LT3694 - 36V, 2.6A Monolithic Buck Regulator With Dual LDO
Features
- Wide Input Range: 4V to 36V
- Overvoltage Shutdown Protects Circuit Through 70V Transients
- 2.6A Output Switching Regulator with Internal Power Switch
- Dual, Low Dropout, Linear Regulator Controllers with Programmable Current Limit
- Tracking/Soft-Start Inputs and Power Good Output Simplify Soft-Start and Supply Sequencing
- Uses Small Inductors and Ceramic Capacitors
- VOUT(MIN) = 0.75V (Buck and LDOs)
- Adjustable 250kHz to 2.5MHz Switching Frequency
- Accurate Enable Threshold Allows User Programmable Undervoltage Lockout
- Options for Clock Synchronization (LT3694) or Clock Output to Enable Synchronization to Other Switching Regulators (LT3694-1)
- Thermally Enhanced 28-Lead 4mm × 5mm QFN and 20-Lead TSSOP Packages
AEC-Q100 data available for specific packages
Typical Application
Description
The LT3694/LT3694-1 are monolithic, current mode DC/DC converters with dual, low dropout regulator controllers. The switching converter is a step-down converter capable of generating up to 2.6A at its output. Each regulator has independent track/soft-start circuits simplifying power supply sequencing and interfacing with microcontrollers and DSPs.
The switching frequency is set with a single resistor with a range of 250kHz to 2.5MHz. The high switching frequency permits the use of small inductors and ceramic capacitors leading to very small triple output solutions. The constant switching frequency, combined with low impedance ceramic capacitors, results in low, predictable output ripple. Protection circuitry senses the current in the power switch and external Schottky catch diode to protect the LT3694 against short-circuit conditions. Frequency foldback and thermal shutdown provide additional protection.
With its wide input voltage range of 4V to 36V, the LT3694 regulates a broad array of power sources from 4-cell batteries and 5V logic rails to unregulated wall transformers, lead acid batteries and distributed power supplies. The LT3694 can be synchronized to an external clock with the SYNC pin while the LT3694-1 offers a CLKOUT pin allowing other DC/DC converters to synchronize to the LT3694-1 clock.
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 |
|---|---|---|---|---|---|
| LT3694EFE-1#PBF | TSSOP-20 | FE | E | 05-08-1663 (CB) | Yes |
| LT3694EFE-1#TRPBF | TSSOP-20 | FE | E | 05-08-1663 (CB) | Yes |
| LT3694EFE#PBF | TSSOP-20 | FE | E | 05-08-1663 (CB) | Yes |
| LT3694EFE#TRPBF | TSSOP-20 | FE | E | 05-08-1663 (CB) | Yes |
| LT3694EUFD-1#PBF | 4x5 QFN-28 | UFD | E | 05-08-1712 | Yes |
| LT3694EUFD-1#TRPBF | 4x5 QFN-28 | UFD | E | 05-08-1712 | Yes |
| LT3694EUFD#PBF | 4x5 QFN-28 | UFD | E | 05-08-1712 | Yes |
| LT3694EUFD#TRPBF | 4x5 QFN-28 | UFD | E | 05-08-1712 | Yes |
| LT3694IFE-1#PBF | TSSOP-20 | FE | I | 05-08-1663 (CB) | Yes |
| LT3694IFE-1#TRPBF | TSSOP-20 | FE | I | 05-08-1663 (CB) | Yes |
| LT3694IFE#PBF | TSSOP-20 | FE | I | 05-08-1663 (CB) | Yes |
| LT3694IFE#TRPBF | TSSOP-20 | FE | I | 05-08-1663 (CB) | Yes |
| LT3694IUFD-1#PBF | 4x5 QFN-28 | UFD | I | 05-08-1712 | Yes |
| LT3694IUFD-1#TRPBF | 4x5 QFN-28 | UFD | I | 05-08-1712 | Yes |
| LT3694IUFD#PBF | 4x5 QFN-28 | UFD | I | 05-08-1712 | Yes |
| LT3694IUFD#TRPBF | 4x5 QFN-28 | UFD | I | 05-08-1712 | 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 | |
|---|---|---|---|---|---|---|
| LT3694EFE-1#PBF | TSSOP-20 | E | $5.71 | $4.00 | Yes | |
| LT3694EFE-1#TRPBF | TSSOP-20 | E | $4.06 | Yes | ||
| LT3694EFE#PBF | TSSOP-20 | E | $5.71 | $4.00 | Yes | |
| LT3694EFE#TRPBF | TSSOP-20 | E | $4.06 | Yes | ||
| LT3694EUFD-1#PBF | 4x5 QFN-28 | E | $5.50 | $3.85 | Yes | |
| LT3694EUFD-1#TRPBF | 4x5 QFN-28 | E | $3.91 | Yes | ||
| LT3694EUFD#PBF | 4x5 QFN-28 | E | $5.50 | $3.85 | Yes | |
| LT3694EUFD#TRPBF | 4x5 QFN-28 | E | $3.91 | Yes | ||
| LT3694IFE-1#PBF | TSSOP-20 | I | $6.29 | $4.40 | Yes | |
| LT3694IFE-1#TRPBF | TSSOP-20 | I | $4.46 | Yes | ||
| LT3694IFE#PBF | TSSOP-20 | I | $6.29 | $4.40 | Yes | |
| LT3694IFE#TRPBF | TSSOP-20 | I | $4.46 | Yes | ||
| LT3694IUFD-1#PBF | 4x5 QFN-28 | I | $6.06 | $4.24 | Yes | |
| LT3694IUFD-1#TRPBF | 4x5 QFN-28 | I | $4.30 | Yes | ||
| LT3694IUFD#PBF | 4x5 QFN-28 | I | $6.06 | $4.24 | Yes | |
| LT3694IUFD#TRPBF | 4x5 QFN-28 | I | $4.30 | 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 |
|---|---|---|---|
| DC1541A-A | LT3694EFE Demo Board | Triple Output, 4.5V ≤ VIN ≤ 36V (70V Transients), VOUT1 = 3.3V@1.7A (Buck), VOUT2 = 2.5V@450mA (LDO), VOUT3=1.8V@450mA(LDO) | $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 | |
|---|---|---|---|---|---|---|
| LT3694IFE-1#PBF | TSSOP-20 | I | $6.29 | $4.40 | Yes | |
| LT3694IFE-1#TRPBF | TSSOP-20 | I | $4.46 | Yes | ||
| LT3694IFE#PBF | TSSOP-20 | I | $6.29 | $4.40 | Yes | |
| LT3694IFE#TRPBF | TSSOP-20 | I | $4.46 | Yes | ||
| Buy Now • Request Samples | ||||||
Applications
- Automotive
- Industrial
- DSL and Cable Modems
- Distributed Power Regulation
- Wall Transformer Regulation
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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:
LT3694
LT3694-1
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:
LT3694
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.
