The ISL6524 provides the power control and protection for

four output voltages in high-performance microprocessor

and computer applications. The IC integrates one PWM

controller and three linear controllers, as well as the

monitoring and protection functions into a 28-pin SOIC

package. The PWM controller regulates the microprocessor

core voltage with a synchronous-rectified buck converter.

One linear controller supplies the computer system’s AGTL+

1.2V bus power. The other two linear controllers regulate

power for the 1.5V AGP bus and the 1.8V power for the chip

set core voltage and/or cache memory circuits.

The ISL6524 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 linear

regulators use external N-channel MOSFETs or bipolar NPN

pass transistors to provide fixed output voltages of 1.2V ±3

(VOUT2), 1.5V ±3 (VOUT3) and 1.8V ±3 (VOUT4).

The ISL6524 monitors all the output voltages. A delayedrising VTT (VOUT2 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 undervoltage 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.

Features

• 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 Design

- Voltage-Mode PWM Control

• Fast PWM Converter Transient Response

- High-Bandwidth Error Amplifier

- Full 0 to 100 Duty Ratio

• 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 Monitor

- Switching Regulator Doesn’t Require Extra Current

Sensing Element, Uses MOSFET’s rDS(ON)

• Small Converter Size

- Constant Frequency Operation

- 200kHz Internal Oscillator

• Pb-Free Available (RoHS Compliant)

Applications

• Motherboard Power Regulation for Computers