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