Linear Adds New 2.2V Input High Power Step-Down DC-DC Controller

Linear Technology Corp. introduced the LT3740, a high output power step-down synchronous controller that operates from very low input voltages without needing an auxiliary 5V gate drive supply. In addition to a dc-dc step-down controller, the LT3740 integrates a dc-dc step-up converter for generating its own MOSFET gate drive voltage. This function permits the use of inexpensive off-the-shelf 5V gate-drive N-channel MOSFETs, offering up to 3% higher efficiency than sub-logic gate-drive MOSFETs and eliminating the need for a secondary supply.

The LT3740 is suitable for converting input supplies ranging from 2.2 to 22V to an output as low as 0.8V and at load currents from 2 to 20A with 93% typical efficiency. Applications include distributed power systems, point-of-load regulation and conversion of logic supplies. In particular, the LT3740 can step down from 5, 3.3 and 2.5V rails.

The LT3740 operates at a fixed frequency of 300kHz and employs valley current mode control to deliver exceptional transient response and very low on-times. In addition, the LT3740 uses low-side MOSFET current-sense architecture for current limiting and overload protection, eliminating the need for a sense resistor while improving efficiency. Three current limit threshold levels can be selected by connecting the range pin to ground, open or the input voltage. Furthermore, a power good signal is available to monitor the output voltage and the device has a tracking function that allows output voltage control during power up and power down.

The LT3740 is offered in a 16-lead 5mm x 3mm DFN package with an operating temperature range from -40 to 85°C. Pricing starts at $1.95 each in 1,000-piece quantities.