Nov 02, 2004 
The first true direct replacements for the industry-standard UCC380x and UCC280x families of low-power current-mode controllers, the new SiP280x pulse-width modulation (PWM) controllers serve as versatile, low-cost building blocks for a broad variety of converters in both offline and dc-to-dc current-mode switching power supplies in industrial, fixed telecom, and datacom applications. These devices also are suitable for point of load (POL) regulation; high-efficiency dc-to-dc converter modules; and buck, boost, flyback, and forward converters.
Siliconix's pin-for-pin-compatible replacements to the UCC380x/UCC280x family include the SiP2800, SiP2801, SiP2802, SiP2803, SiP2804, and SiP2805, each of which is built on a BiCMOS process and available in either a SO-8 or TSSOP-8 package. Intended for 10-W to 250-W power supplies, the new controllers can operate from a supply voltage as low as 5 V.
The SiP280x series provides improved power supply efficiency relative to the older UC384x/UC284x devices by taking advantage of Siliconix's advanced BiCMOS design and processing. This yields significantly lower start-up and operating current requirements of 100 microamps and 500 microamps respectively. The low start-up current substantially reduces dissipation in any dropping resistors required for start-up of the part, while the minimized operating current drastically cuts the amount of power that must be supplied to a SiP280x controller merely to power the IC. The lower start-up and operating currents additionally allow the SiP280x devices to use smaller external capacitors from the VCC pin to ground.
The BiCMOS process with which these parts are built and their on-chip +/-1-A totem-pole output drivers enable the SiP280x controllers to operate usefully at frequencies up to 1 MHz. This ability for higher-frequency operation allows the use of smaller power inductors and capacitors in many power supply designs.
With an internal soft-start mechanism that is active at power-on and under fault conditions, the SiP280X controllers reduce stress on external components, thereby enhancing power supply performance and reliability. The new ICs also feature built-in leading-edge blanking on the current sense pin. This blanking eliminates the need for external filter components while keeping voltage spikes from triggering the parts' current comparators, ensuring that the current-regulation loop and the overcurrent limiter circuits function properly.
The SiP280x family's combination of automatic soft-start and leading-edge blanking simplifies circuit design. As a result, designers are able to optimize power supply performance for normal operating conditions, with reduced component count as compared to previous solutions. At the same time, the ICs provide an automatic and elegant "hiccup-mode" protection (overcurrent shutdown with soft-start retry) feature that protects the supply and its load during severe fault conditions.
The SiP280x series also features a variety of turn-on and turn-off thresholds to accommodate various supply voltage, UVLO, and hysteresis requirements. The controllers are rated for an operating temperature range of -40 to +85 degrees Celsius.
Samples and production quantities of the SiP280x controllers are available now, with lead times of 8 to 12 weeks for larger orders. Pricing for U.S. delivery is $1.50 for quantities of 1,000 pieces or more.
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Siliconix is a leading manufacturer of power MOSFETs, power ICs, analog switches, and multiplexers for computers, cell phones, fixed communications networks, automobiles, and other consumer and industrial electronic systems. With 2003 worldwide sales of $392.1 million, the Company's facilities include a Class 1 wafer fab dedicated to the manufacture of power products in Santa Clara, California, and an affiliated Class 1 wafer fab located in Itzehoe, Germany. The Company's products are also fabricated by subcontractors in Japan, Germany, China, Taiwan, and the United States. Assembly and test facilities include a company-owned facility in Taiwan, a joint venture in Shanghai, China, and subcontractors in the Philippines, China, Taiwan, and Israel.
Vishay, a Fortune 1,000 Company listed on the NYSE, is one of the world's largest manufacturers of discrete semiconductors (diodes, rectifiers, transistors, optoelectronics, and selected ICs) and passive electronic components (resistors, capacitors, inductors, and transducers). The Company's components can be found in products manufactured in a very broad range of industries worldwide. Vishay is headquartered in Malvern, Pennsylvania, and has plants in 17 countries employing over 27,000 people. Vishay can be found on the Internet at http://www.vishay.com.
