Out in Front: March 1, 1996

By using constant-frequency operation, a pair of dc/dc converters from Linear Technology provides low-noise 3 to 5V output—especially suitable for applications with audio functions—and high efficiency over a 100-to-1 load range from a 3.5 to 36V input. The LTC1438 (and companion LTC1439, which has some additional features) provides more than 5A of output current at efficiency greater than 90%, using dual synchronous step-down, N-channel MOSFET controllers. Using a few external components, primarily inductors, these converters let you design supplies with one to four separate outputs.

Both converters offer low-battery detection, power-on reset, separate soft start (power-up sequencing), and dropout voltage lower than 200 mV. The LTC1439 converter also includes an auxiliary low-power regulator, which works with an external pnp transistor to provide 12V output at 200 mA, and switching frequency synchronization using an internal PLL. The LTC1438 is available in a 28-lead SSOP package and costs $7 (1000), and the LTC1439 comes in a 36-lead SSOP and costs $7.55 (1000).
—by Bill Schweber

Linear Technology Corp, Milpitas, CA. (408) 432-1900.