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The ISL6537A 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 V_DDQ during S0/S1 and S3 states. During S0/S1 state, a fully integrated sink-source regulator generates an accurate (V_DDQ/2) high current V_TT voltage without the need for a negative supply. A buffered version of the V_DDQ/2 reference is provided as V_REF. A second PWM controller, which requires external MOSFET drivers, is available for regulation of the GMCH Core voltage. An LDO controller is also integrated for the CPU V_TT termination voltage regulation and the DAC.

The switching PWM controller 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 and CPU V_TT termination voltage is within spec and operational.

All outputs, except VDAC, have undervoltage protection. The switching regulator also has overvoltage and overcurrent protection. Thermal shutdown is integrated.

Key Features

• Generates 5 Regulated Voltages
  • Synchronous Buck PWM Controller for DDR VDDQ
  • 3A Integrated Sink/Source Linear Regulator with Accurate VDDQ/2 Divider Reference for DDR VTT
  • PWM Regulator for GMCH Core
  • LDO Regulator for CPU/GMCH VTT Termination
  • LDO Regulator for DAC
• ACPI Compliant Sleep State Control
• Glitch-Free Transitions During State Changes
• Integrated VREF Buffer
• VDDQ PWM Controller Drives Low Cost N-Channel MOSFETs
• 250kHz Constant Frequency Operation
  • Both PWM Controllers are Phase Shifted 180°
• 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
• OCP on the VDDQ Switching Regulator
• Integrated Thermal Shutdown Protection
• Pb-Free Plus Anneal Available (RoHS Compliant)

Applications

• Single and Dual Channel DDR Memory Power Systems in ACPI Compliant PCs
• Graphics Cards - GPU and Memory Supplies
• ASIC Power Supplies
• Embedded Processor and I/O Supplies
• DSP Supplies