Robust control algorithm added to Renesas RX63T MCU

The PWM delay generation function enables high-resolution adjustment of PWM output in increments as small as 312.5 picoseconds (one-trillionth of a second), allowing more precise and optimized power control. The digital power management control function entails the integration of a digital power management controller in hardware. It provides a robust control algorithm that automatically compensates for inconsistency in the characteristics of the elements within the power supply unit. This results in enormous savings, since the system design engineering can reduce the man-hours work required for manual tuning of the power supply. The new functions are both driven by high-speed hardware, which allows the use of higher switching frequencies and contributes to more compact power supply dimensions.

Due to the global warming and energy shortages, demands for more eco-friendly lifestyle are rising. There is emphasis on adding energy-saving functions to electric household appliances and consumer products such as air conditioners and refrigerators. At the same time, there is demand for low-power design in embedded devices used in industrial equipment. As a way to reduce power consumption, digital control is increasingly being adopted as an alternative to conventional analog power supply configurations. As a result, increasing importance is being placed on more precise power management control to boost efficiency, achieve greater compactness, and improve design efficiency.

Although MCUs have been used to implement digital power management control, the number of MCU models capable to perform the high-resolution PWM control required for this purpose was limited. In addition, precise tuning is required to match the load characteristics of the device subject to power management control. A special tuning process was required to compensate for inconsistency in the characteristics (deviation from the design values) of the elements within the power supply unit. Also, digital power management control requires complex calculations for feedback control. Since the processing needs to be done in software, higher performance controller would be demanded. Renesas provides with the RX63T MCU, the latest evolution of the wide scalable RX 32-bit family, such high resolution PWM timer, 100MHz CPU performance and all tuning mechanism to design a highly efficient single chip solution.

Key Features of the new PWM delay generation function and DPC function on the RX63T Group of MCUs:

1) High-resolution 312.5-picosecond PWM output function

PWM output precision (resolution) is essential for power management control, and the new PWM output function achieves a maximum resolution of 312.5 picoseconds (100 MHz operation). This high-resolution PWM output function, when combined with the excellent CPU performance of Renesas’ RX core, enables a higher level of precision for inverter and converter control. This enables highly efficient digital power management in applications such as server power supplies and general-purpose power supply systems.

2) Robust control algorithm to compensate for inconsistency in the characteristics of the elements on the user board

Implementing  the control algorithm required by the digital power supply in hardware enables achieving greater compactness and on the other hand to use the faster switching frequencies needed for higher precision (maximum: 1.85 MHz). The robust control algorithm automatically compensates for inconsistency in the characteristics of the individual elements in the customer’s system, realizing a high level of stability. This eliminates the need for system designers to perform tuning after mounting the power supply ICs. This results in dramatic reduction of man-hours. The above functions are implemented in hardware, so the powerful processing capabilities of the 32bit RX core can be applied to the main processing routine (motor/inverter control, etc.) while DC/DC power management control takes place simultaneously.

For an easy development start, a RX63T starter kit is provided. For debugging purpose, two products are available by Renesas: the low-cost E1 Emulator, which also functions as a flash programmer, and the high-functionality E20 Emulator, which includes trace, RAM monitoring, and other advanced functions. Third party J-Link debuggers are also available.

Sampling of the new RX63T Group with the new added functions started in September 2013.