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MCUs tout remarkable reduction in standby power at 1MHz

27 Jan 2015  | Graham Prophet

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Renesas has announced a line-up of MCUs that claims to offer higher levels of integration and a significant decrease in standby power. The company claimed that its RL78/I1D MCUs provide the lowest-available power consumption when operating at 1MHz and have a complete set of on-chip analogue peripheral functions.

RL78/I1D functions are optimised for detectors that sense minute variations in the output of sensors used to monitor for smoke, gas and motion or vibrations. The ability to use functions such as the data transfer controller (DTC), event link controller (ELC) and data operation circuit (DOC) to perform data processing and transfer, and implement long-interval timers, all without the need for CPU intervention, helps to further reduce power consumption during intermittent system operation by about 30 per cent. In the low-power operation mode, the RL78/I1D group has an operating current level that Renesas believes is much lower than that of competing products, and it wakes up from the stop-mode state very quickly. The MCU alone can make a substantial contribution to the overall power efficiency of the system.


The RL78/I1D group integrates general-purpose differential input operational amplifiers, a 12bit ADC and a comparator. This brings together on a single chip all the analogue peripheral functions required to interface with sensors.

The RL78/I1D group features a snooze mode functions that enable data processing and transfer without CPU intervention. The DTC or ELC can be used to activate sensors, activate operational amplifiers to amplify sensor signals, and transfer A/D conversion results. The DOC compares the transferred A/D conversion results and threshold values to determine whether the CPU needs to be activated. These snooze mode functions operate without CPU intervention in standby mode and reduce power consumption in products such as fire detectors, gas detectors, broken glass detectors, and security systems (human sensors).

The MCUs also allow dynamic switching between low-power operation mode and high-speed operation mode to match the system status. In low-power operation mode with a power supply voltage of 1.8V VDD 3.6V and an operating frequency of 1MHz, the operating current is only 124A (typ.). In addition, wake-up from the stop-mode state occurs in 4s (max.) when the medium-speed on-chip oscillator clock (4MHz) is used as the main system clock. This cuts power consumption during wake-up and enables the MCU on its own to contribute to the overall power efficiency of the system.

Depending on the package, there are four differential input operational amplifiers, each with two input pins and one output pin, up to 17 channels for the ADC and two analogue comparators.

The RL78/I1D group comprises 13 product versions with package pin counts ranging from 20 to 48 pins and on-chip flash memory capacities of 8, 16 and 32KB.

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