GENERAL 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 VDDQ, one DDR/DDR2 bus terminator VTT (equal to VDDQ/2) regulator with source and sinking ability, three LDO controllers for V GMCH (cascode), and GMCH/CPU terminat ion VTT_GMCH/CPU. 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 VGMCHH and RT9644A except VDAC). V DDQ PW M controller and DDR/DDR2 bus terminator regulator have over voltage protection. Moreover, the VDDQ 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.
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