Datasheet LTC3728 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Dual, 550kHz, 2-Phase Synchronous Step-Down Switching Regulator |
| Pages / Page | 36 / 1 — FEATURES. DESCRIPTION. Dual, 180° Phased Controllers Reduce Required. … |
| File Format / Size | PDF / 1.7 Mb |
| Document Language | English |
FEATURES. DESCRIPTION. Dual, 180° Phased Controllers Reduce Required. Input Capacitance and Power Supply Induced Noise
Model Line for this Datasheet
Text Version of Document
LTC3728 Dual, 550kHz, 2-Phase Synchronous Step-Down Switching Regulator
FEATURES DESCRIPTION
n
Dual, 180° Phased Controllers Reduce Required
The LTC®3728 is a dual high performance step-down
Input Capacitance and Power Supply Induced Noise
switching regulator controller that drives all N-channel n
OPTI-LOOP
®
Compensation Minimizes COUT
synchronous power MOSFET stages. A constant-frequency n
±1% Output Voltage Accuracy
current mode architecture allows phase-lockable frequency n
Power Good Output Voltage Indicator
of up to 550kHz. Power loss and noise due to the ESR of n
Phase-Lockable Fixed Frequency 250kHz to 550kHz
the input capacitors are minimized by operating the two n Dual N-Channel MOSFET Synchronous Drive controller output stages out of phase. n Wide VIN Range: 3.5V to 36V Operation OPTI-LOOP compensation allows the transient response to n Very Low Dropout Operation: 99% Duty Cycle 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 microprocessor n Latched Short-Circuit Shutdown with Defeat Option generations, and a wide 3.5V to 30V (36V maximum) input n Output Overvoltage Protection supply range encompasses all battery chemistries. n Remote Output Voltage Sense n Low Shutdown I A RUN/SS pin for each controller provides both soft- Q: 20μA n 5V and 3.3V Regulators start and optional timed, short-circuit shutdown. Current n 3 Selectable Operating Modes: Constant-Frequency, foldback limits MOSFET dissipation during short-circuit Burst Mode® Operation and PWM conditions when overcurrent latchoff is disabled. Output n Available in 32-Pin 5mm × 5mm QFN and overvoltage protection circuitry latches on the bottom 28-Pin SSOP Packages MOSFET until VOUT returns to normal. The FCB mode pin can select among Burst Mode, constant-frequency
APPLICATIONS
mode and continuous inductor current mode or regulate n Notebook and Palmtop Computers a secondary winding. The LTC3728 includes a power good n Telecom Systems output pin that indicates when both outputs are within n Portable Instruments 7.5% of their designed set point. n Battery-Operated Digital Devices L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode and OPTI-LOOP are n DC Power Distribution Systems registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 5929620, 6177787, 6144194, 6100678, 5408150, 6580258, 5705919.
TYPICAL APPLICATION
VIN + C 5.2V TO 28V 4.7μF IN D3 1μF 22μF VIN PGOOD INTVCC D4 M1 M2 50V TG1 TG2 L1 L2 BOOST1 BOOST2 3.2μH C 3.2μH B1, 0.1μF CB2, 0.1μF SW1 SW2 LTC3728 BG1 BG2 fIN PLLIN PGND 500kHz SENSE1+ SENSE2+ R R SENSE1 1000pF 1000pF SENSE2 0.01Ω 0.01Ω SENSE1– SENSE2– VOUT1 V VOUT2 OSENSE1 VOSENSE2 R2 5V R4 3.3V I C 105k C TH1 ITH2 5A OUT1 C1 C 63.4k C + C2 OUT 5A 47 1% RUN/SS1 RUN/SS2 μF R1 220pF SGND 220pF R3 1% 56 + μF 6V 20k RC1 C C 20k 6V SS1 SS2 RC2 SP 1% 15k 0.1 0.1 1% μF μF SP 15k M1, M2: FDS6982S 3728 F01
Figure 1. High Effi ciency Dual 5V/3.3V Step-Down Converter
3728fg 1
FEATURES DESCRIPTION
n
Dual, 180° Phased Controllers Reduce Required
The LTC®3728 is a dual high performance step-down
Input Capacitance and Power Supply Induced Noise
switching regulator controller that drives all N-channel n
OPTI-LOOP
®
Compensation Minimizes COUT
synchronous power MOSFET stages. A constant-frequency n
±1% Output Voltage Accuracy
current mode architecture allows phase-lockable frequency n
Power Good Output Voltage Indicator
of up to 550kHz. Power loss and noise due to the ESR of n
Phase-Lockable Fixed Frequency 250kHz to 550kHz
the input capacitors are minimized by operating the two n Dual N-Channel MOSFET Synchronous Drive controller output stages out of phase. n Wide VIN Range: 3.5V to 36V Operation OPTI-LOOP compensation allows the transient response to n Very Low Dropout Operation: 99% Duty Cycle 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 microprocessor n Latched Short-Circuit Shutdown with Defeat Option generations, and a wide 3.5V to 30V (36V maximum) input n Output Overvoltage Protection supply range encompasses all battery chemistries. n Remote Output Voltage Sense n Low Shutdown I A RUN/SS pin for each controller provides both soft- Q: 20μA n 5V and 3.3V Regulators start and optional timed, short-circuit shutdown. Current n 3 Selectable Operating Modes: Constant-Frequency, foldback limits MOSFET dissipation during short-circuit Burst Mode® Operation and PWM conditions when overcurrent latchoff is disabled. Output n Available in 32-Pin 5mm × 5mm QFN and overvoltage protection circuitry latches on the bottom 28-Pin SSOP Packages MOSFET until VOUT returns to normal. The FCB mode pin can select among Burst Mode, constant-frequency
APPLICATIONS
mode and continuous inductor current mode or regulate n Notebook and Palmtop Computers a secondary winding. The LTC3728 includes a power good n Telecom Systems output pin that indicates when both outputs are within n Portable Instruments 7.5% of their designed set point. n Battery-Operated Digital Devices L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode and OPTI-LOOP are n DC Power Distribution Systems registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 5929620, 6177787, 6144194, 6100678, 5408150, 6580258, 5705919.
TYPICAL APPLICATION
VIN + C 5.2V TO 28V 4.7μF IN D3 1μF 22μF VIN PGOOD INTVCC D4 M1 M2 50V TG1 TG2 L1 L2 BOOST1 BOOST2 3.2μH C 3.2μH B1, 0.1μF CB2, 0.1μF SW1 SW2 LTC3728 BG1 BG2 fIN PLLIN PGND 500kHz SENSE1+ SENSE2+ R R SENSE1 1000pF 1000pF SENSE2 0.01Ω 0.01Ω SENSE1– SENSE2– VOUT1 V VOUT2 OSENSE1 VOSENSE2 R2 5V R4 3.3V I C 105k C TH1 ITH2 5A OUT1 C1 C 63.4k C + C2 OUT 5A 47 1% RUN/SS1 RUN/SS2 μF R1 220pF SGND 220pF R3 1% 56 + μF 6V 20k RC1 C C 20k 6V SS1 SS2 RC2 SP 1% 15k 0.1 0.1 1% μF μF SP 15k M1, M2: FDS6982S 3728 F01
Figure 1. High Effi ciency Dual 5V/3.3V Step-Down Converter
3728fg 1
