MSI Z77A-GD65 Motherboard

Voltage Regulator

The CPU voltage regulator circuit of the MSI Z77A-GD65 has eight phases for the CPU main voltage (Vcc a.k.a. Vcore), two for the CPU VSA voltage (memory controller), one for the CPU VTT voltage (PCI Express and DMI interfaces), and one for the CPU integrated video controller (VAXG). Therefore, it uses an “8+2+1+1” configuration.

Figure 8: Voltage regulator circuit

The voltage regulator is controlled by a uP1618A integrated circuit, using a digital design.

Each main phase is controlled by a Renesas R2J20655 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 percent. (Usually, voltage regulator circuits switch at 250 kHz.) Integrated circuits with these characteristics are called “DrMOS.”

This motherboard uses military-class components. Electronic components are available in two series, civilian and military. Military components are more expensive but have tighter tolerance and can withstand a wider range of temperatures. All electrolytic capacitors used in the main voltage regulator circuit are SMD (surface mount device), 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 solid ferrite-core models, also known as SFC, Super Ferrite Choke, which, according to MSI, can provide up to 20% improvement in efficiency.

The motherboard has a series of eight LEDs on its edge near the memory sockets for you to monitor the phases of the CPU Vcc voltage (a.k.a. “core voltage”). This motherboard has a feature called APS (Active Phase Switching) that enables and disables power phases according to the power consumption.

Figure 9: Phase-monitoring LEDs

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