LT1940

· Wide Input Voltage Range: 3.6V to 25V
· 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

· Disk Drives
· DSP Power Supplies
· Wall Transformer Regulation
· Distributed Power Regulation
· DSL Modems
· Cable Modems

V_IN Voltage ..................................................... (0.3), 25V
BOOST Pin Voltage ...................................................... 35V
BOOST Pin Above SW Pin ............................................. 25V
PG Pin Voltage ............................................................. 25V
RUN/SS, FB Pins ............................................................. 6V
SW Voltage ....................................................................V_IN
Maximum Junction Temperature .............................. 125°C
Operating Temperature Range (Note 2) ...40°C to 85°C
Storage Temperature Range ..................65°C to 150°C
Lead Temperature (Soldering, 10 sec)..................... 300°C

The LT^®1940 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 powergood 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. 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.