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Renesas boasts MCU-based power supply sol'n

Posted: 15 Oct 2012 ?? ?Print Version ?Bookmark and Share

Keywords:MCU-based power supply? R2A30521NP? R2J20759NP? PWM-driver-MOSFET?

Renesas Electronics Corp. has unleashed a chipset implementing the voltage regulator (VR) aimed at CPU power supplies used in PCs, servers and storage systems. It comprises the R2A30521NP, the industry's first VR controller that integrates an MCU-based digital interface, and the R2J20759NP, an intelligent pulse width modulation (PWM)-driver-MOSFET device (DrMOS) with an integrated current detection circuit, indicated the company.

Renesas intends to supply the chipset as a system solution that enables power supply systems conforming to VR12.0, VR12.5 and the latest VR12.6 VR standards from Intel to achieve greater power density, better power efficiency and more precise operation.

According to the company, the chipset has about 40 per cent smaller board area compared to existing Renesas designs. In contrast to conventional technologies that use inductor current to measure output voltage, Renesas' system uses the R2J20759NP that has its own built-in current detection circuit, eliminating the need for current detection lines on the board or filters to reduce noise. In addition, the intelligent power device R2J20759NP has a compact QFN40 package and can supply up to 40A per phase.

Renesas' R2A30521NP VR controller uses the same architecture as the RL78 MCU, which is equipped with an ultra-low-power mode. When used in combination with the R2J20759NP, power consumption for the VR power supply overall can be reduced to nearly 50mW in standby mode and about 0.8mW in connected-standby mode.

Support for a maximum of two power loops and up to eight phases allows for a range of applications extending from 10W systems such as notebook PCs to 300W systems such as servers, high-end desktop PCs and network VRs.

In addition to the above features, the system has far greater noise tolerance because it requires no external lines for current detection, indicated the company. This contrasts with typical designs in which the lines on the board used for current detection are highly susceptible to external noise such as switching noise generated by the power MOSFETs, a point that must be considered carefully when designing the board layout. Also, with conventional current detection methods that use the inductance of resistors connected in series, there are persistent worries that the setting value of the external current detection circuit could cause malfunctions when changing modes or during detection of current imbalances. The new system allows direct detection of the drain current of the integrated power MOSFETs, avoiding these problems.

Two-stage settingsindependent in hardware and softwareare supported for protection functions essential to a power supply system such as over-current. For example, a steady-state limit value and a limit value for an anticipated sudden and destructive abnormal mode can be set independently. This flexible approach to power supply settings preserves both safety and practicality. The R2A30521NP VR controller also has on-chip flash memory and supports an event logging function that automatically stores event information in the flash memory when protection function operation is detected. The log data can be read via a serial interface such as I2C. This capability has wide applicability for system maintenance, protection circuit history checking, etc.

The VR controller R2A30521NP uses a serial interface to exchange power or system status information with the CPU or other high-level system, and based on this information, it uses a dedicated clock for switching the operating mode. This ensures that the operating mode is always optimal for the power device. In addition, by making use of the features of the MCU-based VR controller, parameters such as operating frequency or protection function setting values can be changed by using software. The package is a surface-mount 64-pin QFN (8 x 8 x 0.95mm, 0.5mm pitch).

As the power block, the intelligent power device R2J20759NP intelligent integrated driver-MOSFET power device combines the capabilities of a conventional integrated driver-MOSFET power device with additional functions such as a current detection circuit and PWM control circuit. This product uses the same 40-pin QFN (6 x 6 x 0.95mm, 0.5mm pitch) package. By integrating the current detection circuit and PWM control circuit into the power device, it is possible to entirely eliminate the noise-sensitive wiring that was necessary when the current detection circuit and PWM control circuit were mounted separately on the system board. This helps to simplify the circuit design of the VR power supply and the board layout design.

Samples of the Renesas' chipsets are available from October, priced at $3.50 for the R2A30521NP VR controller and $2.50 for the R2J20759NP intelligent power device. Mass production of the new products is scheduled to begin in January 2013.





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