STMicro Adds Tiny Fully-Integrated PWM Controllers To Power Management Portfolio
STMicroelectronics extended its portfolio of power management devices with a new family of PWM (Pulse Width Modulation) controllers intended for motherboard and POL (Point of Load) markets. Four new products – L6726A, L6727, L6728 and L6728A – integrate a voltage reference, control logic, gate drivers, monitoring and protection circuits into standard SO-8 or tiny 3x3mm 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 over-voltage and under-voltage protection.
The L6726A and L6727 are described as low-cost single-phase PWM controllers, with embedded high-current drivers, enabling the easy creation of general purpose dc-dc step-down converters with excellent performance for a broad range of applications – from desktop PC sub-systems, such as memories and chipsets, to general-purpose power supplies. With their high level of integration, these 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 niPOL (non-isolated Point of Load) applications.
The company states that the development of the new family has been carried out in co-operation with key customers, to ensure the optimum combination of features to meet the cost and technical requirements of this high-volume market. In addition to use on server and PC motherboards, the controllers are suitable for modems, set-top boxes (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 more than 30A. They operate over a wide input voltage range of 1.5 to 18V, while the integrated 0.8V voltage reference ensures 1% (L6726A, L6727) or up to 0.8% (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. A range of other features are designed to increase efficiency and reduce the external component count.
The L6726A and L6727 are in volume production now, and are available in an SO-8 package priced at $0.50 in quantities of 1000. Samples of the L6728 and L6728A are available, with volume production in Q4 2007. They are supplied in a 3x3mm DFN package.
