Communication Interfaces

• UART: 5 channels, supporting automatic baud rate, infrared modulation and UART wake-up.

• I2C: 1 channel.

• SPI: 1 channel.

• ISO 7816: up to 2 channels.

• LVD Voltage Detection: monitors internal chip power supply voltage and external input voltage.

• Two comparators CMP1 and CMP2 for external voltage detection.

General Features

• High Integration: Integrated 32-bit ARM Cortex-M0 core, Σ-Δ ADC, SAR ADC, metering module, LCD driver (RN7213), timers and multi-channel PWM, hardware temperature-compensated RTC, EEPROM, etc.

• Wide Voltage Range: Measurement accuracy guaranteed from 2.8V to 5.5V.

• Typical operating voltage range for CPU minimal system: 2.2V ~ 5.5V.

• GPIO supports connection with devices of different operating voltages.

• High Performance: Maximum CPU operating frequency up to 29.4912 MHz.

• High Precision: Active energy error less than 0.1% within 5000:1 dynamic range.

• Typical temperature coefficient of metering reference: 5ppm/℃.

• RTC second pulse error less than ±5ppm at -25℃ ~ 70℃; minimum calibration resolution: 0.068ppm.

• Package:RN7211: LQFP64, suitable for LED meter;RN7213: LQFP100, suitable for LCD meter.

Processor

• ARM Cortex-M0 core.

• Max operating frequency: 29.4812 MHz.

• 128KB Flash, 100,000 erase/write cycles, data retention over 20 years.

• 16KB SRAM.

• 32KB EEPROM, 1,000,000 erase/write cycles, byte-level operation supported, data retention over 20 years.

• Single-cycle 32bit×32bit multiplier.

• 2 DMA controllers.

• Integrated hardware watchdog.

• Complete integrated software and hardware development environment provided.

Measurement & Metering

• 3-channel Σ-Δ ADC with instantaneous sampling output.

• Typical reference voltage temperature coefficient: 5ppm/℃ (max 15ppm/℃).

• 3-channel RMS value output; error less than 0.2% within 2000:1 dynamic range.

• 2-channel active, reactive and apparent power measurement; error less than 0.1% within 2000:1 dynamic range.

• Update rate of RMS and power parameters: 13.982Hz.

• 2-channel instantaneous active and reactive power, update rate up to 7.2KHz.

• 2-channel active, reactive and apparent energy metering; active energy error < 0.1% within 5000:1 dynamic range.

• 2-channel power factor measurement, error < 0.2%.

• Line frequency measurement, error < 0.02%.

• Phase angle detection for 2 current channels and 2 voltage channels.

• 3-channel peak detection function.

• Voltage sag detection supported.

• Sampling channel gain, power gain, phase calibration, power and RMS offset calibration available.

• Automatic DC offset correction function.

LCD Driver (RN7213 Only)

• Supports 4×34, 6×32, 8×30 display modes.

• DMA automatic display rotation without CPU intervention.

• Built-in charge pump for LCD driving voltage; clear display over wide voltage and full temperature range.

• Automatic display rotation power consumption lower than 20μA.

Timers

• 2 × 32-bit extended timers: interval timing, square wave output, external/internal event counting, single pulse output, 4-channel PWM output, pulse width measurement.

• 2 RTC timers.

• 1 Cortex-M0 built-in system timer.

SAR ADC

• 10-bit SAR ADC, time-division multiplexed with temperature sensor and up to 5 analog input pins.

RTC (RN7213 Only)

• Automatic hardware temperature compensation; second pulse error < ±5ppm at -25℃ ~ 70℃, minimum calibration resolution 0.068ppm, meeting national standard accuracy and power consumption requirements.

• Built-in temperature sensor; measurement accuracy ±1℃ within -25℃ ~ 70℃.

• Power consumption lower than 2μA.

Other Peripherals

• High-speed GPIO, compatible with peripheral devices of different voltage levels.

• Up to 8 multiplexed key interrupt pins.

• Up to 7 multiplexed external interrupt pins.

Product Overview

RN721X is a highly integrated, high-precision, high-reliability and low-power electric metering SOC chip. It integrates a 32-bit ARM Cortex-M0 core, 3-channel Σ-Δ ADC, metering module, multiplexed SAR ADC, LCD driver (RN7213), timers, multi-channel PWM, temperature sensor, hardware temperature-compensated RTC, EEPROM, UART/SPI/I2C/ISO 7816 communication interfaces, GPIO and interrupt controllers, fully meeting functional and performance requirements of various smart electric measuring instruments.

RN721X enables flexible single-phase anti-tampering energy meter solutions, and its wide dynamic range adapts to shunt-based wide-range meter designs.

It is suitable for the development of various single-phase parameter meters, three-phase voltmeter & ammeter, DC meters and more.

Combined with Renergy three-phase metering chip RN7302, it forms a cost-effective chipset for three-phase multi-function meters, multi-rate meters, harmonic meters and residual current fire detectors.

RN721X includes two models:RN7211 in LQFP64 compact package for LED display meters;RN7213 in LQFP100 package for LCD display meters.