High-Speed Step-Down Controllers with Synchronous Rectification for CPU Power

The MAX1624/MAX1625 are ultra-high-performance, step-down DC-DC controllers for CPU power in high-end computer systems. Designed for demanding applications in which output voltage precision and good transient response are critical for proper operation, they deliver over 35A from 1.1V to 3.5V with ±1% total accuracy from a +5V ±10% supply. Excellent dynamic response corrects output transients caused by the latest dynamically clocked CPUs. These controllers achieve over 90% efficiency by using synchronous rectification. Flying-capacitor bootstrap circuitry drives inexpensive, external N-channel MOSFETs.

The switching frequency is resistor programmable from 100kHz to 1MHz. High switching frequencies allow the use of a small surface-mount inductor and decrease output filter capacitor requirements, reducing board area and system cost.

The MAX1624 is available in a 24-pin SSOP and offers additional features such as a digitally programmable output in 100mV increments; adjustable transient response; selectable 0.5%, 1%, or 2% AC load regulation; and gate drive for a current-boost MOSFET. The MAX1625 is resistor adjustable and comes in a 16-pin narrow SO package. Other features in both controllers include internal digital soft-start, a power-good output, and a 3.5V ±1% reference output. For a similar controller compatible with the latest Intel® VRM/VID specification, see the MAX1638 data sheet.

Applications

* Computers: Desktop, Workstation, Server * GTL Bus Termination * Industrial Computers * LAN Servers * Pentium®

* Better than ±1% Output Accuracy Over Line and Load

* 90% Efficiency

* Excellent Transient Response

* Resistor-Programmable Fixed Switching Frequency from 100kHz to 1MHz

* Over 35A Output Current

* Digitally Programmable Output from 1.1V to 3.5V in 100mV Increments (MAX1624)

* Resistor-Adjustable Output down to 1.1V (MAX1625)

* Remote Sensing

* Adjustable AC Loop Gain (MAX1624)

* GlitchCatcher™ Circuit for Fast Load-Transient Response (MAX1624)

* Power-Good (PWROK) Output

* Current-Mode Feedback

* Digital Soft-Start

* Strong 2A Gate Drivers

* Current-Limited Output