LT3645 - 36V 500mA Step-Down Regulator and 200mA LDO
Features
- Wide Input Range:
Operation from 3.6V to 36V
Overvoltage Lockout Protects Circuit Through 55V Transients on Input - 500mA Output Current Switching Regulator
- High Switching Frequency: 750kHz
- 200mA Low Dropout Linear Regulator
1.2V to 16V Input; 0.8V to 8V Output
310mV Dropout Voltage VCC2 to OUT2 - Precision Programmable Undervoltage Lockout
- Short-Circuit Robust
- Internal Soft-Start
- <2μA Shutdown Current
- Small Thermally Enhanced 16-Lead (3mm × 3mm) QFN and 12-Lead MSE Packages
AEC-Q100 data available for specific packages
Typical Application
Description
The LT®3645 is a dual output regulator combining a 500mA buck regulator and a 200mA low dropout linear regulator (LDO). The wide input voltage range of 3.6V to 36V makes the LT3645 suitable for regulating power from a wide variety of sources, including 24V industrial supplies and automotive batteries. Its high operating frequency allows the use of tiny, low cost inductors and capacitors, resulting in a very small solution.
Cycle-by-cycle current limit and frequency foldback provide protection against shorted outputs. Soft-start and frequency foldback eliminate input current surge during start-up.
The linear regulator operates from the VCC2 pin at voltages down to 1.2V. It supplies 200mA of output current with a typical dropout voltage of 310mV.
Other features of the LT3645 include a <2μA shutdown, short circuit protection, soft-start and thermal shutdown. The LT3645 is available in the thermally enhanced 16-lead (3mm × 3mm) QFN package, or a 12-lead MSE package.
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 |
|---|---|---|---|---|---|
| LT3645EMSE#PBF | MS-12E | MSE | E | 05-08-1666 | Yes |
| LT3645EMSE#TRPBF | MS-12E | MSE | E | 05-08-1666 | Yes |
| LT3645EUD#PBF | 3x3 QFN-16 | UD | E | 05-08-1691 | Yes |
| LT3645EUD#TRPBF | 3x3 QFN-16 | UD | E | 05-08-1691 | Yes |
| LT3645HMSE#PBF | MS-12E | MSE | H | 05-08-1666 | Yes |
| LT3645HMSE#TRPBF | MS-12E | MSE | H | 05-08-1666 | Yes |
| LT3645IMSE#PBF | MS-12E | MSE | I | 05-08-1666 | Yes |
| LT3645IMSE#TRPBF | MS-12E | MSE | I | 05-08-1666 | Yes |
| LT3645IUD#PBF | 3x3 QFN-16 | UD | I | 05-08-1691 | Yes |
| LT3645IUD#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 | |
|---|---|---|---|---|---|---|
| LT3645EMSE#PBF | MS-12E | E | $3.36 | $2.35 | Yes | |
| LT3645EMSE#TRPBF | MS-12E | E | $2.41 | Yes | ||
| LT3645EUD#PBF | 3x3 QFN-16 | E | $3.22 | $2.25 | Yes | |
| LT3645EUD#TRPBF | 3x3 QFN-16 | E | $2.31 | Yes | ||
| LT3645HMSE#PBF | MS-12E | H | $4.06 | $2.84 | Yes | |
| LT3645HMSE#TRPBF | MS-12E | H | $2.90 | Yes | ||
| LT3645IMSE#PBF | MS-12E | I | $3.70 | $2.59 | Yes | |
| LT3645IMSE#TRPBF | MS-12E | I | $2.65 | Yes | ||
| LT3645IUD#PBF | 3x3 QFN-16 | I | $3.54 | $2.48 | Yes | |
| LT3645IUD#TRPBF | 3x3 QFN-16 | I | $2.54 | 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 |
|---|---|---|---|
| DC1428A | LT3645EMSE Demo Board | VIN = 5V to 36V, VOUT1 = 3.3V @ 300mA, VOUT2= 2.5V @ 200mA | $125.00 | |
| 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 | |
|---|---|---|---|---|---|---|
| LT3645HMSE#PBF | MS-12E | H | $4.06 | $2.84 | Yes | |
| LT3645HMSE#TRPBF | MS-12E | H | $2.90 | Yes | ||
| LT3645IMSE#PBF | MS-12E | I | $3.70 | $2.59 | Yes | |
| LT3645IMSE#TRPBF | MS-12E | I | $2.65 | Yes | ||
| Buy Now • Request Samples | ||||||
Applications
- Automotive CMOS Image Sensors
- Industrial/Automotive Micro-Controller Supply
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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:
LT3645
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:
LT3645
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.
