LTC3851A

RECOMMENDED FOR NEW DESIGNS

Synchronous Step-Down Switching Regulator Controller

Data Sheet (Rev. B) Product Selection Table

Part Models: 22
1ku List Price: Starting From $2.09

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Overview

Wide V_IN Range: 4V to 38V Operation
R_SENSE or DCR Current Sensing
±1% Output Voltage Accuracy
Phase-Lockable Fixed Frequency: 250kHz to 750kHz
Dual N-Channel MOSFET Synchronous Drive
Very Low Dropout Operation: 99% Duty Cycle
Adjustable Output Voltage Soft-Start or Tracking
Output Current Foldback Limiting
Output Overvoltage Protection

5V Internal Regulator
OPTI-LOOP^® Compensation Minimizes C_OUT
Selectable Continuous, Pulse-Skipping or Burst Mode^® Operation at Light Loads
Low Shutdown I_Q: 20μA
V_OUT Range: 0.8V to 5.5V
Thermally Enhanced 16-Lead MSOP, 16-Lead Narrow SSOP or 3mm × 3mm QFN Package
AEC-Q100 Qualified for Automotive Applications

The LTC3851A is a high performance synchronous step-down switching regulator controller that drives an all N-channel synchronous power MOSFET stage. A constant frequency current mode architecture allows a phase-lockable frequency of up to 750kHz.

OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The LTC3851A features a precision 0.8V reference that is compatible with a wide 4V to 38V input supply range.

The TK/SS pin ramps the output voltage during start-up. Current foldback limits MOSFET heat dissipation during short-circuit conditions. The MODE/PLLIN pin selects among Burst Mode operation, pulse-skipping mode or continuous inductor current mode at light loads and allows the IC to be synchronized to an external clock. The LTC3851A contains an improved PLL compared to the LTC3851.

The LTC3851A-1 is a version with a power good output signal instead of adjustable current limit.


	Features
LTC3851	Not Recommended For New Designs
LTC3851-1	Not Recommended For New Designs
LTC3851A	Adjustable Current Limit
LTC3851A-1	PGOOD Output

Applications

Automotive Systems
Telecom Systems
Industrial Equipment
Distributed DC Power Systems

Part Models: 22
1ku List Price: Starting From $2.09

Documentation

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal. View our quality and reliability program and certifications for more information.

Part Model	Pin/Package Drawing	Documentation	CAD Symbols, Footprints, and 3D Models
LTC3851AEGN#PBF	16-Lead SSOP (Narrow 0.15 Inch)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AEGN#TRPBF	16-Lead SSOP (Narrow 0.15 Inch)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AEMSE#PBF	16-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AEMSE#TRPBF	16-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AEMSE#WPBF	16-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AEMSE#WTRPBF	16-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AEUD#PBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AEUD#TRPBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AHMSE#PBF	16-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AHMSE#TRPBF	16-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AHMSE#WPBF	16-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AHMSE#WTRPBF	16-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AIGN#PBF	16-Lead SSOP (Narrow 0.15 Inch)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AIGN#TRPBF	16-Lead SSOP (Narrow 0.15 Inch)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AIMSE#PBF	16-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AIMSE#TRPBF	16-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AIMSE#WPBF	16-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AIMSE#WTRPBF	16-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AIUD#PBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AIUD#TRPBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AMPMSE#PBF	16-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC3851AMPMSE#TRPBF	16-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys

Part Models	Product Lifecycle	PCN

Oct 3, 2024 - 24_0235 (QSOP/SSOP PKG) Migrating Bottom Trace Code Marking to Top Side Laser Marking
		PCN24_0235_Form Material_Report Other Delta Qualification Matrix
LTC3851AEGN#PBF	PRODUCTION
LTC3851AEGN#TRPBF	PRODUCTION
LTC3851AIGN#PBF	PRODUCTION
LTC3851AIGN#TRPBF	PRODUCTION
Oct 11, 2022 - 22_0235 Epoxy Change from Henkel 8290 to 8290A for GN Package
		PCN22_0235_Form Material_Report Qualification Results Summary Delta Qualification Matrix
LTC3851AEGN#PBF	PRODUCTION
LTC3851AEGN#TRPBF	PRODUCTION
LTC3851AIGN#PBF	PRODUCTION
LTC3851AIGN#TRPBF	PRODUCTION
Apr 6, 2022 - 22_0066 Laser Top Mark for 16QSOP Assembled in ADPG [PNG]
		PCN22_0066_Form Material_Report Delta Qualification Matrix
LTC3851AEGN#PBF	PRODUCTION
LTC3851AEGN#TRPBF	PRODUCTION
LTC3851AIGN#PBF	PRODUCTION
LTC3851AIGN#TRPBF	PRODUCTION
Nov 8, 2021 - 20_0245 Notification of Wafer Fab Location Change for 0.6µm BICMOS Process Devices from ADI Milpitas (Hillview) to Vanguard Int. (Taiwan)
		PCN20_0245_Form Material_Report Delta Qualification Matrix Other Qualification Results Summary
LTC3851AEGN#PBF	PRODUCTION
LTC3851AEGN#TRPBF	PRODUCTION
LTC3851AEMSE#PBF	PRODUCTION
LTC3851AEMSE#TRPBF	PRODUCTION
LTC3851AEUD#PBF	PRODUCTION
LTC3851AEUD#TRPBF	PRODUCTION
LTC3851AHMSE#PBF	PRODUCTION
LTC3851AHMSE#TRPBF	PRODUCTION
LTC3851AIGN#PBF	PRODUCTION
LTC3851AIGN#TRPBF	PRODUCTION
LTC3851AIMSE#PBF	PRODUCTION
LTC3851AIMSE#TRPBF	PRODUCTION
LTC3851AIUD#PBF	PRODUCTION
LTC3851AIUD#TRPBF	PRODUCTION
LTC3851AMPMSE#PBF	PRODUCTION
LTC3851AMPMSE#TRPBF	PRODUCTION
Jun 5, 2024 - 24_0003 Epoxy Change from Henkel 8290 to 8290A for MSOP Package (2)
		PCN24_0003_Form Material_Report Qualification Results Summary Delta Qualification Matrix
LTC3851AEMSE#PBF	PRODUCTION
LTC3851AEMSE#TRPBF	PRODUCTION
LTC3851AHMSE#PBF	PRODUCTION
LTC3851AHMSE#TRPBF	PRODUCTION
LTC3851AIMSE#PBF	PRODUCTION
LTC3851AIMSE#TRPBF	PRODUCTION
LTC3851AMPMSE#PBF	PRODUCTION
LTC3851AMPMSE#TRPBF	PRODUCTION
Feb 4, 2020 - 20_0132 Laser Top Mark for 16-Lead MSOP Packages Assembled in ADPG and UTAC
		PCN20_0132_Form Material_Report
LTC3851AEMSE#PBF	PRODUCTION
LTC3851AEMSE#TRPBF	PRODUCTION
LTC3851AHMSE#PBF	PRODUCTION
LTC3851AHMSE#TRPBF	PRODUCTION
LTC3851AIMSE#PBF	PRODUCTION
LTC3851AIMSE#TRPBF	PRODUCTION
LTC3851AMPMSE#PBF	PRODUCTION
LTC3851AMPMSE#TRPBF	PRODUCTION

This is the most up-to-date revision of the Data Sheet.

Software Resources

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Request a Driver/Software

Hardware Ecosystem

Parts	Product Life Cycle	Description
Circuit Monitors 1
LTC2960	RECOMMENDED FOR NEW DESIGNS	36V Nano-Current Two-Input Voltage Monitor
Oscillators 1
LTC6908		Resistor Set SOT-23 Oscillator with Spread Spectrum Modulation
Power System Management (PSM) & Sequencers 1
LTC2974	RECOMMENDED FOR NEW DESIGNS	4-Channel PMBus Power System Manager Featuring Accurate Output Current Measurement
Protection Switches & Controllers 1
LT4363	RECOMMENDED FOR NEW DESIGNS	High Voltage Surge Stopper with Current Limit

Tools & Simulations

LTspice 1

LTC3851A Demo Circuit - Synchronous Step-down DC/DC Converter (12V to 1.5V @ 15A)

Models for the following parts are available in LTspice:

LTC3851
LTC3851-1
LTC3851A
LTC3851A-1

LTpowerCAD 4

Design tools for the following parts are available in LTpowerCAD:

LTC3851A
LTC3851A-1

LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.

LTpowerCAD^® is a power supply design program which selects power stage components, provides detailed power efficiency, shows quick loop Bode plot stability and load transient analysis, and can export to LTspice for simulation.

Evaluation Kits

LTC3851AUED Demo Board with Adjustable ILIMIT | 4.5V ≤ VIN ≤ 14V, VOUT = 1.5V @ 15A

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Product Details

Demonstration circuit 1432A is a synchronous buck controller featuring the LTC3851AEUD/LTC3851AEUD-1. It operates with an input voltage from 4.5V to 14V and provides 1.5V at up to 15A at the output. The demo circuit is available in two versions. DC1432A-A is configured with LTC3851AEUD which provides ISET function, while the DC1432A-B is configured with LTC3851AEUD-1 which provides PGOOD function.

Resources

DC1432A - Schematic
12/21/2010

DC1432A - Demo Manual
12/21/2010

DC1432A - Design Files
12/21/2010

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