Renesas’ RL78/L23 is a low-power 16-bit MCU with built-in segment LCD, capacitive touch, dual-bank flash for FOTA, and a wide 1.6–5.5 V operating voltage range. It targets HMI appliances, metering, and low-cost IoT products with support up to 2037.
Key features include up to 512 KB dual-bank flash, 32 KB SRAM, 8 KB data flash, with ~1 µs wake-up, and SMS (Snooze Mode Sequencer) to run LCD/touch tasks without waking the CPU. It integrates a segment LCD controller with a new VL4 reference mode that cuts LCD current by ~30% compared to the RL78/L1x. Connectivity and sensing options include UART/I²C/CSI, a temperature sensor, and an internal oscillator. With an industrial operating temperature range and a wide supply range, this MCU is suitable for induction cooktops, HVAC panels, utility meters, and battery-powered HMI devices.
Renesas RL78/L23 MCU Specifications:
- CPU core – Renesas RL78 16-bit CISC core, 3-stage pipeline, 0.03125 µs/instruction at 32 MHz
- Memory – Up to 32 KB of on-chip RAM
- Storage
- Code flash
- 64 to 128 KB (single bank)
- 256 KB (128 KB × 2 banks or a single 256-KB bank)
- 512 KB (256 KB × 2 banks or a single 512-KB bank)
- Data flash – 8 KB, 1,000,000 read/write cycles (typ.)
- Code flash
- Human Machine Interface (HMI)
- LCD Controller/Driver – 19 to 56 segment outputs, 4 to 8 commons, internal/external voltage generation options
- Capacitive Touch Sensing Unit (CTSU) – Up to 36 self-capacitance keys or 64 mutual-capacitance keys
- Peripheral I/F
- 5 to 8 channels, UART/UARTA with LIN support
- 5 to 8 channels, Simplified SPI (CSI)
- 8 to 10 channels I²C / simplified I²C
- Analog
- 8/10/12-bit ADC, 8–13 channels, internal ref (1.48 V typ.) and temperature sensor
- 8-bit DAC, 3 channels (0 to VDD)
- 1 to 2 comparators (high/low-speed modes, internal/external ref)
- Timers
- 8 × 16-bit timers
- 1 to 2 channels, 16-bit RJ timers
- 1–3 channels, 16-bit IH timers (KB40/KB41/KB42 with PWM output)
- 1 × 32-bit interval timer (or 2 × 16-bit / 4 × 8-bit)
- 4 to 8 channels, 8-bit interval timers
- RTC (1 s to 99 years, alarm, correction)
- Watchdog timer, external signal sampler, oscillation stop detector
- DMA / Event Control
- Data Transfer Controller (DTC) – normal/repeat/block modes
- Event Link Controller (ELCL) – event-based inter-peripheral signals
- Snooze Mode Sequencer (SMS) – autonomous low-power operation without CPU wakeup
- GPIOs – 40–95 pins (depending on package), N-ch open-drain (6 V / VDD level), controlled current drive pins, multi-voltage interface (1.8 V / 2.5 V / 3.0 V)
- Clock sources
- High-speed on-chip oscillator: selectable 1–64 MHz (±1% accuracy)
- Middle-speed oscillator: 1/2/4 MHz
- Low-speed oscillator: 32.768 kHz
- External main/sub clocks supported
- Misc
- RTC with alarm and correction
- Key interrupt inputs
- Clock output/buzzer output
- BCD correction circuit
- Power
- Operating Voltage – 1.6 V to 5.5 V
- Consumption – ~50 µA/MHz active, ~330 nA data retention (4 KB RAM), ~1 µs wake-up from STOP
- Power-on reset, low-voltage detectors, and Low-power modes HALT, STOP, Snooze
- Packages – 44, 48, 52, 64, 80, 100-pin LFQFP, LQFP, HWQFN (0.50–0.80 mm pitch)
- Operating Temperature – −40 °C to +105 °C (industrial grade)
The RL78/L23 is supported by Renesas’ full development ecosystem, including the e² studio and CS+ IDEs, along with Smart Configurator for peripheral setup and code generation. There’s also support for QE tools for Capacitive Touch and Segment LCD to speed up HMI design. More information about the MCU is available on the products page. The company also has an applications section on the product page where there are some “Winning Combinations” which are just pre-tested system designs that combine the MCU with other Renesas components for faster and lower-risk product development.
The company also provides two development boards: the Fast Prototyping Board (FPB-RL78L23), which is Arduino IDE-compatible for quick evaluation, and the RSSK-RL78L23 capacitive touch evaluation kit for HMI testing and validation.
Built around a Renesas R7F100LPL3CFB MCU, the FPB-RL78L23 is a low-cost development board featuring dual-bank 256KB flash, 32KB RAM, and an integrated USB-UART for programming/debugging. There is also an onboard 8×16 segment LCD and capacitive touch keys. It also offers Arduino Uno, Pmod, and Grove compatibility. The development board exposes all the MCU pins and optionally supports Wi-Fi and LoRa connectivity. The company also provides a quick start guide, user manual, schematics, BOM, application notes with sample code, design packages, and software tools for the dev board.
Also built around the same R7F100LPL3CFB MCU, the RSSK-RL78L23 capacitive touch evaluation kit supports up to 36 touch channels along with buttons, sliders, wheels, and optional LCD connectivity.
Previously, we have written about the Renesas RL78/G15, an entry-level 8-bit MCU designed for small industrial and consumer devices with 4–8 KB flash, 1 KB SRAM, and compact packages down to 3×3 mm. In comparison, the newer RL78/L23 is a 16-bit MCU that comes with various low-power features for HMI and IoT applications.
The Renesas RL78/L23 series includes 108 MCU variants in total, where the high-end models, such as the R7F100GLL3CFB#HA0, come with 512 KB flash and 32 KB RAM, and cost around $2.50 per unit for a lot of 1,500. In comparison, the entry-level MCUs like the R7F100GFH3CFP#BA0 with 64 KB flash and 16 KB RAM cost around $1.72 per unit when ordering 1,280 pieces. The FPB-RL78L23 Fast Prototyping Board costs around $37.24, and the RSSK-RL78L23 development board costs around $161.63 for a single unit on Mouser. More information is also available in the press release.
Debashis Das is a technical content writer and embedded engineer with over five years of experience in the industry. With expertise in Embedded C, PCB Design, and SEO optimization, he effectively blends difficult technical topics with clear communication
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