RT9645 pdf datasheet (5 Channe

The RT9645 is a combo regulator which is compliant to
ACPI specification for desktop/server power management
and system application. The part features one switching
regulator for DDR memory VDDQ power; a second PWM
controller for GMCH core power, a LDO controller for
FSB_ VTT termination, a LDO controller for 5VSB to 3VSB
conversion; and a dual power control 5VDL for S0 and S3
system power.
The part is generally operated to conform to ACPI
specification. In S3 mode, only VDDQ and 3.3VSB
regulators remain on while the FSB_ VTT regulator is off.
In the transition from S3 to S0, an internal SS capacitor is
attached for linear regulators to control its slew rate
respectively to avoid inrush current induced.
RT9645 supports both Intel VR11 and AMD K8 platform.
There is extra control pin VTT_EN to enable FSB_VTT
regulator at AMD K8 mode. This part also implements
PWM1 (VDDQ) enabled by release COMP1 at AMD K8
application. This part is assemblyed in the tiny
VQFN-24L 4x4 package.