LT3689/LT3689-5 - 700mA Step-Down Regulator with Power-On Reset and Watchdog Timer
Features
- Wide Input Range: Operation from 3.6V to 36V
- 85μA IQ at 12VIN to 3.3VOUT
- Low Ripple Burst Mode® Operation Allows Output Ripple <15mVP-P
- Programmable, Defeatable Watchdog Timer with Window or Timeout Control
- Programmable Power-On Reset Timer (POR)
- Synchronizable, Adjustable 350kHz to 2.2MHz Switching Frequency
- 700mA Output Switching Regulator with Internal Power Switch
- Fixed 5V or Adjustable Output Voltage
- 800mV Feedback Voltage
- Programmable Input Undervoltage Lockout with Hysteresis
- 16-Pin 3mm × 3mm QFN and 16-Pin MSOP Packages
Overvoltage Lockout Protects Circuits through 60V Transients
AEC-Q100 data available for specific packages
Typical Application
Description
The LT3689 is an adjustable frequency (350kHz to 2.2MHz) monolithic step-down switching regulator with a power-on reset and watchdog timer. The regulator operates from inputs up to 36V and withstands transients up to 60V. Low ripple Burst Mode® operation maintains high efficiency at low output current while keeping output ripple below 15mV in a typical application, with input quiescent current of just 85μA. Shutdown circuitry reduces input supply current to less than 1μA while EN/UVLO is pulled low. Using a resistor divider on the EN/UVLO pin provides a programmable undervoltage lockout. Current limit, frequency foldback and thermal shutdown provide fault protection.
The reset and watchdog timeout periods are independently adjustable using external capacitors. Tight accuracy specifications and glitch immunity ensure reliable reset operation of a system without false triggering. The open collector RST will pull down if output voltage drops 10% below the programmed value. The watchdog timer is pin-selectable for window or timeout modes. In timeout mode, WDO pulls low if too long of a period passes before a watchdog transition is detected. In window mode, the LT3689 monitors for WDI falling edges grouped too close together or too far apart.
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 |
|---|---|---|---|---|---|
| LT3689EMSE-5#PBF | MS-16E | MSE | E | 05-08-1667 | Yes |
| LT3689EMSE-5#TRPBF | MS-16E | MSE | E | 05-08-1667 | Yes |
| LT3689EMSE#PBF | MS-16E | MSE | E | 05-08-1667 | Yes |
| LT3689EMSE#TRPBF | MS-16E | MSE | E | 05-08-1667 | Yes |
| LT3689EUD-5#PBF | 3x3 QFN-16 | UD | E | 05-08-1691 | Yes |
| LT3689EUD-5#TRPBF | 3x3 QFN-16 | UD | E | 05-08-1691 | Yes |
| LT3689EUD#PBF | 3x3 QFN-16 | UD | E | 05-08-1691 | Yes |
| LT3689EUD#TRPBF | 3x3 QFN-16 | UD | E | 05-08-1691 | Yes |
| LT3689HMSE-5#PBF | MS-16E | MSE | H | 05-08-1667 | Yes |
| LT3689HMSE-5#TRPBF | MS-16E | MSE | H | 05-08-1667 | Yes |
| LT3689HMSE#PBF | MS-16E | MSE | H | 05-08-1667 | Yes |
| LT3689HMSE#TRPBF | MS-16E | MSE | H | 05-08-1667 | Yes |
| LT3689IMSE-5#PBF | MS-16E | MSE | I | 05-08-1667 | Yes |
| LT3689IMSE-5#TRPBF | MS-16E | MSE | I | 05-08-1667 | Yes |
| LT3689IMSE#PBF | MS-16E | MSE | I | 05-08-1667 | Yes |
| LT3689IMSE#TRPBF | MS-16E | MSE | I | 05-08-1667 | Yes |
| LT3689IUD-5#PBF | 3x3 QFN-16 | UD | I | 05-08-1691 | Yes |
| LT3689IUD-5#TRPBF | 3x3 QFN-16 | UD | I | 05-08-1691 | Yes |
| LT3689IUD#PBF | 3x3 QFN-16 | UD | I | 05-08-1691 | Yes |
| LT3689IUD#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 | |
|---|---|---|---|---|---|---|
| LT3689EMSE-5#PBF | MS-16E | E | $4.64 | $3.25 | Yes | |
| LT3689EMSE-5#TRPBF | MS-16E | E | $3.31 | Yes | ||
| LT3689EMSE#PBF | MS-16E | E | $4.64 | $3.25 | Yes | |
| LT3689EMSE#TRPBF | MS-16E | E | $3.31 | Yes | ||
| LT3689EUD-5#PBF | 3x3 QFN-16 | E | $4.57 | $3.20 | Yes | |
| LT3689EUD-5#TRPBF | 3x3 QFN-16 | E | $3.26 | Yes | ||
| LT3689EUD#PBF | 3x3 QFN-16 | E | $4.57 | $3.20 | Yes | |
| LT3689EUD#TRPBF | 3x3 QFN-16 | E | $3.26 | Yes | ||
| LT3689HMSE-5#PBF | MS-16E | H | $5.51 | $3.86 | Yes | |
| LT3689HMSE-5#TRPBF | MS-16E | H | $3.92 | Yes | ||
| LT3689HMSE#PBF | MS-16E | H | $5.51 | $3.86 | Yes | |
| LT3689HMSE#TRPBF | MS-16E | H | $3.92 | Yes | ||
| LT3689IMSE-5#PBF | MS-16E | I | $5.16 | $3.61 | Yes | |
| LT3689IMSE-5#TRPBF | MS-16E | I | $3.67 | Yes | ||
| LT3689IMSE#PBF | MS-16E | I | $5.16 | $3.61 | Yes | |
| LT3689IMSE#TRPBF | MS-16E | I | $3.67 | Yes | ||
| LT3689IUD-5#PBF | 3x3 QFN-16 | I | $5.09 | $3.56 | Yes | |
| LT3689IUD-5#TRPBF | 3x3 QFN-16 | I | $3.62 | Yes | ||
| LT3689IUD#PBF | 3x3 QFN-16 | I | $5.09 | $3.56 | Yes | |
| LT3689IUD#TRPBF | 3x3 QFN-16 | I | $3.62 | 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 |
|---|---|---|---|
| DC1312A | LT3689EUD Demo Board | 4.5V ≤ VIN ≤ 36V (60V Transients), VOUT = 3.3V @ 700mA, | Contact Factory | |
| 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 | |
|---|---|---|---|---|---|---|
| LT3689HMSE-5#PBF | MS-16E | H | $5.51 | $3.86 | Yes | |
| LT3689HMSE-5#TRPBF | MS-16E | H | $3.92 | Yes | ||
| LT3689HMSE#PBF | MS-16E | H | $5.51 | $3.86 | Yes | |
| LT3689HMSE#TRPBF | MS-16E | H | $3.92 | Yes | ||
| LT3689IMSE-5#PBF | MS-16E | I | $5.16 | $3.61 | Yes | |
| LT3689IMSE-5#TRPBF | MS-16E | I | $3.67 | Yes | ||
| LT3689IMSE#PBF | MS-16E | I | $5.16 | $3.61 | Yes | |
| LT3689IMSE#TRPBF | MS-16E | I | $3.67 | Yes | ||
| LT3689IUD-5#PBF | 3x3 QFN-16 | I | $5.09 | $3.56 | Yes | |
| LT3689IUD-5#TRPBF | 3x3 QFN-16 | I | $3.62 | Yes | ||
| LT3689IUD#PBF | 3x3 QFN-16 | I | $5.09 | $3.56 | Yes | |
| LT3689IUD#TRPBF | 3x3 QFN-16 | I | $3.62 | Yes | ||
| Buy Now • Request Samples | ||||||
Applications
- Automotive Electronic Control Units
- Industrial Power Supplies
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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
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Models for the following parts are available in LTspice:
LT3689
LT3689-5
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.
