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 VREFINvoltage 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.The controllers operate in synchronous-rectification mode to ensure balanced current sourcing and sinking capability of up to 25A. The MAX8553/MAX8554 also provide up to 95% efficiency, making them ideal for server and point-of-load applications. Additionally, a low 5µA shutdown current allows for longer battery life in notebook applications. Lossless current monitoring is achieved by monitoring the low-side MOSFET's drain-to-source voltage. The MAX8553/MAX8554 have an adjustable foldback current limit to withstand a continuous output overload and short circuit. Digital soft-start provides control of inrush current during power-up. Overvoltage protection shuts the converter down and discharges the output capacitor. The MAX8553/MAX8554 come in space-saving 16-pin QSOP packages.ApplicationsAGTL Bus Termination SuppliesASIC and CPU Core VoltagesDDR I and DDR II Memory Power SuppliesNotebook and LCD-PC Power SuppliesServers and Storage ApplicationsWide-Input Power Supplies