Santa Clara, Calif. - National Semiconductor Corp.'s LM5007 buck dc/dc regulator IC is said to break new ground with its ability to step down from an 80-volt primary-side power supply and produce a low-voltage (10-V typical) bias supply for secondary-side control devices at a cost of less than a dollar in large volume quantities.
Fully integrated with all the functions needed for a high-voltage power supply, the device contains an 80-V n-channel power MOSFET rated at 700-milliamps peak that can be switched at high frequencies of up to 500 kHz. National said this lets a small output filter complete an efficient (more than 90 percent), cost-effective bias supply solution in a minimal printed circuit board space in next-generation telecommunications and 42-V automotive applications.
The regulator, to be launched Aug. 4 using the company's 80-V analog BCD process, is based on a hysteretic control scheme using an ON time inversely proportional to Vin. This feature allows the operating frequency to remain relatively constant. The hysteretic control requires no control-loop compensation, with fast transient response. An intelligent current limit is implemented with forced OFF time, which is inversely proportional to Vout. This current-limiting scheme provides minimum foldback. The regulator's power MOSFET is rated at 80 V with 700-milliohm on-resistance, making it suitable for high-density, high-efficiency power converters. Also integrated in the chip are a wide-range 9-V-to-75-V startup bias regulator, overtemperature shutdown and intelligent current limit timers.
Offered in a tiny (4-mm x 4-mm) eight-pin mounted leadless lead frame chip-scale package to eliminate heat sinks, the device is said to outperform existing buck regulator solutions in FET breakdown, boost diode, soft start and thermal protection.
The device is also available in the MSOP-8 package.
The chip's wide unregulated input operating voltage makes it suitable for battery-powered applications and versatile for any distributed power bus (9 V through 75 V), National said.
The chip is priced at 90 cents per unit in quantities of 10,000. In lots of 500,000 devices, the price will drop to between 75 and 80 cents .
National's high-voltage regulator product road map shows a 100-V device in development. The next-generation part, which is likely to be called the 5008, is now tentatively planned for early 2004 introduction.
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