LTC3805 - Adjustable Frequency Current Mode Flyback DC/DC Controller

Features

  • VIN and VOUT Limited Only by External Components
  • Adjustable Slope Compensation
  • Adjustable Overcurrent Protection with Automatic Restart
  • Adjustable Operating Frequency (70kHz to 700kHz) with One External Resistor
  • Synchronizable to an External Clock
  • ±1.5% Reference Accuracy
  • Current Mode Operation for Excellent Line and Load Transient Response
  • RUN Pin with Precision Threshold and Adjustable Hysteresis
  • Programmable Soft-Start with One External Capacitor
  • Low Quiescent Current: 360μA
  • Small 10-Lead MSOP and 3mm × 3mm DFN
Designed for Automotive and Transportation Applications
AEC-Q100 generic family data available for specific packages


Typical Application

LTC3805 Typical Application
LTC3805 Typical Application

Description

The LTC3805 is a current mode controller for flyback DC/DC converters designed to drive an N-channel MOSFET in high input and output voltage converter applications. Operating frequency and slope compensation can be programmed by external resistors. Programmable overcurrent sensing protects the converter from short-circuits. Softstart can be programmed using an external capacitor and the soft-start capacitor also programs an automatic restart feature.

The LTC3805 provides ±1.5% output voltage accuracy and consumes only 360μA of quiescent current during normal operation and only 40μA during micropower startup. Using a 9.5V internal shunt regulator, the LTC3805 can be powered from a high VIN through a resistor or it can be powered directly from a low impedance DC voltage of 9V or less.

The LTC3805 is available in the 10-lead MSOP package and the 3mm × 3mm DFN package.

  Turn On Voltage
LTC3805 8.4V
LTC3805-5 4.5V

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
LTC3805EDD#PBF 3x3 DFN-10 DD E 05-08-1699 Yes
LTC3805EDD#TRPBF 3x3 DFN-10 DD E 05-08-1699 Yes
LTC3805EMSE#PBF MS-10E MSE E 05-08-1664 Yes
LTC3805EMSE#TRPBF MS-10E MSE E 05-08-1664 Yes
LTC3805HMSE#PBF MS-10E MSE H 05-08-1664 Yes
LTC3805HMSE#TRPBF MS-10E MSE H 05-08-1664 Yes
LTC3805IDD#PBF 3x3 DFN-10 DD I 05-08-1699 Yes
LTC3805IDD#TRPBF 3x3 DFN-10 DD I 05-08-1699 Yes
LTC3805IMSE#PBF MS-10E MSE I 05-08-1664 Yes
LTC3805IMSE#TRPBF MS-10E MSE I 05-08-1664 Yes
LTC3805MPMSE#PBF MS-10E MSE MP 05-08-1664 Yes
LTC3805MPMSE#TRPBF MS-10E MSE MP 05-08-1664 Yes


LTC3805 Package Drawing
LTC3805 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
LTC3805EDD#PBF 3x3 DFN-10 E $2.01 $1.39 Yes
LTC3805EDD#TRPBF 3x3 DFN-10 E $1.45 Yes
LTC3805EMSE#PBF MS-10E E $2.01 $1.39 Yes
LTC3805EMSE#TRPBF MS-10E E $1.45 Yes
LTC3805HMSE#PBF MS-10E H $2.51 $1.76 Yes
LTC3805HMSE#TRPBF MS-10E H $1.82 Yes
LTC3805IDD#PBF 3x3 DFN-10 I $2.10 $1.47 Yes
LTC3805IDD#TRPBF 3x3 DFN-10 I $1.53 Yes
LTC3805IMSE#PBF MS-10E I $2.10 $1.47 Yes
LTC3805IMSE#TRPBF MS-10E I $1.53 Yes
LTC3805MPMSE#PBF MS-10E MP $6.80 $4.76 Yes
LTC3805MPMSE#TRPBF MS-10E MP $4.82 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
DC1045A LTC3805EMSE Isolated Demo Board | 36V ≤ Vin ≤ 72V, Vout = 3.3V/3A $75.00
DC1311A-A LTC3805 Isolated Demo Board | Flyback Controller, 18V ≤ VIN ≤ 72V, Vout = 3.3V @ 3A $75.00
Buy Now
Click here to view our complete list of demo boards

Designed for Automotive and Transportation Applications

Please contact your local sales representative for more information regarding reliability reports and AEC-Q100 data 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
LTC3805HMSE#PBF MS-10E H $2.51 $1.76 Yes
LTC3805HMSE#TRPBF MS-10E H $1.82 Yes
LTC3805IMSE#PBF MS-10E I $2.10 $1.47 Yes
LTC3805IMSE#TRPBF MS-10E I $1.53 Yes
LTC3805MPMSE#PBF MS-10E MP $6.80 $4.76 Yes
LTC3805MPMSE#TRPBF MS-10E MP $4.82 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

  • Telecom Power Supplies
  • 42V and 12V Automotive Power Supplies
  • Isolated Electronic Equipment

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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:
LTC3805
LTC3805-5

Technical Support