Features and Benefits
- Wide Input Range:
- Operation from 3.9V to 36V
- Overvoltage Lockout Protects Circuits Through 60V Transients
- 4A Maximum Output Current
- Integrated 30mΩ N-Channel Synchronous Switch
- Low Ripple (<15mVP-P) Burst Mode® Operation: IQ = 70µA at 12VIN to 3.3VOUT
- Programmable Input Undervoltage Lockout
- 0.8V Feedback Reference Voltage
- Output Voltage: 0.8V to 20V
- Programmable and Synchronizable Oscillator (170kHz to 1.5MHz)
- Soft-Startup and Output Voltage Tracking
- Short-Circuit Robust
- Power Good Flag
- Small Thermally Enhanced 4mm × 6mm QFN Package
The LT®3690 is an adjustable frequency monolithic buck switching regulator that accepts input voltages up to 36V. A high efficiency 90mΩ switch is included on the device along with the boost diode and the necessary oscillator, control, and logic circuitry. The internal synchronous power switch of 30mΩ increases efficiency and eliminates the need for an external Schottky catch diode. Current mode topology is used for fast transient response and good loop stability. Shutdown reduces input supply current to less than 1µA. The low ripple Burst Mode maintains high efficiency at low output currents while keeping output ripple below 15mV in typical applications.
The LT3690 features robust operation and is easily configurable. Using a resistor divider on the UVLO pin provides a programmable undervoltage lockout. A power good flag signals when VOUT reaches 90% of the programmed output voltage. Protection circuitry senses the current in the power switches to protect the LT3690 against short-circuit conditions. Frequency foldback and thermal shutdown provide additional protection. The LT3690 is available in a 4mm × 6mm QFN package with exposed pads for low thermal resistance.
- Automotive Systems
- Industrial Supplies
- Distributed Supply 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 1520A is a 36V, 4A synchronous Buck Regulator with 70μA Quiescent Current featuring the LT3690. The demo board is designed for 3.3V output from a 4.5V to 36V input with transient up to 60V. The wide input range of the LT3690 allows a variety of input sources, such as automotive batteries and industrial supplies. The switching frequency can be programmed either via oscillator resistor or external clock over a 170kHz to 1.5MHz 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:
Product Selection Guide (1)
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.