Out in Front: May 23, 1996
The LM2825 dc/dc power converter from National Semiconductor comes in a 24-pin DIP package, thus minimizing design time, cost, and board space. The step-down converter provides output of 3.3 or 5V, depending on model, at 1A from an input as high as 40V. The device requires no external components: The molded package includes active circuitry plus four traditionally external discrete components. Tests rate this supply at a 20-million-hour MTBF, which compares to that of an IC alone and is far greater than MTBFs for assembled modules.The 6g, 80%-efficient design provides power density of 35W/in.3 and requires no heat sink. Output-voltage tolerance is ±4%, and the output is fully protected from excessive-load, short-circuit, and overtemperature fault conditions. In shutdown mode, the device consumes 65 µA. Radiated EMI emission levels are within CISPR (International Special Committee on Radio Structure) Class B limits. The data sheet shows detailed pc-board layout for optimal electrical and thermal performance; many of the 24 leads of the DIP package work in parallel to enhance current-carrying capacity for the VIN, VOUT, or ground connections.
The LM2825 in 3.3 and 5V versions costs $8.65 (1000). The company plans to introduce adjustable and 12V versions this year.
—by Bill Schweber
National Semiconductor Corp, Santa Clara, CA. (800) 272-9959), http://www.national.com..