Gigabyte 990FXA-UD5 Motherboard

Voltage Regulator

The CPU voltage regulator circuit of the 990FXA-UD5 has eight phases for the CPU main voltage (VDD a.k.a. Vcore) and two for the CPU VDDNB voltage (integrated memory controller, HyperTransport bus controller, and L3 memory cache). Therefore, it uses an “8+2” configuration.

Figure 8: Voltage regulator circuit

Figure 9: Voltage regulator circuit

This motherboard uses solid ferrite-core coils, which present less energy loss than iron-core coils (i.e., they improve efficiency), and solid capacitors. Each main phase is controlled by an SiC769CD integrated circuit, which combines the three required transistors (“high side,” “low side,” and “driver”) in a single chip. It also allows the switching clock to be at 1 MHz, which allows efficiency to be over 90%. (Usually, voltage regulator circuits switch at 250 kHz.) Integrated circuits with those characteristics are known as “DrMOS.”

If you want to learn more about the voltage regulator circuit, please read our tutorial on the subject.