RT9644/RT9644A

Description

The RT9644/A is a complete ACPI compliant power solution for DDR and DDR2 memory system with up to 4 DIMMs dual channel systems. This RT9644 includes one synchronous buck controller for DDR/DDR2 V_DDQ, one DDR/DDR2 bus terminator V_TT (equal to V_DDQ/2) regulator with source and sinking ability, three LDO controllers for V_GMCH (cascode), and GMCH/CPU termination V_{TT_GMCH/CPU}. The RT9644A includes one synchronous buck controller for DDR/DDR2 V_DDQ, one PWM controller for V_GMCH (with external MOSFET driver), one DDR/DDR2 bus terminator V_TT (equal to V_DDQ/2) regulator with source and sinking ability, and two LDO controllers for V_{TT_GMCH/CPU} and V_DAC.
These parts also provide a reference buffer for DDR/DDR2 input reference voltage generator. When during S0 state, the VIDPGD indicates the GMCH_CPU V_TT within spec and operational. The synchronous buck DC-DC PWM is implemented by two N-MOSFETs as upper and lower MOSFETs with voltage mode control. The linear controllers are implemented with one N-MOSFET with suitable capacitance. Each output is monitored by under voltage protection (RT9644 except V_GMCHHand RT9644A except V_DAC). V_DDQ PWM controller and DDR/DDR2 bus terminator regulator have over voltage protection. Moreover, the V_DDQ PWM controller has the over current protection by external resister adjustment. Thermal shut down is integrated. All the internal voltage reference is fixed at 0.8V, and users can adjust the resistance divider for desired voltage output.