Features and Benefits
- Pin Compatible with LTC3307(3A) and LTC3309(6A)
- High Efficiency: 8mΩ NMOS, 31mΩ PMOS
- Programmable Frequency 1MHz to 3MHz
- Tiny Inductor and Capacitors
- Peak Current Mode Control
- 22ns Minimum On-Time
- Wide Bandwidth, Fast Transient Response
- Silent Switcher® Architecture
- Ultralow EMI Emissions
- Low Ripple Burst Mode® Operation with IQ of 40μA
- Safely Tolerates Inductor Saturation in Overload
- VIN Range: 2.25V to 5.5V
- VOUT Range: 0.5V to VIN
- VOUT Accuracy: ±1% Over Temperature Range
- Precision 400mV Enable Threshold, 1μA in Shutdown
- Power Good, Internal Compensation and Soft Start
- Thermally Enhanced 2mm × 2mm LQFN Package
- AEC-Q100 Qualified for Automotive Applications
The LTC3308A is a very small, high efficiency, low noise, monolithic synchronous 4A step-down DC/DC converter operating from a 2.25V to 5.5V input supply. Using constant frequency, peak current mode control at switching frequencies 1MHz to 3MHz and minimum on-time as low as 22ns, this regulator achieves fast transient response with small external components. Silent Switcher architecture minimizes EMI emissions.
The LTC3308A operates in forced continuous or pulse skip mode for low noise, or low-ripple Burst Mode operation for high efficiency at light loads, ideal for battery-powered systems. The IC regulates output voltages as low as 500mV. Other features include output overvoltage protection, short-circuit protection, thermal shutdown, clock synchronization, and up to 100% duty cycle operation for low dropout. The device is available in a low profile 12-lead 2mm × 2mm × 0.74mm LQFN package with exposed pad for low thermal resistance.
- Optical Networking, Servers, Telecom
- Automotive, Industrial, Communications
- Distributed DC Power Systems (POL)
- FPGA, ASIC, μP Core Supplies
- Battery Operated Systems
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 2991A features the LTC3308A 5V, 4A synchronous step-down Silent Switcher® operating as a 2.0MHz, 3.3V to 1.2V 4A buck regulator. The LTC3308A supports adjustable output voltages from 0.5V to VIN with operating frequencies from 1MHz up to 3MHz. The LTC3308A is a compact, ultralow emission, high efficiency, and high speed synchronous monolithic stepdown switching regulator. A minimum on-time switching of 22ns enables high VIN to low VOUT conversion ratios at high frequencies.
The DC2991A operating mode may be selected as BURST, SKIP or Forced Continuous (FC) mode. Setting JP1 to the FC/SYNC position will allow the LTC3308A to sync to a clock frequency from 1MHz to 3MHz. The LTC3308A operates in forced continuous mode when syncing to an external clock. The DC2991A is set to a fixed 2MHz frequency by connecting RT to VIN through a 0Ω resistor, R9. The frequency can be easily changed by removing R9 and setting an appropriate resistor in the R4 location to obtain the desired frequency. Refer to the LTC3308A data sheet for the proper RT value for a desired switching frequency.
The DC2991A 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 LTC3308A data sheet gives a complete description of the device, operation and application information. The data sheet must be read in conjunction with this demo manual. The LTC3308A is assembled in a 2mm × 2mm 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.
The Efficiency vs Load graph shows the efficiency and the power loss of the circuit with a 3.3V input in Burst Mode operation.
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:
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.
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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.