The RT9227A is a 3-in-one power controller optimized
for high-performance microprocessor and computer
applications. The IC integrates a synchronous buck PWM
controller, a linear regulator and a linear controller as well
as monitoring and protection functions into a 24-pin SOP
package. The PWM controller regulates the
microprocessor core voltage. The linear regulator
provides power for the clock driver circuit and the linear
controller regulates power for the GTL bus.
The RT9227A features an Intel-compatible, TTL 5-bit
programmable DAC that adjusts the core voltage from
2.1V to 3.5V in 0.1V increments and from 1.3V to 2.05V
in 0.05V steps. The 5-bit DAC has a typical ±1% tolerance.
The linear regulator uses an internal drive device to
provide a fixed 2.5V ±2.5% output voltage. The linear
controller drives an external N-Channel MOSFET or a low
cost NPN bipolar transistor to provide a fixed 1.5V ±2.5%.
The RT9227A monitors all the output voltages. A Powergood
signal is issued when the core voltage is within ±10%
of the DAC setting and the other levels are above their
under-voltage levels. Additional build-in over-voltage
protection for the core output uses the lower MOSFET to
prevent output voltage above 115% of the DAC setting.
The PWM over-current function monitors the output
current using the voltage drop across the upper
MOSFET's RDS(ON), which eliminates the need for a current
sensing resistor.