LTC3851 - Synchronous Step-Down Switching Regulator Controller
Features
- Wide VIN Range: 4V to 38V Operation
- RSENSE 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 COUT
- Selectable Continuous, Pulse-Skipping or Burst Mode Operation at Light Loads
- Low Shutdown IQ: 20μA
- VOUT Range: 0.8V to 5.5V
- Thermally Enhanced 16-Lead MSOP, 16-Lead Narrow SSOP or 3mm × 3mm QFN Package
AEC-Q100 data available for specific packages
Typical Application
Description
The LTC3851 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 LTC3851 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 LTC3851-1 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 |
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 |
|---|---|---|---|---|---|
| LTC3851EGN#PBF | SSOP-16 | GN | E | 05-08-1641 (GN16) | Yes |
| LTC3851EGN#TRPBF | SSOP-16 | GN | E | 05-08-1641 (GN16) | Yes |
| LTC3851EMSE#PBF | MS-16E | MSE | E | 05-08-1667 | Yes |
| LTC3851EMSE#TRPBF | MS-16E | MSE | E | 05-08-1667 | Yes |
| LTC3851EUD#PBF | 3x3 QFN-16 | UD | E | 05-08-1691 | Yes |
| LTC3851EUD#TRPBF | 3x3 QFN-16 | UD | E | 05-08-1691 | Yes |
| LTC3851IGN#PBF | SSOP-16 | GN | I | 05-08-1641 (GN16) | Yes |
| LTC3851IGN#TRPBF | SSOP-16 | GN | I | 05-08-1641 (GN16) | Yes |
| LTC3851IMSE#PBF | MS-16E | MSE | I | 05-08-1667 | Yes |
| LTC3851IMSE#TRPBF | MS-16E | MSE | I | 05-08-1667 | Yes |
| LTC3851IUD#PBF | 3x3 QFN-16 | UD | I | 05-08-1691 | Yes |
| LTC3851IUD#TRPBF | 3x3 QFN-16 | UD | I | 05-08-1691 | 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 | |
|---|---|---|---|---|---|---|
| LTC3851EGN#PBF | SSOP-16 | E | $2.44 | $1.71 | Yes | |
| LTC3851EGN#TRPBF | SSOP-16 | E | $1.77 | Yes | ||
| LTC3851EMSE#PBF | MS-16E | E | $2.44 | $1.71 | Yes | |
| LTC3851EMSE#TRPBF | MS-16E | E | $1.77 | Yes | ||
| LTC3851EUD#PBF | 3x3 QFN-16 | E | $2.44 | $1.71 | Yes | |
| LTC3851EUD#TRPBF | 3x3 QFN-16 | E | $1.77 | Yes | ||
| LTC3851IGN#PBF | SSOP-16 | I | $2.77 | $1.94 | Yes | |
| LTC3851IGN#TRPBF | SSOP-16 | I | $2.00 | Yes | ||
| LTC3851IMSE#PBF | MS-16E | I | $2.77 | $1.94 | Yes | |
| LTC3851IMSE#TRPBF | MS-16E | I | $2.00 | Yes | ||
| LTC3851IUD#PBF | 3x3 QFN-16 | I | $2.77 | $1.94 | Yes | |
| LTC3851IUD#TRPBF | 3x3 QFN-16 | I | $2.00 | 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 |
|---|---|---|---|
| DC1171A-A | LTC3851EGN (Rsense) Demo Board | 4.5V < Vin < 14V, Vout: 1.5V/15A | $100.00 | |
| DC1171A-B | LTC3851EGN (DCR) Demo Board | 4.5V < Vin < 14V, Vout: 1.5V/15A | $100.00 | |
| 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 | |
|---|---|---|---|---|---|---|
| LTC3851IGN#PBF | SSOP-16 | I | $2.77 | $1.94 | Yes | |
| LTC3851IGN#TRPBF | SSOP-16 | I | $2.00 | Yes | ||
| LTC3851IMSE#PBF | MS-16E | I | $2.77 | $1.94 | Yes | |
| LTC3851IMSE#TRPBF | MS-16E | I | $2.00 | Yes | ||
| LTC3851IUD#PBF | 3x3 QFN-16 | I | $2.77 | $1.94 | Yes | |
| LTC3851IUD#TRPBF | 3x3 QFN-16 | I | $2.00 | Yes | ||
| Buy Now • Request Samples | ||||||
Applications
- Automotive Systems
- Telecom Systems
- Industrial Equipment
- Distributed DC Power Systems
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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
Models for the following parts are available in LTspice:
LTC3851
LTC3851-1
LTC3851A
LTC3851A-1
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
Design tools for the following parts are available in LTpowerCAD:
LTC3851A
LTC3851A-1
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.
