Features and Benefits
- 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
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.
- DSL and Cable Modems
- Distributed Power Regulation
- Wall Transformer Regulation
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (1)
Demonstration circuit 1541A-A is an adjustable output voltage, 2.6A output current Monolithic Buck Regulator with dual LDO regulators featuring the LT3694. The buck regulator is capable of generating up to 2.6A at its output and the two LDO regulators (which are powered from the buck output) are capable of providing 450mA each. The demo board has a 4.5V to 36V input range (70V transients) and provides three outputs: 3.3V at 1.7A, 2.5V at 450mA and 1.8V at 450mA.
The LT3694 can be synchronized to an external clock with the SYNC pin. The LT3694-1 offers a CLKOUT pin allowing other DC/DC converters to synchronize to the LT3694-1 clock.
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
To launch ready-to-run LTspice demonstration circuits for this part:
Step 1: Download and install LTspice on your computer.
Step 2: Click on the link in the section below to download a demonstration circuit.
Step 3: If LTspice does not automatically open after clicking the link below, 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.
Models for the following parts are available in LTspice:
LTpowerCAD® is a power supply design program which selects power stage components, provides detailed power efficiency, shows quick loop Bode plot stability and load transient analysis, and can export to LTspice for simulation.
Design tools for the following parts are available in LTpowerCAD:
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
Sample & Buy
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 Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.