LTC3728IUH

Product Summary

The LTC3728IUH is a Synchronous Step-Down Switching Regulator. The LTC3728IUH is a dual high performance step-down switching regulator controller that drives all N-channel synchronous power MOSFET stages. A constant frequency current mode architecture allows phase-lockable frequency of up to 550kHz. Power loss and noise due to the ESR of the input capacitors are minimized by operating the two controller output stages out of phase. OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The precision 0.8V reference and power good output indicator are compatible with future microprocessor generations, and a wide 3.5V to 30V (36V maximum) input supply range encompasses all battery chemistries. A RUN/SS pin for each controller provides both soft-start and optional timed, short-circuit shutdown. Current fold back limits MOSFET dissipation during short-circuit conditions when overcurrent latchoff is disabled. Output overvoltage protection circuitry latches on the bottom MOSFET until VOUT returns to normal. The FCB mode pin can select among Burst Mode, constant frequency mode and continuous inductor current mode or regulate a secondary winding. The LTC3728IUH includes a power good output pin that indicates when both outputs are within 7.5% of their designed set point. The applications of the LTC3728IUH include Notebook and Palmtop Computers, Telecom Systems, Portable Instruments, Battery-Operated Digital Devices and DC Power Distribution Systems.

Parametrics

LTC3728IUH absolute maximum ratings: (1)Input Supply Voltage (VIN): 36V to –0.3V; (2)Top Side Driver Voltages (BOOST1, BOOST2): 42V to –0.3V; (3)Switch Voltage (SW1, SW2): 36V to –5V; (4)INTVCC, EXTVCC, RUN/SS1, RUN/SS2, (BOOST1-SW1), (BOOST2-SW2), PGOOD: 7V to –0.3V; (5)SENSE1+, SENSE2 +, SENSE1–, SENSE2– Voltages: (1.1)INTVCC to –0.3V; (6)PLLIN, PLLFLTR, FCB, Voltage: INTVCC to –0.3V; (7)ITH1, ITH2, VOSENSE1, VOSENSE2 Voltages: 2.7V to –0.3V; (8)Peak Output Current <10μs (TG1, TG2, BG1, BG2): 3A; (9)INTVCC Peak Output Current: 50mA; (10)Operating Temperature Range (Note 7): –40℃ to 85℃; (11)Junction Temperature (Note 2): 125℃; (12)Storage Temperature Range: –65℃ to 125℃; (13)Lead Temperature (Soldering, 10 sec) (G Package Only): 300℃.

Features

LTC3728IUH features: (1)±1% Output Voltage Accuracy; (2)Power Good Output Voltage Indicator; (3)Phase-Lockable Fixed Frequency 250kHz to 550kHz; (4)Dual N-Channel MOSFET Synchronous Drive; (5)Wide VIN Range: 3.5V to 36V Operation; (6)Very Low Dropout Operation: 99% Duty Cycle; (7)Adjustable Soft-Start Current Ramping; (8)Foldback Output Current Limiting; (9)Latched Short-Circuit Shutdown with Defeat Option; (10)Output Overvoltage Protection; (11)Remote Output Voltage Sense; (12)Low Shutdown IQ: 20μA; (13)5V and 3.3V Regulators; (14)3 Selectable Operating Modes: Constant Frequency, Burst ModeR Operation and PWM; (15)Available in 32-Pin 5mm x 5mm QFN and 28-Pin SSOP Packages.

Diagrams