High Voltage Synchronous Current Mode Step-Down Controller with Adjustable Operating Frequency
Features and Benefits
- High Voltage Operation: Up to 60V
- Synchronizable Up to 600kHz
- Adjustable Constant Frequency: 100kHz to 500kHz
- Output Voltages Up to 36V
- Adaptive Nonoverlap Circuitry Prevents Switch Shoot-Through
- Reverse Inductor Current Inhibit for Discontinuous Operation Improves Efficiency with Light Loads
- Programmable Soft-Start
- 120μA No Load Quiescent Current
- 10μA Shutdown Supply Current
- 1% Regulation Accuracy
- Standard Gate N-Channel Power MOSFETs
- Current Limit Unaffected by Duty Cycle
- Reverse Overcurrent Protection
- 16-Lead Thermally Enhanced TSSOP Package, 16-Pin PDIP
The LT3845 is a high voltage, synchronous, current mode controller used for medium to high power, high efficiency supplies. It offers a wide 4V to 60V input range (7.5V minimum start-up voltage). An on-board regulator simplifies the biasing requirements by providing IC power directly from VIN.
Burst Mode® operation maintains high efficiency at light loads by reducing IC quiescent current to 120μA. Light load efficiency is also improved with the reverse inductor current inhibit function which supports discontinuous operation.
Additional features include adjustable fixed operating frequency that can be synchronized to an external clock for noise sensitive applications, gate drivers capable of driving large N-channel MOSFETs, a precision undervoltage lockout, 10μA shutdown current, short-circuit protection and a programmable soft-start.
The LT3845 is available in a 16-lead thermally enhanced TSSOP package and 16-pin through hole N package.
|LT3845A||Improved Performance In Over Current Conditions|
- 12V and 42V Automotive and Heavy Equipment
- 48V Telecom Power Supplies
- Avionics and Industrial Control Systems
- Distributed Power Converters
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 1073 is a 100kHz-500kHz programmable frequency, high voltage, current-mode DC/DC step-down converter featuring the LT3845. The operating frequency can be synchronized up to 600kHz. The demo board is designed for 12V @ 6.25A (75W) output from a 20V to 55V input. A soft-start feature controls the output voltage slew rate at start-up, reducing current surges and voltage overshoots. The modes of operation (Burst Mode, Discontinuous Current Mode and Continuous Current Mode) are jumper selectable. Both Burst Mode and Discontinuous Current Mode increase the efficiency at light loads. Continuous Current Mode will maintain a constant switching frequency regardless of the load 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.
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.