LTC3850

Dual, 2-Phase Synchronous Step-Down Switching Controller

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Overview

Features and Benefits
Product Details

Features and Benefits

Dual, 180° Phased Controllers Reduce Required Input Capacitance and Power Supply Induced Noise
High Efficiency: Up to 95%
R_SENSE or DCR Current Sensing
±1% 0.8V Output Voltage Accuracy
Phase-Lockable Fixed Frequency 250kHz to 780kHz
Supports Pre-Biased Output

Dual N-Channel MOSFET Synchronous Drive
Wide V_IN Range: 4V to 24V (30V for LTC3850I) Operation
Adjustable Soft-Start Current Ramping or Tracking
Foldback Output Current Limiting
Power Good Output Voltage Monitor
28-Pin 4mm × 4mm, 4mm × 5mm QFN and Narrow SSOP Packages
AEC-Q100 Qualified for Automotive Applications

Product Details

The LTC3850 is a high performance dual synchronous step-down switching regulator controller that drives all N-channel power MOSFET stages. A constant-frequency current mode architecture allows a phase-lockable frequency of up to 780kHz. Power loss and supply noise are minimized by operating the two controller output stages out of phase.

OPTI-LOOP^® compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The LTC3850 features a precision 0.8V reference and a power good output indicator. A wide 4V to 24V (28V maximum/30V for LTC3850I) input supply range encompasses most battery chemistries and intermediate bus voltages.

Independent TK/SS pins for each controller ramp the output voltages 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 and allows the IC to be synchronized to an external clock.

The LTC3850 is available in low profile 28-pin 4mm × 4mm, 4mm × 5mm QFN and narrow SSOP packages.


	Features
LTC3850	SSOP-28 and QFN-28 Packages
LTC3850-1	ILIM function replaced with an EXTVCC function, SSOP-28 package only
LTC3850-2	The LTC3850-2 is identical to the LTC3850-1 SSOP-28, except they have different pin-outs

Applications

Notebook and Palmtop Computers
Portable Instruments
Battery-Operated Digital Devices
DC Power Distribution Systems

Product Categories

Power Management
- External Power Switch Buck Controllers
- Multiple Output Buck Regulators

Markets and Technologies

Data Center

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Product Lifecycle Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Evaluation Kits (6)

DC1185A-A

LTC3850EUF Demo Board | 4.5V ≤ V_IN ≤ 14V; V_OUT1: 2V @ 10A, V_OUT2: 1.8V @ 10A

DC1231A-B

LTC3850EGN Demo Board | 6.5V < V_IN < 24V, V_OUT1= 3.3V/5A, V_OUT2= 2.5V/5A, with DCR Current Sense

DC1231A-A

LTC3850EGN Demo Board | 6.5V < V_IN < 24V, V_OUT1= 3.3V/5A, V_OUT2= 2.5V/5A

DC1185B-A

LTC3850EUF Demo Board | 4.5V ≤ V_IN ≤ 14V; V_OUT1: 2V @ 10A, V_OUT2: 1.8V @ 10A

DC1185B-B

LTC3850EUF Demo Board | 4.5V ≤ V_IN ≤ 14V; V_OUT1: 1.5V @ 15A, V_OUT2: 1.2V @ 15A

DC1126A

LTC3850EUF Demo Board | 6.5V ≤ V_IN ≤ 14V, V_OUT = 3.3V @ 5A & 2.5V @ 5A

DC1185A-A

View Detailed Evaluation Kit Information

Demonstration circuit 1185 is a dual phase/dual output synchronous buck converter featuring the LTC3850EUF. The demo board comes in two versions. The output voltages for version -A are 2.0V/10A and 1.8V/10A and the output voltages for version -B are 1.5V/15A and 1.2V/15A. The input voltage range is 6.5V to 14V for both versions. For applications that have a 5V ±0.5V input, the board has an optional resistor to tie the INTVCC pin to the V_IN pin.

Resources

DC1231A-B

View Detailed Evaluation Kit Information

Demonstration circuit 1231A is a Dual Output, Dual Phase 5A Synchronous Buck Converter featuring the LTC3850EGN. The entire circuit, including the bulk output capacitors, fit within a 1.04 × 0.94 area on all layers. The package style for the LTC3850EGN is a 28-lead narrow plastic SSOP. The main features of the board include rail tracking, an internal 5V linear regulator for bias, RUN pins for each output and a PGOOD signal and a Mode selector that allow the converter to run in CCM, pulse skip or Burst Mode operation. Synchronization to an external clock is also possible through some minor component changes. Two versions of the board are available. DC-1231A-A has an on-board sense resistor for current feedback, while the DC1231A-B is configured with a DCR sense circuit that allows the converter to use the inductors DCR as the sense element instead of the on-board sense resistors to save cost and board space and improves efficiency.

Resources

DC1231A-A

View Detailed Evaluation Kit Information

Resources

DC1185B-A

View Detailed Evaluation Kit Information

Resources

DC1185B-B

View Detailed Evaluation Kit Information

Demonstration circuit 1185 is a dual phase/dual output synchronous buck converter featuring the LTC3850EUF. The demo board comes in two versions. The output voltages for version -A are 2.0V/10A and 1.8V/10A and the output voltages for version -B are 1.5V/15A and 1.2V/15A. The input voltage range is 6.5V to 14V for both versions. For applications that have a 5V ± 0.5V input, the board has an optional resistor to tie the INTVCC pin to the V_IN pin.

Resources

DC1126A

View Detailed Evaluation Kit Information

Demonstration circuit 1126 is a high density dual output (3.3V/5A and 2.5V/5A) step down converter featuring the LTC3850EUF. The input voltage range is 6.5V to 14V. For applications that have a 5V +/- 0.5V input, the board has an optional resistor to tie the INTVCC pin to the V_IN pin.

An optional DCR sense circuit allows the converter to use the inductors DCR as the sense element instead of the on-board sense resistors to save cost and board space and to improve efficiency.

Resources

Documentation & Resources

Data Sheets

LTC3850: Dual, 2-Phase Synchronous Step-Down Switching Controller Data Sheet (Rev. D)
3/4/2011
PDF

Reliability Data

R526 Reliability Data
3/26/2018
PDF

User Guides

Videos

Voltage vs. Current Mode Control Curent Sharing in a PolyPhase DC/DC Converter - LTC3731, LTC3853, LTC3850
10/15/2018

Technical Articles

3-Phase Synchronous Step-Down DC/DC Controller with Stage Shedding, Active Voltage Positioning and Nonlinear Control for High Efficiency and Fast Transient Response
10/1/2011 LT Journal
6mm × 6mm DC/DC Controller for High Current DCR Sensing Applications
4/1/2010 LT Journal
2-Phase Synchronous Buck Controller Delivers Maximum Features in Minimum Footprint
10/1/2007 LT Journal

Tools & Simulations

LTspice

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.

To launch ready-to-run LTspice demonstration circuits for this part:

Step 1: Download and install LTspice on your computer.

Step 2: Click on the link in the section below to download a demonstration circuit.

Step 3: If LTspice does not automatically open after clicking the link below, you can instead run the simulation by right clicking on the link and selecting “Save Target As.” After saving the file to your computer, start LTspice and open the demonstration circuit by selecting ‘Open’ from the ‘File’ menu.

LTspice downloads and documentation

LTspice Simulations

LTC3850 Demo Circuit - Dual, 2-Phase Synchronous step-down Controller (12V to 2.5V @ 10A & 1.2V @ 10A)

Models for the following parts are available in LTspice:

LTC3850

LTC3850-1

LTC3850-2

LTpowerCAD

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.

To open the project file for this circuit:

Step 1: Download and install LTpowerCAD on your computer.

Step 2: Click on the link(s) in the section below to download part-specific project files.

Step 3: If the project file doesn't run, right-click the link and select "Save Target As." Then start the LTpowerCAD tool and open the project file by selecing "Open Project" from the "File" menu.

LTpowerCAD download and documentation

LTpowerCAD Project Files

LTC3850 Project - Dual, 2-Phase Synchronous Step-Down Supply with Rsense Current Sensing (6.5-14V to 2V @ 10A & 1.8V @ 10A)

LTC3850 Project - Dual, 2-Phase Synchronous Step-Down Supply with Inductor DCR Current Sensing (6.5-14V to 1.5V @ 15A & 1.2V @ 15A)

Design tools for the following parts are available in LTpowerCAD:

LTC3850

Reference Designs (1)

Altera Cyclone IV GX FPGA Development Kit

View Detailed Reference Design Information

Features & Benefits

Analog Devices has worked closely with FPGA and processor manufacturers to develop verified power solutions that optimize cost, size and efficiency in high performance applications
Our reference designs are supported by an intuitive design tool set and IP
Our team can provide designs for quick prototypes that can speed time to market in the most complex applications

Parts Used

Product Recommendations

LTC3850 Companion Parts

Recommended Related Parts

LTC3880, LT4363, LTC2960.

Recommended Suggested Oscillator

LTC6909.

Design Resources

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 Number	Material Declaration	Reliability Data	Pin/Package Drawing	CAD Symbols, Footprints & 3D Models
LTC3850EGN#PBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850EGN#TRPBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850EGN#WPBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850EGN#WTRPBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850EGN-1#PBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850EGN-1#TRPBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850EGN-1#WPBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850EGN-1#WTRPBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850EUF#PBF	Material Declaration	Reliability Data	28-Lead QFN (4mm x 5mm x 0.75mm w/ EP)	Ultra Librarian SamacSys
LTC3850EUF#TRPBF	Material Declaration	Reliability Data	28-Lead QFN (4mm x 5mm x 0.75mm w/ EP)	Ultra Librarian SamacSys
LTC3850EUFD#PBF	Material Declaration	Reliability Data	28-Lead QFN (4mm x 5mm x 0.75mm w/ EP)	Ultra Librarian SamacSys
LTC3850EUFD#TRPBF	Material Declaration	Reliability Data	28-Lead QFN (4mm x 5mm x 0.75mm w/ EP)	Ultra Librarian SamacSys
LTC3850IGN#PBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850IGN#TRPBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850IGN#WPBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850IGN#WTRPBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850IGN-1#PBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850IGN-1#TRPBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850IGN-1#WPBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850IGN-1#WTRPBF	Material Declaration	Reliability Data	28-Lead SSOP (Narrow 0.15 Inch)	Ultra Librarian SamacSys
LTC3850IUF#PBF	Material Declaration	Reliability Data	28-Lead QFN (4mm x 5mm x 0.75mm w/ EP)	Ultra Librarian SamacSys
LTC3850IUF#TRPBF	Material Declaration	Reliability Data	28-Lead QFN (4mm x 5mm x 0.75mm w/ EP)	Ultra Librarian SamacSys
LTC3850IUFD#PBF	Material Declaration	Reliability Data	28-Lead QFN (4mm x 5mm x 0.75mm w/ EP)	Ultra Librarian SamacSys
LTC3850IUFD#TRPBF	Material Declaration	Reliability Data	28-Lead QFN (4mm x 5mm x 0.75mm w/ EP)	Ultra Librarian SamacSys
Wafer Fabrication Data		R526 Reliability Data

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Evaluation Boards

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Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.