Renesas Electronics Introduces New CMOS Isolator Technology that Realizes Highly-Integrated Inverter Circuits for Energy-Efficient Home Appliances and Electric Vehicles

Enables Implementation of Compact, High-Speed, and High-Voltage Isolator in Standard CMOS

20 Jul 2010

TOKYO, Japan, July 20, 2010 — Renesas Electronics Corporation (TSE: 6723) today announced the development of CMOS isolator technology using on-chip transformers based on standard CMOS to achieve higher speeds and higher integration densities in inverter circuits. Based on this newly developed technology, Renesas Electronics has developed a prototype isolator chip, confirming its basic operation.

With the increasing awareness for green electronics that promote effective utilization of electrical energy, inverter circuits that provide fine-tuned control of motor speed as required by applications are now adapted widely among energy-efficient products such as air conditioners, refrigerators, electric vehicles, and hybrid electric vehicles. An inverter circuit consists of a high-voltage circuit that controls the on/off state of the voltage applied to the motor, in which the control voltage ranges from a few hundred to a few thousand volts, and a microcontroller (MCU) operating at only a few volts.

Since the voltage difference between the high-voltage circuit and the MCU is very large, an isolator that transfers data between the high-voltage circuit and MCU in an electrically isolated state is required. However, owing to the large size of the existing isolators, it has been difficult to integrate the MCU with multiple high-voltage circuits and isolators in a single package.

An on-chip transformer is a key element of an isolator that can be mounted in a system LSI, and the transformer dominates the circuit area. Therefore, to realize highly-integrated system LSI, it is necessary to reduce the size of the transformer.

However, as the size of the transformer is reduced, its operation frequency exceeds the limit of the frequency that can be received through digital circuits.

The newly developed CMOS isolator technology resolves these problems through the following features.


  • (1) High-frequency transmitter circuit that drives the compact transformer
    Renesas Electronics' new technology makes it possible to transfer high-frequency signals that had previously been hard to transmit through digital circuits by using the high frequency components generated from a low frequency digital input signal with sharp rise.


  • (2) Receiver circuit that detects high-frequency pulse that passed through a compact transformer
    The new CMOS isolator technology enables the high-frequency signals that pass through a compact transformer to be detected by a signal receiver circuit consisting of a junction diode and passive components, which transforms the signals into low-frequency signals that can be handled by digital circuits.


The new CMOS isolator technology increases the frequency of the signals that pass through the transformer, which allows the transformer to reduce the isolator area to 1/4 to 1/8 that of existing isolators. In addition, the compact transformer operating at high frequency allows the isolators to operate at high-speed.

Renesas Electronics' new technology enables integration of the discrete components of an inverter, including an MCU, multiple isolators, and high-voltage circuits, in a single package, making it possible to achieve further miniaturization and reduction in costs for inverter circuits in energy-saving home appliances, electric and hybrid cars, solar panels, and other products, as well as for the switching power supplies used in a wide range of electronic equipment. The new technology can also be used to implement the high-speed communication interfaces used in medical and industrial equipment or isolated interfaces inside display interfaces that require both high-voltage and high-speed drive. Furthermore, the new technology can also be applied in compact and low-loss inverter circuits using next-generation devices that require high-speed operation under high temperature, as well as the elemental technologies for smart grids, including batteries, DC supply systems, and isolated components such as smart meters.

Renesas Electronics believes the new technology will contribute as a basic technology for green electronics for an energy-efficient society. Renesas Electronics also sees it as creating business synergies with the company's core-competent MCUs, SoC solutions and analog & power devices, and will continue to advance its research and development activities in this area.

Renesas Electronics presented the results of this research at the Symposium on VLSI Circuits, which was held in Honolulu, Hawaii from June 16 to June 18.


About Renesas Electronics Corporation

Renesas Electronics Corporation (TSE: 6723) delivers trusted embedded design innovation with complete semiconductor solutions that enable billions of connected, intelligent devices to enhance the way people work and live. A global leader in microcontrollers, analog, power, and SoC products, Renesas provides comprehensive solutions for a broad range of automotive, industrial, infrastructure, and IoT applications that help shape a limitless future. Learn more at Follow us on LinkedIn, Facebook, Twitter, and YouTube.

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