Product Details

One very important, but not the much known future of LTC3649 is ability provide hold-up time for critical systems at power outage. Usual solution for providing energy during hold-up time is to use dedicated controllers and storage capacitors. Such approach is absolutely adequate if high levels of energy needed during the power interruption. However, if this is not a need and hold-up time is relatively short, then LTC3649 can be used. Converter based on this IC works as ‘conventional’ voltage source, at normal operation conditions. However, it changes to energy source to provide hold-up time during the power interruption. Correspondingly, in normal operation conditions LTC3649 works as step-down converter, however, it turns to step-up converter when input voltage disconnected. LTC3649 keeps programmed value of input voltage on the terminals of the critical loads by discharging its own output capacitor.


LTC3649 Hold-Up Circuit Using a Buck Regulator with Vin Boost Capabilities

LTC3649 Hold-Up Circuit Using a Buck Regulator with VIN Boost Capabilities


LTC3649 Hold Up Waveforms

LTC3649 Hold-Up Circuit Waveforms


The LTC3649 is a high efficiency 60V, 4A synchronous monolithic step-down regulator. The regulator features a single resistor programmable output voltage, internal compensation and high efficiencies over a wide VOUT range. The step-down regulator operates from an input voltage range of 3.1V to 60V and provides an adjustable rail-to-rail output range from (VIN – 0.5V) to ground while delivering up to 4A of output current.

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.