ISL6523A

• Provides 4 Regulated Voltages
  - Microprocessor Core, AGTL+ Bus, AGP Bus Power,and North/South Bridge Core
• Drives N-Channel MOSFETs
• Linear Regulator Drives Compatible with both MOSFET and Bipolar Series Pass Transistors
• Simple Single-Loop Control Designs
  - Voltage-Mode PWM Control
• Fast PWM Converter Transient Response
  - High-Bandwidth Error Amplifiers
  - Full 0% to 100% Duty Ratios
• Excellent Output Voltage Regulation
  - Core PWM Output . . . . . . . . . . ±1% Over Temperature
  - All Other Outputs . . . . . . . . . . . . . ±3% Over Temperature
• VRM8.5 TTL-Compatible 5-Bit DAC Microprocessor Core Output Voltage Selection
  - Wide Range . . . . . . . . . . . . . . . . . . . . 1.050V to 1.825V
• Power-Good Output Voltage Monitors
  - Separate delayed VTT Power Good
• Overcurrent Fault Monitors
  - Switching Regulators Do Not Require Extra Current Sensing Elements, Use MOSFET's rDS(ON)
• Small Converter Size
  - Constant Frequency Operation
  - 200kHz Internal Oscillator

The ISL6523A provides the power control and protection for four output voltages in high-performance microprocessor
and computer applications. The IC integrates two PWM controllers and two linear controllers, as well as the monitoring and protection functions into a 28-pin SOIC package. One PWM controller regulates the microprocessor core voltage with a synchronous-rectified buck converter.The second PWM controller supplies the computer system's AGTL+ 1.2V bus power with a standard buck converter. The linear controllers regulate power for the 1.5V AGP bus and the 1.8V power for the chipset core voltage and/or cache memory circuits.

The ISL6523A includes an Intel VRM8.5 compatible, TTL 5-input digital-to-analog converter (DAC) that adjusts the microprocessor core-targeted PWM output voltage from 1.050V to 1.825V in 25mV steps. The precision reference and voltage-mode control provide ±1% static regulation. The second PWM controller's output provides a voltage level of 1.2V with ±3% accuracy. The linear regulators use external N-channel MOSFETs or bipolar NPN pass transistors to provide fixed output voltages of 1.5V ±3% (VOUT3) and 1.8V ±3% (VOUT4).

The ISL6523A monitors all the output voltages. A delayedrising VTT (standard buck output) Power Good signal is issued before the core PWM starts to ramp up. Another system Power Good signal is issued when the core is within ±10% of the DAC setting and all other outputs are above their under- voltage levels. Additional built-in overvoltage protection for the core output uses the lower MOSFET to prevent output voltages above 115% of the DAC setting. The PWM controllers' overcurrent function monitors the output current by using the voltage drop across the upper MOSFET's rDS(ON), eliminating the need for a current sensing resistor.