Features and Benefits
- Wide Input Range:
- Operation from 3.8V to 36V
- Low Ripple (<25mVP-P ) Burst Mode Operation:
- IQ = 115μA at 12VIN to 3.3V and 5V
- Programmable, Defeatable Window Watchdog Timer
- Two Independently Programmable Power-On-Reset Timers
- Synchronizable, Adjustable 350kHz-2.2MHz Switching Frequency
- Two 800mA Output Switching Regulators with Internal Power Switches
- Programmable Input Undervoltage Lockout with Hysteresis
- Thermally Enhanced 24-Pin TSSOP and 4mm × 4mm QFN Packages
The LT3688 is an adjustable frequency (350kHz to 2.2MHz) dual monolithic step-down switching regulator with two power-on reset timers and a watchdog timer. The regulator operates off inputs up to 36V. Low ripple Burst Mode® operation maintains high efficiency at low output current while keeping output ripple below 25mV in a typical application, with input quiescent current of just 115μA. Shutdown circuitry reduces input supply current to less than 1μA while EN/UVLO is pulled low.
The reset and watchdog timeout periods are both adjustable using external capacitors. Tight accuracy specifications and glitch immunity ensure reliable reset operation without false triggering. The open collector RST pins will pull down if the monitored output voltage drops 10% below the programmed value. The LT3688 watchdog timer monitors for watchdog falling edges grouped too close together or too far apart.
The LT3688 is available in 24-Pin TSSOP and 4mm × 4mm QFN packages, each with an exposed pad for low thermal resistance.
- Automotive Electronic Control Units
- Industrial Power Supplies
- High-Reliability μProcessor Systems
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 1439A is an adjustable dual monolithic step-down switching regulator with two adjustable power-on reset timers and an adjustable watchdog timer. The regulator operates off inputs up to 36V and withstands transients up to 60V. The two buck outputs are capable of generating up to 800mA each and both of them have independent RUN/SS function.
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:
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
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Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.