER PART ORDER PART NUMBER NUMBER 1 28 FLTCPL* RUN/SS1 + 2 27 TG1 SENSE1 LTC1628CG LTC1628CUH 32 31 30 29 28 27 26 25 3 26 SW1 SENSE1 LTC1628IG V 1 24 BOOST1 LTC1628IUH OSENSE1 4 25 BOOST1 V OSENSE1 FREQSET 2 23 V LTC1628CG-PG IN 5 24 V FREQSET IN STBYMD 3 22 BG1 LTC1628IG-PG 6 23 BG1 STBYMD FCB 4 21 EXTV CC 7 22 EXTV FCB CC I 5 20 INTV TH1 CC 8 21 INTV I TH1 CC SGND 6 19 PGND 9 20 PGND SGND 3.3V 7 18 BG2 OUT UH PART 10 19 BG2 3.3V OUT I 8 17 BOOST2 TH2 MARKING 11 18 BOOST2 I TH2 9 10 11 12 13 14 15 16 12 17 SW2 V OSENSE2 1628 13 16 TG2 SENSE2 1628I + 14 15 RUN/SS2 SENSE2 UH PACKAGE G PACKAGE 32-LEAD (5mm 5mm) PLASTIC QFN 28-LEAD PLASTIC SSOP q = 34 C/W JA T = 125 C, q = 95 C/W JMAX JA EXPOSED PAD IS SGND (MUST BE SOLDERED TO PCB) *PGOOD ON THE LTC1628-PG Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25 C. V = 15V, V = 5V unless otherwise noted. A IN RUN/SS1, 2 SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Main Control Loops V Regulated Feedback Voltage (Note 3) I Voltage = 1.2V l 0.792 0.800 0.808 V OSENSE1, 2 TH1, 2 I Feedback Current (Note 3) 5 50 nA VOSENSE1, 2 V Reference Voltage Line Regulation V = 3.6V to 30V (Note 3) 0.002 0.02 %/V REFLNREG IN V Output Voltage Load Regulation (Note 3) LOADREG Measured in Servo Loop D I Voltage = 1.2V to 0.7V l 0.1 0.5 % TH Measured in Servo Loop D I Voltage = 1.2V to 2.0V l 0.1 0.5 % TH 1628fb 2 V NC OSENSE2 NC SENSE1 + SENSE2 SENSE1 + SENSE2 NC RUN/SS2 RUN/SS1 TG2 FLTCPL SW2 TG1 NC SW1 U WWW