Intel DX79SI Motherboard

Voltage Regulator

The CPU voltage regulator circuit of the Intel DX79SI has six phases for the CPU main voltage (Vcc a.k.a. Vcore), one for the CPU VSA voltage (memory controller), and one for the CPU VTT voltage (PCI Express and DMI interfaces). Therefore, it uses a “6+1+1” configuration. The voltage regulator is controlled by a CHiL CHL8328 integrated circuit.

Figure 8: Voltage regulator circuit

All electrolytic capacitors used in the main voltage regulator circuit are SMDs (surface mount devices), also known as highly-conductive polymerized or simply Hi-c, but the other voltage regulators (memory, chipset, etc.) use solid capacitors. All coils on this motherboard are ferrite-core models, which can provide up to 20% improvement in efficiency.

Each main phase is controlled by a Renesas R2J20657 integrated circuit (click here for a detailed description), 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 percent. (Usually, voltage regulator circuits switch at 250 kHz.)

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