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