General Description

The MAX8553 is a 4.5V to 28V input-voltage, synchronous step-down controller that provides a complete power-management solution for DDR memory. The MAX8553 generates 1/2 VREFIN voltage for VTT and VTTR. The VTT and VTTR tracking voltages are maintained within 1 of 1/2 VREFIN. The MAX8554 is a 4.5V to 28V input voltage, nontracking step-down controller with a low 0.6V feedback threshold voltage. The MAX8553/MAX8554 use Maxim’s proprietary Quick-PWM? architecture for fast transient response and operate with selectable pseudo-fixed frequencies. Both controllers can operate without an external bias supply.

Features

? Up to 25A Output-Current Capability

? Quick-PWM Control for Fast Loop Response

? Up to 95 Efficiency

? 4.5V to 28V Input Voltage Range

? No External Bias Supply Required

? 0 to 3.6V Input REFIN Range (MAX8553)

? Automatically Sets VTT and VTTR to within ±1 of 1/2 VREFIN- (MAX8553)

? Low 0.6V Feedback Threshold (MAX8554)

? 200kHz/300kHz/400kHz/550kHz Selectable Switching Frequencies

? Adjustable Foldback Current Limit

? Overvoltage Protection

? Digital Soft-Start

Applications

??? Wide-Input Power Supplies

??? Servers and Storage Applications

??? ASIC and CPU Core Voltages

??? Notebook and LCD-PC Power Supplies

??? DDR I and DDR II Memory Power Supplies

??? AGTL Bus Termination Supplies