Renesas Launches RL78/G21 MCU with 34 µA/MHz Operating Current

Renesas Electronics has expanded its RL78 family with the RL78/G21, a new 16-bit microcontroller optimized for system control in smart appliances. The device is designed for applications including air conditioners, refrigerators, washing machines and microwave ovens, where low power consumption and peripheral integration are important considerations.

The RL78/G21 achieves an operating current of 34 µA/MHz, nearly half that of the existing RL78/G13, while retaining pin and functional compatibility with the RL78/G13 and RL78/G23 families. Renesas has also introduced new RL78/G23 variants with additional capacitive-touch channels for more advanced human-machine interfaces (HMIs).

Lower Power Consumption and System Integration

The RL78/G21 builds on the low-power technology developed for the RL78 family, with an operating current of just 34 µA/MHz. The reduction in power consumption can help reduce power supply requirements in appliance control systems, while the device's compatibility with existing RL78 MCUs allows designers to move to the new series with minimal changes to their designs.

Available with 128 KB or 256 KB of code flash, the RL78/G21 incorporates a high-speed on-chip oscillator (HOCO) with ±1.0% accuracy and 4 KB of data flash. These integrated functions can eliminate the need for an external oscillator and EEPROM, reducing the number of components required on the board.

The new MCU also adds the UARTA communication interface, an upgrade over the RL78/G13 that supports system expansion through additional devices such as sensors. Its operating voltage range extends from 1.6 V to 5.5 V.

Renesas has specified an electrostatic discharge tolerance of ±4 kV under the Human Body Model (HBM) for the RL78/G21, addressing reliability during manufacturing, assembly and operation. The device also supports self-diagnostic functions through an IEC 60730-compliant self-test library, alongside security features including flash read protection, a flash shield window, Unique ID and Customer ID.

Expanded Capacitive-Touch Support for RL78/G23

Alongside the RL78/G21 launch, Renesas has expanded its RL78/G23 lineup with the R7F104G series, increasing the number of capacitive-touch channels available for appliance interfaces.

The existing RL78/G23 R7F100G devices provide 14 touch channels in the 44-pin version and 16 channels in the 48-pin version. The new R7F104G variants increase these figures to 24 and 25 channels respectively, supporting designs with a greater number of touch inputs.

Renesas provides common touch peripheral functionality and its QE for Capacitive Touch development tool across the RL78, RX and RA microcontroller families.

Both the RL78/G21 and the expanded RL78/G23 devices are available now. Pricing for the RL78/G21 starts at $0.56 for the 128 KB, 44-pin LQFP version and $0.77 for the equivalent 256 KB device, based on 10,000-unit quantities.

Learn more and read the original announcement at renesas.com.

Technology Overview

The Renesas RL78/G21 is a 16-bit microcontroller for low-power system control in smart appliances. It operates at 34 µA/MHz, nearly half the current of the RL78/G13, and offers 128 KB or 256 KB code flash, a ±1.0% on-chip oscillator, 4 KB data flash and ±4 kV HBM ESD tolerance. The expanded RL78/G23 R7F104G series adds capacitive-touch configurations supporting up to 25 channels for appliance HMIs.

FAQs

How much power does the Renesas RL78/G21 consume?

The RL78/G21 has an operating current of 34 µA/MHz, nearly half that of the earlier RL78/G13. It is designed for low-power system control in applications such as refrigerators, washing machines and air conditioners.

What features can reduce external component requirements in RL78/G21 designs?

The RL78/G21 includes a high-speed on-chip oscillator with ±1.0% accuracy and 4 KB of data flash. These functions can remove the need for an external oscillator and EEPROM in suitable applications.

How does the new RL78/G23 differ from existing versions?

The new RL78/G23 R7F104G devices increase capacitive-touch support to 24 channels in the 44-pin version and 25 channels in the 48-pin version. Earlier R7F100G devices provide 14 and 16 channels respectively.