LTC3850 - Dual, 2-Phase Synchronous Step-Down Switching Controller

Features

  • Dual, 180° Phased Controllers Reduce Required
  • Input Capacitance and Power Supply Induced Noise
  • High Efficiency: Up to 95%
  • RSENSE 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 VIN Range: 4V to 24V (30V for LTC3850I) Operation
  • Adjustable Soft-Start Current Ramping or Tracking
  • Foldback Output Current Limiting
  • Output Overvoltage Protection
  • Power Good Output Voltage Monitor
  • 28-Pin 4mm × 4mm, 4mm × 5mm QFN and Narrow SSOP Packages
Designed for Automotive and Transportation Applications
AEC-Q100 data available for specific packages


Typical Application

LTC3850 Typical Application
LTC3850 Typical Application

Description

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 x 4mm, 4mm x 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

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
LTC3850EGN-1#PBF SSOP-28 GN E 05-08-1641 (GN28) Yes
LTC3850EGN-1#TRPBF SSOP-28 GN E 05-08-1641 (GN28) Yes
LTC3850EGN#PBF SSOP-28 GN E 05-08-1641 (GN28) Yes
LTC3850EGN#TRPBF SSOP-28 GN E 05-08-1641 (GN28) Yes
LTC3850EUF#PBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3850EUF#TRPBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3850EUFD#PBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3850EUFD#TRPBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3850IGN-1#PBF SSOP-28 GN I 05-08-1641 (GN28) Yes
LTC3850IGN-1#TRPBF SSOP-28 GN I 05-08-1641 (GN28) Yes
LTC3850IGN#PBF SSOP-28 GN I 05-08-1641 (GN28) Yes
LTC3850IGN#TRPBF SSOP-28 GN I 05-08-1641 (GN28) Yes
LTC3850IUF#PBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LTC3850IUF#TRPBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LTC3850IUFD#PBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LTC3850IUFD#TRPBF 4x5 QFN-28 UFD I 05-08-1712 Yes


LTC3850 Package Drawing
LTC3850 Package Drawing
LTC3850 Package Drawing

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
LTC3850EGN-1#PBF SSOP-28 E $3.43 $2.40 Yes
LTC3850EGN-1#TRPBF SSOP-28 E $2.46 Yes
LTC3850EGN#PBF SSOP-28 E $3.43 $2.40 Yes
LTC3850EGN#TRPBF SSOP-28 E $2.46 Yes
LTC3850EUF#PBF 4x5 QFN-28 E $3.43 $2.40 Yes
LTC3850EUF#TRPBF 4x5 QFN-28 E $2.46 Yes
LTC3850EUFD#PBF 4x5 QFN-28 E $3.43 $2.40 Yes
LTC3850EUFD#TRPBF 4x5 QFN-28 E $2.46 Yes
LTC3850IGN-1#PBF SSOP-28 I $3.64 $2.55 Yes
LTC3850IGN-1#TRPBF SSOP-28 I $2.61 Yes
LTC3850IGN#PBF SSOP-28 I $3.64 $2.55 Yes
LTC3850IGN#TRPBF SSOP-28 I $2.61 Yes
LTC3850IUF#PBF 4x5 QFN-28 I $3.64 $2.55 Yes
LTC3850IUF#TRPBF 4x5 QFN-28 I $2.61 Yes
LTC3850IUFD#PBF 4x5 QFN-28 I $3.64 $2.55 Yes
LTC3850IUFD#TRPBF 4x5 QFN-28 I $2.61 Yes
Buy NowRequest Samples
* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.

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
DC1126A LTC3850EUF Demo Board | 6.5V ≤ Vin ≤ 14V, Vout = 3.3V@5A & 2.5V@5A $150.00
DC1185A-A LTC3850EUF Demo Board | 4.5V ≤ VIN ≤ 14V; VOUT1: 2V @ 10A, VOUT2: 1.8V @ 10A $150.00
DC1185B-A LTC3850EUF Demo Board | 4.5V ≤ VIN ≤ 14V; VOUT1: 2V @ 10A, VOUT2: 1.8V @ 10A $150.00
DC1185B-B LTC3850EUF Demo Board | 4.5V ≤ VIN ≤ 14V; VOUT1: 1.5V @ 15A, VOUT2: 1.2V @ 15A $150.00
DC1231A-A LTC3850EGN Demo Board | 6.5V < Vin < 24V, Vout 1=3.3V/5A, Vout 2=2.5V/5A $150.00
DC1231A-B LTC3850EGN Demo Board | 6.5V < Vin < 24V, Vout 1=3.3V/5A, Vout 2=2.5V/5A, with DCR Current Sense $150.00
Buy Now
Click here to view our complete list of demo boards

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
LTC3850IGN-1#PBF SSOP-28 I $3.64 $2.55 Yes
LTC3850IGN-1#TRPBF SSOP-28 I $2.61 Yes
LTC3850IGN#PBF SSOP-28 I $3.64 $2.55 Yes
LTC3850IGN#TRPBF SSOP-28 I $2.61 Yes
LTC3850IUF#PBF 4x5 QFN-28 I $3.64 $2.55 Yes
LTC3850IUF#TRPBF 4x5 QFN-28 I $2.61 Yes
LTC3850IUFD#PBF 4x5 QFN-28 I $3.64 $2.55 Yes
LTC3850IUFD#TRPBF 4x5 QFN-28 I $2.61 Yes
Buy NowRequest Samples
* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.

Applications

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

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:
LTC3850
LTC3850-1
LTC3850-2

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:

Design tools for the following parts are available in LTpowerCAD:
LTC3850
LTC3850 Parallel

Technical Support