ISL6548

• Generates 4 Regulated Voltages
- Synchronous Buck PWM Controller for DDR VDDQ
- 3A Integrated Sink/Source Linear Regulator with Accurate VDDQ/2 Divider Reference for DDR VTT
- LDO Regulator for GMCH Core
- Sink/Source LDO Regulator for CPU/GMCH VTT Termination
• ACPI compliant sleep state control
• Glitch-free Transitions During State Changes
• PWM Controller Drives Low Cost N-Channel MOSFETs
• 250kHz Constant Frequency Operation
• Tight Output Voltage Regulation
- All Outputs: ±2% Over Temperature
• Fully-Adjustable Outputs with Wide Voltage Range: Down to 0.8V supports DDR and DDR2 Specifications
• Simple Single-Loop Voltage-Mode PWM Control Design
• Fast PWM Converter Transient Response
• Under and Overvoltage Monitoring on All Outputs
• OCP on the Switching Regulator
• Integrated Thermal Shutdown Protection
• Pb-Free Available (RoHS Compliant)

The ISL6548 provides a complete ACPI compliant power solution for up to 4 DIMM dual channel DDR/DDR2 Memory systems. Included are both a synchronous buck controller to supply VDDQ during S0/S1 and S3 states. During S0/S1 state, a fully integrated sink-source regulator generates an accurate (VDDQ/2) high current VTT voltage without the need for a negative supply. Two LDO controllers are also integrated for the GMCH core voltage regulation and for the GMCH/CPU VTT termination voltage regulation.

The switching PWM controller ISL6548 drives two N-Channel MOSFETs in a synchronous-rectified buck converter topology. The synchronous buck converter uses voltagemode control with fast transient response. The switching regulator provides a maximum static regulation tolerance of ±2% over line, load, and temperature ranges. The output is user-adjustable by means of external resistors down to 0.8V.

An integrated soft-start feature brings all outputs into regulation in a controlled manner when returning to S0/S1 state from any sleep state. During S0 the VIDPGD signal indicates that the GMCH/CPU VTT termination voltage is within spec and operational.

Each output is monitored for undervoltage events. The switching regulator ISL6548 also has overvoltage and overcurrent protection. Thermal shutdown is integrated.