Features and Benefits
- Wide Input Voltage Range:
- LT1940: 3.6V to 25V
- LT1940L: 3.6V to 7V
- Two 1.4A Output Switching Regulators with Internal Power Switches
- Constant 1.1MHz Switching Frequency
- Anti-Phase Switching Reduces Ripple
- Independent Shutdown/Soft-Start Pins
- Independent Power Good Indicators Ease Supply Sequencing
- Uses Small Inductors and Ceramic Capacitors
- Small 16-Lead Thermally Enhanced TSSOP Surface Mount Package
The LT1940 is a dual current mode PWM step-down DC/DC converter with internal 2A power switches. Both converters are synchronized to a single 1.1MHz oscillator and run with opposite phases, reducing input ripple current. The output voltages are set with external resistor dividers, and each regulator has independent shutdown and soft-start circuits. Each regulator generates a power-good signal when its output is in regulation, easing power supply sequencing and interfacing with microcontrollers and DSPs.
The LT1940’s 1.1MHz switching frequency allows the use of tiny inductors and capacitors, resulting in a very small dual 1.4A output solution. Constant frequency and ceramic capacitors combine to produce low, predictable output ripple voltage. With its wide input range of 3.6V to 25V, the LT1940 regulates a wide variety of power sources, from 4-cell batteries and 5V logic rails to unregulated wall transformers, lead acid batteries and distributed-power supplies. The LT1940L is intended to operate from regulated 5V supplies. A current mode PWM architecture provides fast transient response with simple compensation components and cycle-by-cycle current limiting. Frequency foldback and thermal shutdown provide additional protection.
- Disk Drives
- DSP Power Supplies
- Wall Transformer Regulation
- Distributed Power Regulation
- DSL Modems
- Cable Modems
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 519 is a 1.1MHz dual step-down DC/DC switching converter using the LT1940. The LT1940 features fast switching speed, two 1.6A internal power switches, and a wide input voltage range. The demonstration board has two circuits to demonstrate both the small space that the monolithic dual step-down converter can achieve with high currents and a single IC as well as the versatility and maximum power output of the IC. The circuit demonstrating smallest size generates 3.3V at up to 1A and 1.8V at up to 1A output from a 4.8V to 14V input. The larger, more versatile circuit generates 5V at up to 1.4A and 3.3V at up to 1.4A output from a separate 6.8V to 25V input. The two circuits are completely isolated from each other and can be run simultaneously or independently.
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.
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.