AIC1571

The AIC1571 combines a synchronous voltage mode controller with two linear controllers as well as the monitoring and protection functions in this chip. The PWM controller regulates the microproc-essor core voltage with a synchronous rectified buck converter. One linear controller regulates power for the GTL bus and the other linear control-ler provides power for the clock driver circuit or memory (1.8V)

An integrated 5 bit D/A converter that adjusts the core PWM output voltage from 2.1V to 3.5V in 0.1V increments and from 1.3V to 2.05V in 0.05V increments. The linear regulator uses an internal driver AIC1571 to provide 2.5V2.5%. The linear controller drives with an external N-channel MOSEFET to provide 1.5V2.5%.

AIC1571 monitors all the output voltages. Power Good signal is issued when the core voltage is within 10% of the DAC setting and the other lev-els are above their under-voltage levels. Over-voltage protection for the core output uses the lower N-channel MOSFET to prevent output volt-age above 115% of the DAC setting.
The PWM over-current function monitors the out-put current by using the voltage drop across the upper MOSFETs RDS(ON), eliminating the need for a current sensing resistor.