Features and Benefits
- Pin Compatible with LTC3310/LTC3310S and LTC3311
- Silent Switcher®2 Architecture:
Ultralow EMI Emissions
- High Efficiency—4.5mΩ NMOS & 16mΩ PMOS
- Wide Bandwidth, Fast Transient Response
- Safely Tolerates Inductor Saturation in Overload
- VIN Range: 2.25V to 5.5V
- VOUT Range: 0.5V to VIN
- VOUT Accuracy: ±1% with Remote Sense
- Peak Current Mode Control
- Minimum On-Time: 35ns
- Programmable Frequency to 5MHz
- Shutdown Current: 1μA
- Precision 400mV Enable Threshold, 1μA in Shutdown
- Output Soft-Start with Voltage Tracking
- Power Good Output
- Die Temperature Monitor
- Configurable for Paralleling Power Stages in Forced Continuous Mode
- Thermally-Enhanced 3mm × 3mm LQFN Package
- AEC-Q100 Qualified for Automotive Applications
The LTC3311S is a very small, low noise, monolithic step-down DC/DC converter capable of providing up to 12.5A of output current from a 2.25V to 5.5V input supply. The device employs Silent Switcher 2 architecture with internal hot loop bypass capacitors to achieve both low EMI and high efficiency at switching frequencies as high as 5MHz. For systems with higher power requirements, multi-phasing parallel converters is readily implemented.
The LTC3311S uses a constant frequency, peak current mode control architecture for fast transient response. A 500mV reference allows for low voltage outputs. 100% duty cycle operation delivers low drop out.
Other features include a power good signal when the output is in regulation, precision enable threshold, output overvoltage protection, thermal shutdown, a temperature monitor, clock synchronization, mode selection and output short circuit protection. The device is available in a compact 18-lead 3mm × 3mm LQFN package.
- Servers, Telecom Power Supplies
- Distributed DC Power Systems (POL)
- FPGA, ASIC, μP Core Supplies
Product Lifecycle Recommended for New Designs
This product has been released to the market. The data sheet contains all final specifications and operating conditions. For new designs, ADI recommends utilization of these products.
Evaluation Kits (1)
Demonstration Circuit 3018A features the LTC3311S 12.5A, low voltage, synchronous step-down Silent Switcher™ 2 operating as a 2MHz 3.3V to 1.2V 12.5A buck regulator. The LTC3311S supports output voltages from 0.5V to VIN with operating frequencies from 500kHz up to 5MHz. The LTC3311S is a compact, ultralow emission, high efficiency, and high speed synchronous monolithic step-down switching regulator. The integrated bypass capacitors optimize all the fast current loops and make it easier to minimize EMI/EMC emissions by reducing layout sensitivity. Fast minimum on-time of 35ns enables high VIN to low VOUT conversion at high frequency.
DC3018A is set up to run in forced continuous mode with a 2MHz switching frequency but can be configured to pulse skip mode or different switching frequencies. RT is connected to VIN which sets the MODE/SYNC pin as an input and allows the LTC3311S to sync from an external clock. Connecting the MODE/SYNC pin to VIN sets the mode to pulse skip mode and connecting the MODE/SYNC pin to GND sets the mode to forced continuous mode. The Efficiency vs Load graph shows the efficiency and the power loss of the circuit with a 3.3V input in forced continuous mode operation.
The DC3018A also has an EMI filter to reduce conducted EMI. This EMI filter can be included by applying the input voltage at the VIN EMI terminal. The EMI performance of the board is shown in the EMI Test Results section. The red lines in the EMI performance graphs illustrate the CISPR25 Class 5 peak limits for the conducted and radiated emission tests.
The LTC3311S data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with the demo manual. The LTC3311S is assembled in a 3mm × 3mm LQFN package with exposed pads for low thermal resistance. The layout recommendations for low EMI operation and maximum thermal performance are available in the data sheet section Low EMI PCB Layout.
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.
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.
To open the project file for this circuit:
Step 1: Download and install LTpowerCAD on your computer.
Step 2: Click on the link(s) in the section below to download part-specific project files.
Step 3: If the project file doesn't run, right-click the link and select "Save Target As." Then start the LTpowerCAD tool and open the project file by selecing "Open Project" from the "File" menu.
LTpowerCAD Project Files
Design tools for the following parts are available in LTpowerCAD:
Technical Articles (1)
Rarely Asked Questions (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
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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.