Datasheet LTC3851A-1 (Analog Devices)

ManufacturerAnalog Devices
DescriptionSynchronous Step-Down Switching Regulator Controller
Pages / Page30 / 1 — FeaTures. DescripTion. Wide VIN Range: 4V to 38V Operation. RSENSE or DCR …
File Format / SizePDF / 442 Kb
Document Languageenglish

FeaTures. DescripTion. Wide VIN Range: 4V to 38V Operation. RSENSE or DCR Current Sensing. ±1% Output Voltage Accuracy

Datasheet LTC3851A-1 Analog Devices

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LTC3851A-1 Synchronous Step-Down Switching Regulator Controller
FeaTures DescripTion
Wide VIN Range: 4V to 38V Operation
The LTC®3851A-1 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
Power Good Output Voltage Monitor
con stant frequency current mode architecture allows a n
Phase-Lockable Fixed Frequency: 250kHz to 750kHz
phase-lockable frequency of up to 750kHz. n Dual N-Channel MOSFET Synchronous Drive OPTI-LOOP compensation al ows the transient response n Very Low Dropout Operation: 99% Duty Cycle to be optimized over a wide range of output capacitance n Adjustable Output Voltage Soft-Start or Tracking and ESR values. The LTC3851A-1 features a precision 0.8V n Output Current Foldback Limiting reference and a power good indicator. A wide 4V to 38V n Output Overvoltage Protection (40V absolute maximum) input supply range encompasses n OPTI-LOOP® Compensation Minimizes COUT most battery configurations and intermediate bus voltages. n Selectable Continuous, Pulse-Skipping or Burst Mode® Operation at Light Loads The TK/SS pin ramps the output voltage during start-up and n Low Shutdown I shutdown with coincident or ratiometric tracking. Current Q: 20µA n V foldback limits MOSFET heat dissipation during short- OUT Range: 0.8V to 5.5V n Thermally Enhanced 16-Lead MSOP circuit conditions. The MODE/PLLIN pin selects among or 3mm × 3mm QFN Package Burst Mode operation, pulse-skipping mode or continu- ous inductor current mode at light loads and allows the IC
to be synchronized to an external clock. The LTC3851A-1 contains an improved PLL compared to the LTC3851-1. n Automotive Systems The LTC3851A-1 is identical to the LTC3851A except that n Telecom Systems the ILIM pin is replaced by PGOOD. n Industrial Equipment L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, Linear Technology and the Linear logo are registered n Distributed DC Power Systems trademarks and No RSENSE, 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
100k INTV VIN CC PGO0D VIN 100 10000 22µF 4.5V TO 38V VIN = 12V FREQ/PLLFLTR TG 95 VOUT = 3.3V 0.68µH V 0.1µF OUT EFFICIENCY 82.5k RUN SW 3.3V 90 LTC3851A-1 0.1µF 15A POWER LOSS (mW) 85 TK/SS BOOST 1000 330µF 0.1µF 3.01k ×2 80 POWER LOSS 75 INTVCC 2200pF 4.7µF 70 I EFFICIENCY (%) TH BG 100 65 GND 15k 330pF 60 SENSE+ 55 MODE/PLLIN 0.047µF 30.1k 50 10 SENSE– 154k 10 100 1000 10000 100000 VFB LOAD CURRENT (mA) 48.7k 3851A1 TA01b 3851A1 TA01a 3851a1fa 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
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