Features and Benefits
- Wide Input Range:
- Operation From 3.6V to 36V
- Overvoltage Lockout Protects Circuit through
- 60V Transients
- 2A Maximum Output Current
- Adjustable Switching Frequency: 200kHz to 2.4MHz
- Low Shutdown Current: IQ < 1µA
- Integrated Boost Diode
- Synchronizable Between 250kHz to 2MHz
- Power Good Flag
- Saturating Switch Design: 0.25Ω On-Resistance
- 0.790V Feedback Reference Voltage
- Output Voltage: 0.79V to 20V
- Soft-Start Capability
- Small 10-Pin Thermally Enhanced MSOP and (3mm x 3mm) DFN Packages
The LT3685 is an adjustable frequency (200kHz to 2.4MHz) monolithic step-down switching regulator that accepts input voltages up to 38V operating and 60V maximum. An internal overvoltage protection circuit turns off the power switch when VIN is above 38V typical (36V minimum) which then allows the part to safely withstand 60V transients. A high efficiency 0.25Ω switch is included on the die along with a boost Schottky diode and the necessary oscillator, control, and logic circuitry. Current mode topology is used for fast transient response and good loop stability. The LT3685’s high operating frequency allows the use of small, low cost inductors and ceramic capacitors resulting in low output ripple while keeping total solution size to a minimum. The low current shutdown mode reduces input supply current to less than 1μA while a resistor and capacitor on the RUN/SS pin provide a controlled output voltage ramp (soft-start). A power good ﬂag signals when VOUT reaches 89% of the programmed output voltage. The LT3685 is available in 10-Pin MSOP and 3mm × 3mm DFN packages with exposed pads for low thermal resistance.
- Automotive Battery Regulation
- Set Top Box
- Distributed Supply Regulation
- Industrial Supplies
- 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 (2)
Demonstration circuit 1212A-B is a monolithic step-dwon DC/DC switching regulatro featuring the LT3685 in the 3x3 DFN-10 package. The demo board provides 5V@2A from a 6.3V to 38V input and has transient protection up to 60V. The demo boards default switching frequency is 800kHz, but the LT3685 has a SYNC pin which allows frequency synchronization to an external clock over a 250kHz to 2MHz range. The LT3685's quiescent current is 0.9mA, while the LT3480 has a 70uA quiescent current.
An EMC filter at the input makes the circuit compatible with EMC standard EN55022 Class B.
Demonstration circuit 1167 is a monolithic step-down DC/DC switching regulator featuring the LT3685 in the MSOP-10 exposed pad package. The demo board provides 5V @ 2A from a 6.3V to 38V input and has transient protection up to 60V. The demo boards default switching frequency is 500kHz, but the LT3685 has a SYNC pin which allows frequency synchronization to an external clock over a 250kHz to 2MHz range.
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.