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Tiny PWM controllers fit motherboard, POL apps

Posted: 31 Oct 2007 ?? ?Print Version ?Bookmark and Share

Keywords:power management? PWM controllers? pulse width modulation? power supply? MOSFET?

L6726A, L6727

STMicroelectronics has extended its portfolio of power management devices with a new family of flexible and high-performance pulse width modulation (PWM) controllers intended for motherboard and POL markets.

Four new products, namely L6726A, L6727, L6728 and L6728A, integrate a voltage reference, control logic, gate drivers, monitoring and protection circuits into standard SO-8 or tiny 3mm x 3mm DFN packages. Two of the chips offer additional features for high-level applications, including a PowerGOOD output to report power status and the output voltage sense for accurate overvoltage and undervoltage protection.

The L6726A and L6727 are low-cost single-phase PWM controllers, with embedded high-current drivers that enables easy creation of general purpose DC/DC step-down converters for applications in desktop PC sub-systems including memories and chipsets, to general-purpose power supplies. With high level of integration, the compact SO-8 devices allow a significant reduction in the cost and size of the power supply.

The L6728 and L6728A add to the simpler devices the characteristics required by the high-end motherboard market, including plus or minus 0.8% voltage accuracy over line and temperature variations, a PowerGOOD output to provide real-time information on output-voltage status, and the chip-scale 10-lead DFN package. They offer a fixed-frequency 300kHz (L6728) or 600kHz (L6728A) oscillator, for simple but flexible application design. It is the first time that all of these high-level features have been integrated into such a small package, and the devices are particularly suited to servers and non-isolated point of load applications.

In addition to use on server and PC motherboards, the controllers are suited for modems, STBs, consumer applications and advanced DC/DC down-converters.

With embedded high-current, high-speed N-channel MOSFET drivers, the chips can be used in the design of power applications driving a few amps to over 30A. They operate over a wide input voltage range of 1.5V to 18V, while the integrated 0.8V voltage reference ensures 1 percent (L6726A, L6727) or up to 0.8 percent (L6728, L6728A) output accuracy. Sensorless current monitoring, through a low-side power MOSFET, avoids the cost of an external current-sensing resistor and saves board space, and the single- or dual-level over-current protection has programmable thresholds.

The L6726A and L6727 are in volume production now, and are available in SO-8 packages. Pricing starts at 50 cents in quantities of 1,000. Samples of the L6728 and L6728A are available, with volume production slated in Q4. They are supplied in a 3mm x 3mm DFN package.

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