Datasheet LTC3851A (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Synchronous Step-Down Switching Regulator Controller |
| Pages / Page | 30 / 1 — FeaTures. DescripTion. Wide VIN Range: 4V to 38V Operation. RSENSE or DCR … |
| File Format / Size | PDF / 445 Kb |
| Document Language | English |
FeaTures. DescripTion. Wide VIN Range: 4V to 38V Operation. RSENSE or DCR Current Sensing. ±1% Output Voltage Accuracy
Model Line for this Datasheet
- LTC3851AEGN#PBF LTC3851AEGN#PBF LTC3851AEGN#TRPBF LTC3851AEGN#TRPBF LTC3851AEMSE#PBF LTC3851AEMSE#PBF LTC3851AEMSE#TRPBF LTC3851AEMSE#TRPBF LTC3851AEUD#PBF LTC3851AEUD#PBF LTC3851AEUD#TRPBF LTC3851AEUD#TRPBF LTC3851AHMSE#PBF LTC3851AHMSE#PBF LTC3851AHMSE#TRPBF LTC3851AHMSE#TRPBF LTC3851AIGN#PBF LTC3851AIGN#PBF LTC3851AIGN#TRPBF LTC3851AIGN#TRPBF LTC3851AIMSE#PBF LTC3851AIMSE#PBF LTC3851AIMSE#TRPBF LTC3851AIMSE#TRPBF LTC3851AIUD#PBF LTC3851AIUD#PBF LTC3851AIUD#TRPBF LTC3851AIUD#TRPBF LTC3851AMPMSE#PBF LTC3851AMPMSE#PBF LTC3851AMPMSE#TRPBF LTC3851AMPMSE#TRPBF
Text Version of Document
LTC3851A Synchronous Step-Down Switching Regulator Controller
FeaTures DescripTion
n
Wide VIN Range: 4V to 38V Operation
The LTC®3851A is a high performance synchronous n
RSENSE or DCR Current Sensing
step-down switching regulator controller that drives n
±1% Output Voltage Accuracy
an all N-channel synchronous power MOSFET stage. A n
Phase-Lockable Fixed Frequency: 250kHz to 750kHz
con stant frequency current mode architecture allows a n Dual N-Channel MOSFET Synchronous Drive phase-lockable frequency of up to 750kHz. n Very Low Dropout Operation: 99% Duty Cycle OPTI-LOOP compensation allows the transient response n Adjustable Output Voltage Soft-Start or Tracking to be optimized over a wide range of output capacitance n Output Current Foldback Limiting and ESR values. The LTC3851A features a precision 0.8V n Output Overvoltage Protection reference that is compatible with a wide 4V to 38V input n 5V Internal Regulator supply range. n OPTI-LOOP® Compensation Minimizes COUT n Selectable Continuous, Pulse-Skipping or The TK/SS pin ramps the output voltage during start-up. Burst Mode® Operation at Light Loads Current foldback limits MOSFET heat dissipation during n Low Shutdown I short-circuit conditions. The MODE/PLLIN pin selects Q: 20µA n V among Burst Mode operation, pulse-skipping mode or OUT Range: 0.8V to 5.5V n Thermally Enhanced 16-Lead MSOP, 16-Lead Narrow continuous inductor current mode at light loads and al- SSOP or 3mm × 3mm QFN Package lows the IC to be synchronized to an external clock. The LTC3851A contains an improved PLL compared to the
applicaTions
LTC3851. n Automotive Systems The LTC3851A-1 is a version with a power good output n Telecom Systems signal instead of adjustable current limit. n Industrial Equipment L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, Linear Technology and the Linear logo are registered trademarks and No R n Distributed DC Power Systems SENSE, UltraFast are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5408150, 5481178, 5705919, 5929620, 6304066, 6498466, 6580258, 6611131.
Typical applicaTion High Efficiency Synchronous Step-Down Converter Efficiency and Power Loss vs Load Current
I VIN LIM VIN 100 10000 22µF 4.5V TO 36V V FREQ/PLLFLTR TG IN = 12V 0.68µH 95 V V OUT = 3.3V OUT 82.5k 0.1µF RUN SW 3.3V 90 LTC3851A 0.1µF 15A EFFICIENCY POWER LOSS (mW) TK/SS BOOST 85 330µF 1000 0.1µF 3.01k ×2 80 INTV 75 CC POWER LOSS 2200pF 4.7µF 70 ITH BG EFFICIENCY (%) 100 GND 65 15k 330pF 60 SENSE+ 55 MODE/PLLIN 0.047µF 30.1k SENSE– 154k 50 10 10 100 1000 10000 100000 VFB LOAD CURRENT (mA) 48.7k 3851A TA01b 3851A TA01a 3851afa 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
Wide VIN Range: 4V to 38V Operation
The LTC®3851A is a high performance synchronous n
RSENSE or DCR Current Sensing
step-down switching regulator controller that drives n
±1% Output Voltage Accuracy
an all N-channel synchronous power MOSFET stage. A n
Phase-Lockable Fixed Frequency: 250kHz to 750kHz
con stant frequency current mode architecture allows a n Dual N-Channel MOSFET Synchronous Drive phase-lockable frequency of up to 750kHz. n Very Low Dropout Operation: 99% Duty Cycle OPTI-LOOP compensation allows the transient response n Adjustable Output Voltage Soft-Start or Tracking to be optimized over a wide range of output capacitance n Output Current Foldback Limiting and ESR values. The LTC3851A features a precision 0.8V n Output Overvoltage Protection reference that is compatible with a wide 4V to 38V input n 5V Internal Regulator supply range. n OPTI-LOOP® Compensation Minimizes COUT n Selectable Continuous, Pulse-Skipping or The TK/SS pin ramps the output voltage during start-up. Burst Mode® Operation at Light Loads Current foldback limits MOSFET heat dissipation during n Low Shutdown I short-circuit conditions. The MODE/PLLIN pin selects Q: 20µA n V among Burst Mode operation, pulse-skipping mode or OUT Range: 0.8V to 5.5V n Thermally Enhanced 16-Lead MSOP, 16-Lead Narrow continuous inductor current mode at light loads and al- SSOP or 3mm × 3mm QFN Package lows the IC to be synchronized to an external clock. The LTC3851A contains an improved PLL compared to the
applicaTions
LTC3851. n Automotive Systems The LTC3851A-1 is a version with a power good output n Telecom Systems signal instead of adjustable current limit. n Industrial Equipment L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, Linear Technology and the Linear logo are registered trademarks and No R n Distributed DC Power Systems SENSE, UltraFast are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5408150, 5481178, 5705919, 5929620, 6304066, 6498466, 6580258, 6611131.
Typical applicaTion High Efficiency Synchronous Step-Down Converter Efficiency and Power Loss vs Load Current
I VIN LIM VIN 100 10000 22µF 4.5V TO 36V V FREQ/PLLFLTR TG IN = 12V 0.68µH 95 V V OUT = 3.3V OUT 82.5k 0.1µF RUN SW 3.3V 90 LTC3851A 0.1µF 15A EFFICIENCY POWER LOSS (mW) TK/SS BOOST 85 330µF 1000 0.1µF 3.01k ×2 80 INTV 75 CC POWER LOSS 2200pF 4.7µF 70 ITH BG EFFICIENCY (%) 100 GND 65 15k 330pF 60 SENSE+ 55 MODE/PLLIN 0.047µF 30.1k SENSE– 154k 50 10 10 100 1000 10000 100000 VFB LOAD CURRENT (mA) 48.7k 3851A TA01b 3851A TA01a 3851afa 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
