The ISL6537 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 VDDQduring S0/S1 and S3 states. During S0/S1 state, a fully integrated sink-source regulator generates an accurate (VDDQ/2) high current VTTvoltage without the need for a negative supply. A buffered version of the VDDQ/2 reference is provided as VREF. Two LDO controllers are also integrated for the GMCH core voltage regulation and for the GMCH and CPU VTTtermination voltage regulation. The switching PWM controller drives two N-Channel MOSFETs in a synchronous-rectified buck converter topology. The synchronous buck converter uses voltage-mode 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 and CPU VTTtermination voltage is within spec and operational. Each output is monitored for undervoltage events. The switching regulator also has overvoltage and overcurrent protection. Thermal shutdown is integrated.