Datasheet LTC3728L, LTC3728LX (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Dual, 550kHz, 2-Phase Synchronous Regulators |
| Pages / Page | 38 / 1 — FeaTures. DescripTion. Dual, 180° Phased Controllers Reduce Required. … |
| File Format / Size | PDF / 466 Kb |
| 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
LTC3728L/LTC3728LX Dual, 550kHz, 2-Phase Synchronous Regulators
FeaTures DescripTion
n
Dual, 180° Phased Controllers Reduce Required
The LTC®3728L/LTC3728LX are dual high performance
Input Capacitance and Power Supply Induced Noise
step-down switching regulator controllers that drive all n
OPTI-LOOP
®
Compensation Minimizes COUT
N-channel synchronous power MOSFET stages. A constant- n
±1% Output Voltage Accuracy (LTC3728LC)
frequency, current mode architecture allows phase-lockable n
Power Good Output Voltage Indicator
frequency of up to 550kHz. Power loss and noise due to n
Phase-Lockable Fixed Frequency 250kHz to 550kHz
the ESR of the input capacitors are minimized by operating n Dual N-Channel MOSFET Synchronous Drive the two controller output stages out of phase. n Wide VIN Range: 4.5V to 28V 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 microproces- n Latched Short-Circuit Shutdown with Defeat Option sor generations, and a wide 4.5V to 28V (30V maximum) n Output Overvoltage Protection input supply range encompasses all battery chemistries. n Low Shutdown IQ: 20µA n A RUN/SS pin for each controller provides both soft- 5V and 3.3V Standby Regulators n start and optional timed, short-circuit shutdown. Current 3 Selectable Operating Modes: Constant-Frequency, foldback limits MOSFET dissipation during short-circuit Burst Mode® Operation and PWM n conditions when overcurrent latchoff is disabled. Output 5mm × 5mm QFN and 28-Lead Narrow SSOP overvoltage protection circuitry latches on the bottom Packages MOSFET until V
applicaTions
OUT returns to normal. The FCB mode pin can select among Burst Mode, constant-frequency n mode and continuous inductor current mode or regulate Notebook and Palmtop Computers a secondary winding. The LTC3728L/LTC3728LX include n Telecom Systems a power good output pin that indicates when both outputs n Portable Instruments are within 7.5% of their designed set point. n Battery-Operated Digital Devices L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode, OPTI-LOOP and PolyPhase n DC Power Distribution Systems are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
Typical applicaTion
VIN + 1µF CIN 5.2V TO 28V 4.7µF 22µF D3 CERAMIC D4 50V VIN PGOOD INTVCC CERAMIC M1 TG1 TG2 M2 L1 L2 3.2µH BOOST1 BOOST2 C 3.2µH B1, 0.1µF CB2, 0.1µF SW1 SW2 LTC3728L/ D1 BG1 LTC3728LX BG2 D2 fIN PLLIN PGND 500kHz SENSE1+ SENSE2+ RSENSE1 1000pF 1000pF RSENSE2 0.01Ω 0.01Ω SENSE1– SENSE2– VOUT1 VOSENSE1 VOSENSE2 VOUT2 5V R2 R4 3.3V ITH1 ITH2 5A 105k CC1 C 63.4k C2 5A 1% + COUT1 R1 220pF RUN/SS1 SGND RUN/SS2 220pF 1% COUT R3 + 47µF 56µF 6V 20k RC1 C C R SS1 SS2 C2 20k 6V SP 1% 15k 0.1µF 0.1µF 15k 1% SP M1, M2: FDS6982S
Figure 1. High Efficiency Dual 5V/3.3V Step-Down Converter
3728 F01 3728lxff 1 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagram Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts
FeaTures DescripTion
n
Dual, 180° Phased Controllers Reduce Required
The LTC®3728L/LTC3728LX are dual high performance
Input Capacitance and Power Supply Induced Noise
step-down switching regulator controllers that drive all n
OPTI-LOOP
®
Compensation Minimizes COUT
N-channel synchronous power MOSFET stages. A constant- n
±1% Output Voltage Accuracy (LTC3728LC)
frequency, current mode architecture allows phase-lockable n
Power Good Output Voltage Indicator
frequency of up to 550kHz. Power loss and noise due to n
Phase-Lockable Fixed Frequency 250kHz to 550kHz
the ESR of the input capacitors are minimized by operating n Dual N-Channel MOSFET Synchronous Drive the two controller output stages out of phase. n Wide VIN Range: 4.5V to 28V 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 microproces- n Latched Short-Circuit Shutdown with Defeat Option sor generations, and a wide 4.5V to 28V (30V maximum) n Output Overvoltage Protection input supply range encompasses all battery chemistries. n Low Shutdown IQ: 20µA n A RUN/SS pin for each controller provides both soft- 5V and 3.3V Standby Regulators n start and optional timed, short-circuit shutdown. Current 3 Selectable Operating Modes: Constant-Frequency, foldback limits MOSFET dissipation during short-circuit Burst Mode® Operation and PWM n conditions when overcurrent latchoff is disabled. Output 5mm × 5mm QFN and 28-Lead Narrow SSOP overvoltage protection circuitry latches on the bottom Packages MOSFET until V
applicaTions
OUT returns to normal. The FCB mode pin can select among Burst Mode, constant-frequency n mode and continuous inductor current mode or regulate Notebook and Palmtop Computers a secondary winding. The LTC3728L/LTC3728LX include n Telecom Systems a power good output pin that indicates when both outputs n Portable Instruments are within 7.5% of their designed set point. n Battery-Operated Digital Devices L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode, OPTI-LOOP and PolyPhase n DC Power Distribution Systems are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
Typical applicaTion
VIN + 1µF CIN 5.2V TO 28V 4.7µF 22µF D3 CERAMIC D4 50V VIN PGOOD INTVCC CERAMIC M1 TG1 TG2 M2 L1 L2 3.2µH BOOST1 BOOST2 C 3.2µH B1, 0.1µF CB2, 0.1µF SW1 SW2 LTC3728L/ D1 BG1 LTC3728LX BG2 D2 fIN PLLIN PGND 500kHz SENSE1+ SENSE2+ RSENSE1 1000pF 1000pF RSENSE2 0.01Ω 0.01Ω SENSE1– SENSE2– VOUT1 VOSENSE1 VOSENSE2 VOUT2 5V R2 R4 3.3V ITH1 ITH2 5A 105k CC1 C 63.4k C2 5A 1% + COUT1 R1 220pF RUN/SS1 SGND RUN/SS2 220pF 1% COUT R3 + 47µF 56µF 6V 20k RC1 C C R SS1 SS2 C2 20k 6V SP 1% 15k 0.1µF 0.1µF 15k 1% SP M1, M2: FDS6982S
Figure 1. High Efficiency Dual 5V/3.3V Step-Down Converter
3728 F01 3728lxff 1 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagram Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts
