LTC3855 - Dual, Multiphase Synchronous DC/DC Controller with Differential Remote Sense
Features
- Dual, 180° Phased Controllers Reduce Required Input Capacitance and Power Supply Induced Noise
- High Efficiency: Up to 95%
- RSENSE or DCR Current Sensing
- Programmable DCR Temperature Compensation
- ±0.75% 0.6V Output Voltage Accuracy
- Phase-Lockable Fixed Frequency 250kHz to 770kHz
- True Remote Sensing Differential Amplifier
- Dual N-Channel MOSFET Synchronous Drive
- Wide VIN Range: 4.5V to 38V
- VOUT Range: 0.6V to 12.5V without Differential Amplifier
- VOUT Range: 0.6V to 3.3V with Differential Amplifier
- Clock Input and Output for Up to 12-Phase Operation
- Adjustable Soft-Start or VOUT Tracking
- Foldback Output Current Limiting
- Output Overvoltage Protection
- 40-Pin (6mm × 6mm) QFN and 38-Lead FE Packages
AEC-Q100 data available for specific packages
Typical Application
Description
The LTC3855 is a dual PolyPhase current mode synchronous step-down switching regulator controller that drives all N-channel power MOSFET stages. It includes a high speed differential remote sense amplifier. The maximum current sense voltage is programmable for either 30mV, 50mV or 75mV, allowing the use of either the inductor DCR or a discrete sense resistor as the sensing element.
The LTC3855 features a precision 0.6V reference and can produce output voltages up to 12.5V. A wide 4.5V to 38V input supply range encompasses most intermediate bus voltages and battery chemistries. Power loss and supply noise are minimized by operating the two controller output stages out of phase. Burst Mode operation, continuous or pulse-skipping modes are supported.
The LTC3855 can be configured for up to 12-phase operation, has DCR temperature compensation, two power good signals and two current limit set pins. The LTC3855 is available in low profile 40-pin 6mm × 6mm QFN and 38-lead exposed pad FE packages.
Packaging
CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.
For complete and up to date package information and drawings, please refer to our packaging page
| Part Number | Package | Code | Temp | Package Drawing |
RoHS |
|---|---|---|---|---|---|
| LTC3855EFE#PBF | TSSOP-38 | FE | E | 05-08-1772 | Yes |
| LTC3855EFE#TRPBF | TSSOP-38 | FE | E | 05-08-1772 | Yes |
| LTC3855EUJ#PBF | 6x6 QFN-40 | UJ | E | 05-08-1728 | Yes |
| LTC3855EUJ#TRPBF | 6x6 QFN-40 | UJ | E | 05-08-1728 | Yes |
| LTC3855IFE#PBF | TSSOP-38 | FE | I | 05-08-1772 | Yes |
| LTC3855IFE#TRPBF | TSSOP-38 | FE | I | 05-08-1772 | Yes |
| LTC3855IUJ#PBF | 6x6 QFN-40 | UJ | I | 05-08-1728 | Yes |
| LTC3855IUJ#TRPBF | 6x6 QFN-40 | UJ | I | 05-08-1728 | Yes |
Order Info
- Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
- Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
- Please refer to our general ordering information or the product datasheet for more details
Package Variations and Pricing
| Part Number | Package | Temp | Price (1-99) |
Price (1k)* |
RoHS | |
|---|---|---|---|---|---|---|
| LTC3855EFE#PBF | TSSOP-38 | E | $4.86 | $3.40 | Yes | |
| LTC3855EFE#TRPBF | TSSOP-38 | E | $3.46 | Yes | ||
| LTC3855EUJ#PBF | 6x6 QFN-40 | E | $4.54 | $3.18 | Yes | |
| LTC3855EUJ#TRPBF | 6x6 QFN-40 | E | $3.24 | Yes | ||
| LTC3855IFE#PBF | TSSOP-38 | I | $5.54 | $3.88 | Yes | |
| LTC3855IFE#TRPBF | TSSOP-38 | I | $3.94 | Yes | ||
| LTC3855IUJ#PBF | 6x6 QFN-40 | I | $5.13 | $3.59 | Yes | |
| LTC3855IUJ#TRPBF | 6x6 QFN-40 | I | $3.65 | Yes | ||
| Buy Now • Request Samples | ||||||
Demo Boards
Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.| Part Number | Description | Price | Documentation |
|---|---|---|---|
| DC1441A | LTC3855EUJ Demo Board | Dual Output, VIN = 4.5V to 14V, VOUT1 = 1.8V @ 17A, VOUT2 = 1.2V @ 17A | $200.00 | |
| DC1586A | LTC3855EUJ Demo Board | Dual Output, VIN = 4.5V to 25V, VOUT1 = 3.3V @ 5A, VOUT2 = 2.5V @ 5A | $200.00 | |
| DC1617A-A | LTC3855EFE Demo Board | Dual Output VIN = 4.5V to 26V, VOUT1 = 2.5V @ 15A, VOUT2 = 1.8V @ 15A | $200.00 | |
| DC1617A-B | LTC3855EFE Demo Board | Dual Output VIN = 13V to 36V, VOUT1 = 12V @ 6A, VOUT2 = 5V @ 10A | $200.00 | |
| Buy Now | |||
Designed for Automotive and Transportation Applications
AEC-Q100 data is available for these specific part numbers. Please contact your local sales representative for more information regarding reliability reports or to inquire about parts that are not included. For more information, view our Automotive and Transportation page
| Part Number | Package | Temp | Price (1-99) |
Price (1k)* |
RoHS | |
|---|---|---|---|---|---|---|
| LTC3855IFE#PBF | TSSOP-38 | I | $5.54 | $3.88 | Yes | |
| LTC3855IFE#TRPBF | TSSOP-38 | I | $3.94 | Yes | ||
| LTC3855IUJ#PBF | 6x6 QFN-40 | I | $5.13 | $3.59 | Yes | |
| LTC3855IUJ#TRPBF | 6x6 QFN-40 | I | $3.65 | Yes | ||
| Buy Now • Request Samples | ||||||
Applications
- Computer Systems
- Telecom Systems
- Industrial and Medical Instruments
- DC Power Distribution Systems
People Who Viewed This Product Also Viewed
- LTC3880 - Dual Output PolyPhase Step-Down DC/DC Controller with Digital Power System Management
- LT8705 - 80V VIN and VOUT Synchronous 4-Switch Buck- Boost DC/DC Controller
- LTC3789 - High Efficiency, Synchronous, 4-Switch Buck-Boost Controller
- LT3080 - Adjustable 1.1A Single Resistor Low Dropout Regulator
- LTC3890 - 60V Low IQ, Dual, 2-Phase Synchronous Step-Down DC/DC Controller
- LTC4364 - Surge Stopper with Ideal Diode
- LT4363 - High Voltage Surge Stopper with Current Limit
- LT3758 - High Input Voltage, Boost, Flyback, SEPIC and Inverting Controller
- LTC3810 - 100V Current Mode Synchronous Switching Regulator Controller
- LT8610 - 42V, 2.5A Synchronous Step-Down Regulator with 2.5μA Quiescent Current
Product Notifications
Please login to your MyLinear account for notifications of datasheet updates, new document releases and LTspice model announcements for your favorite products. If you do not have a MyLinear account you may Sign Up Now.
Forgot your password? Click here.
Need help? Email mylinear@linear.com with questions and comments.
Design Tools
LTspice
LTspice® software is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. Click here to download LTspice
To launch a ready to run LTspice demonstration circuit for this part:
- Step 1: If you have not installed LTspice on this computer, download and install LTspice
- Step 2: Once LTspice is installed, click on the link(s) below to launch the simulation
- Step 3: If LTspice does not automatically open after clicking the link above, 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
To explore other ready to run LTspice demonstration circuits, please visit our Demo Circuits Collection.
Models for the following parts are available in LTspice:
LTC3855
LTpowerCAD
The LTpowerCAD design tool is a complete power supply design tool program that can significantly ease the tasks of power supply design. It guides users to a solution, selects power stage components, provides detailed power efficiency, shows quick loop bode plot stability and load transient analysis, and can export a final design to LTspice for simulation. Click here to download LTpowerCAD
To open the project file for this circuit:
- Step 1: If you have not installed LTpowerCAD on this computer, download and install LTpowerCAD
- Step 2: Once LTpowerCAD is installed, click on the link(s) below to open the project file
- LTC3855 Project - Dual, 2-Phase Synchronous Step-Down Controller with Inductor DCR Current Sensing (4.5-26V to 2.5V @ 15A & 1.8V @ 15A)
- LTC3855 Project - Dual, 2-Phase Synchronous Step-Down Controller with Rsense Current Sensing (13-36V to 12V @ 6A & 5V @ 10A)
- LTC3855 Project - Dual, 2-Phase Synchronous Step-Down Controller with Rsense Current Sensing (4.5-14V to 1.8V @ 17A & 1.2V @ 17A)
- LTC3855 Project - Dual, 2-Phase Synchronous Step-Down Controller with Inductor DCR Current Sensing (4.5-14V to 1.8V @ 17A & 1.2V @ 17A)
- LTC3855 Project - Dual, 2-Phase Synchronous Step-Down Controller with Rsense Current Sensing (4.5-26V to 2.5V @ 15A & 1.8V @ 15A)
- LTC3855 Project - Dual, 2-Phase Synchronous Step-Down Controller with Inductor DCR Current Sensing (13-36V to 12V @ 6A & 5V @ 10A)
- Step 3: If LTpowerCAD does not automatically open after clicking the link above, you can open the project file by right clicking on the link and selecting "Save Target As." After saving the file to your computer, start LTpowerCAD and open the project file by selecting 'Open Project' from the 'File' menu
Design tools for the following parts are available in LTpowerCAD:
LTC3855
LTC3855 Parallel
Technical Support
- For immediate technical assistance, contact your local sales office or distributor or call 1-800-4-LINEAR (US customers only) or 408-432-1900.
- For less urgent requests, please complete our Technical Support Request Form. Please allow 2-3 business days for reply.
