Renesas unveil MCU-Based Scalable Power Supply System Solution

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



Renesas VR 12 solution leverages leadership in MCU, analog, and discrete power device technologies. The Renesas solution is a digital-analog hybrid system that combines the flexibility of MCUs with the stability of analog circuits to achieve precise high-speed control at a low level of current consumption.



Key features of the new chipset:



(1) Approx. 40 percent smaller board area compared to existing Renesas designs



In contrast to conventional technologies that use inductor current to measure output voltage, Renesas’ system uses an intelligent power device, 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 40 A per phase.



(2) Low current for extended battery life in connected-standby mode



Next-generation notebook PCs, tablets and mobile phones require information updates while in standby mode using very little power. Renesas’ R2A30521NP VR controller employs 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 approximately 50 mW in standby mode and approximately 0.8 mW in connected-standby mode.



(3) Support for scalable power supplies with a variety of configurations, enabling customers to extend their product lineups easily



Support for a maximum of two power loops and up to eight phases allows for a wide range of applications extending from 10 W systems such as notebook PCs to 300 W systems such as servers, high-end desktop PCs, and network VRs. Renesas intends to continue expanding its product lineup to provide customers with greater flexibility in response to market demand for more package options as well as enhanced functionality and characteristics for improved performance.



In addition to the above features, the new system has far greater noise tolerance because it requires no external lines for current detection. 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 settings - independent in hardware and software - are supported for protection functions essential to a power supply system, such as overcurrent. 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 widely used compact surface-mount 64-pin QFN (8 mm × 8 mm × 0.95 mm, 0.5 mm 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 mm × 6 mm × 0.95 mm, 0.5 mm pitch) package that has been widely used for earlier mass-produced integrated Driver-MOSFET power devices. 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’ new chipsets are available from October 2012, priced at US$3.50 for the R2A30521NP VR controller and US$2.50 for the R2J20759NP intelligent power device. Mass production of the new products is scheduled to begin in January 2013 and is expected to reach a scale of 500,000 sets per month by December 2013.