The extensive family of Renesas RL78 microcontrollers consists of both general-purpose devices and application-specific MCUs. These increasingly popular MCUs make ultra-low-power applications possible by giving system designers advanced power-saving features and high-performance operation.
RL78’s Low-power Modes Maximize Battery Life
- Three low-power modes maximize battery life by either putting on-chip functions such as the CPU, clock and peripherals in standby or by turning them off when they aren’t being used.
- In Run mode, RL78 devices offer substantial savings in current consumed when compared to competitors.
- Halt mode disables CPU operation, saving as much as 80% of total MCU current, while allowing a fast CPU wake-up time.
- Stop mode achieves the lowest RL78 power consumption; it disables the CPU and on-chip functions that run on the CPU clock.
- Some peripherals (ADC, UART and SPI) remain operational in Standby modes.
- MCU transits from Stop mode to Snooze mode by timer trigger or serial data reception.
- MCU wakes up only when acquired data matches the condition. If not, go back to Stop mode without CPU intervention.
- Power savings up to 76% can be obtained; e.g., the ADC consumes 1.2mA in Snooze mode vs. 5.1mA in 32MHz Run mode.
Wide operating range without sacrificing efficiency
- RL78 MCUs have widest operating voltage in their class: 1.6V to 5.5V.
- Built-in voltage regulator allows RL78-based systems to operate from a 5.0V with the same power consumption over the voltage range.
RL78 MCUs have versatile power-down modes and main and subsystem (32kHz) clock options.
- Peripheral functions available in Standby mode consume miniscule current:
– 12-bit interval timer (0.02μA)
– RTC (0.02μA)
– WDT (0.02μA)
– 15kHz on-chip oscillator (0.20μA)
– 32 kHz oscillator (0.24μA)
– LVD (0.08μA)
- RAM data is retained in all MCU modes.
- ADC, UART and SPI can be active in Snooze mode.
- In Halt mode, system can wait for ADC end or serial transfer end, followed by a quick (0.3 μs) wake-up.
|Peripherals (Main system clock)||■||■||■ ADC, UART/SPI|
|Peripherals (32kHz clock)||■||■||■||■|
|RTC + 32kHz oscillator||■||■||■||■||■|
|12-bit interval timer (Optional peripheral, 0.02μA)||■||■||■||■||■||■|
|LVD (Optional peripheral, 0.08μA)||■||■||■||■||■||■|
|WDT + 15kHz oscillator (Optional peripheral, 0.22μA)||■||■||■||■||■||■|
|Power consumption w/o peripherals and optional peripherals unless otherwise specified||4.6mA (32MHz) 2.1mA (32MHz)1 1.2mA (8MHz)||0.54mA (32MHz) 0.26 mA (8MHz)||1.2mA (32MHz, ADC) 0.7mA (32MHz, UART/SPI)||0.49μA||0.49μA||0.23μA|
|Wake-up time 2||0.3μsec (32MHz) 1.2μsec (8MHz)||5μsec||122μsec||18μsec||18μsec|
Notes 1: NOP Instruction 2: Min. time All the power consumptions listed above are typical value examples of RL78/G13 (64KB)