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Step-down regulators integrate low-on-resistance MOSFETs

Posted: 12 Dec 2007 ?? ?Print Version ?Bookmark and Share

Keywords:dual 3A/5A? 2MHz step-down regulators? integrate low-on-resistance MOSFETs?

Maxim Integrated Products has rolled out two step-down regulators that integrate low-on-resistance MOSFETs. The MAX8833/MAX8855 feature the industry's highest integration, and provide the smallest dual power supply for dual 3A/5A loads. The integrated MOSFETs provide high efficiency and minimize space consumption. They are ideal for DDR memories, processors that require more than one rail, and high-end enterprise equipment.

The MAX8833/MAX8855 operate from 3.3V or 2.5V inputs, provide dual 3A or dual 5A outputs (respectively), and integrate switches that maximize space savings. In addition to saving space, the use of internal MOSFETs enables these devices to operate efficiently from low input voltages, which is not possible with large, discrete MOSFETs. Internal MOSFETs provide much better performance in low-voltage applications compared to their discrete counterparts, which require higher voltages for full enhancement. With low on-resistances of 49m? and 37m?, respectively, the MAX8833/MAX8855 are capable of providing efficiencies in the mid-90 percent range while switching above 1MHz. The low on-resistance, high efficiency, and small package of these devices make them ideal for DDR power supplies, processors that require more than one rail, and high-end enterprise equipment.

To increase design flexibility, each device provides a programmable frequency up to 2MHz and an external frequency-synchronization input. An external reference input enables the implementation of tracking applications, such as DDR power supplies, by allowing one channel to power Vddq while the tracking channel powers Vtt. Programmable soft-start for each channel supports a wide range of outputs, further enhancing flexibility. Additionally, a separate power-good signal and enable input for each output ensure simple sequencing. The MAX8833/MAX8855 also combine a high-bandwidth, voltage-error amplifier with high-frequency switching to allow the use of ceramic capacitors that have minimal values.

The MAX8833/MAX8855 are fully specified over the -40C to +85C extended temperature range. Each voltage regulator is available in a 5mm x 5mm, 32pin TQFN package to allow interchangeability as current requirements change. Pricing starts at $2.59 for the MAX8833 and $3.41 for the MAX8855 (10,000-up, FOB USA).

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