SUPPLEMENT THE INTERNET OF THINGS LESS POWER, MORE PERFORMANCE
“Low-power” and “IoT” are two of the most common words used in today’s semiconductor business, but both can mean very different things depending on the field. In some cases, the lowest power consumption is measured in nano amperes, in highly integrated designs. Minimising power consumption and the size of the overall product are necessary to make them suitable for applications like wearable electronics, activity & fitness monitors, and wireless sensors. In the end, a low-power device is always the result of careful system design and intelligent management of all components, as Fujitsu Electronics explores here
U
ltra-low power microcontrollers (MCU), such as the Apollo from
Ambiq, are taking over the essential role of executing firmware and handling the dynamic energy management of the entire application. For wearables such as fitness trackers, the MCU controls a wireless component like Bluetooth Low Energy (BLE) to communicate with a PC or smartphone. An ARM Cortex M4 core gives the
performance required to track and do fusion calculations of inertial sensors like accelerometers, gyroscopes, and magnetometers connected via I2C, SPI, or ADC. As a haptic element for alarms or notifications, a piezo or motor can be used for vibrations. The HMI can be a display with touch screen or gesture control. Different power modes for the MCU
help to scale between performance (high energy usage) and nearly no power usage. In deep-standby, the lowest power mode defined for ARM Cortex M MCUs, it is easy to achieve very low power consumption with almost any standard CMOS technology. Power consumption during operation is therefore the key concern. Ambiq Micro’s Apollo MCU family is
ultra-low power while using the company’s Micro’s SPOT (Subthreshold Power Optimised Technology). The idea behind the technology is to minimise internal core voltage to save energy. While the energy is proportional to the exposed voltage (E prop. V²), the Apollo MCU family uses about 13 times less energy. This minimises energy during high-performance mode but also in sleep modes. This series was especially designed for
ultra-low-power applications. The ARM Cortex M4 core with FPU consumes 32µA/MHz at an operation frequency of 24MHz and consumes 140nA in the deep-standby mode. For the next generation “Apollo 2” the current consumption will go down to around 10µA/MHz with an operation frequency of 48MHz. In addition to the linear low- drop voltage regulator, the company is
S6 DECEMBER/JANUARY 2017 | ELECTRONICS
Figure 1: Example for wearables like a fitness tracker
“Apollo 2” the number of peripherals will be increased and an I2S and PDM interface will be added for low-power voice recognition or keyword detection. By delivering BGA, chip-scale/flip-chip
packages and bare die, Ambiq Micro products can be used with the smallest and most highly integrated applications. Fujitsu Electronics (FEEU) not only organises product delivery and technical support on the devices itself but in addition offers advanced solutions as part of its value added distribution strategy by combining several devices into one system in package (SiP) to save on size, power, and cost. Besides the MCU, Ambiq Micro offers a
real-time clock (RTC) with optional power management with integrated low side switch as a single component, which can be used to improve the power consumption of existing applications to 22nA in RTC mode. Due to the availability in bare die format, there are many options to integrate this component into very small applications such as chip cards. Finally, the existing devices are just a
offering embedded buck converters with high efficiency. Peripherals like RTC, low frequency RC clock and high frequency RC clock also help save energy. By using an external 32KHz crystal, the high frequency RC clock can be automatically trimmed in the background.
ENERGY EFFICENCY Specially designed ADC, UART, SPI, and I2C with intelligent FIFOs help to switch off peripherals and assist the CPU in running energy efficient operations. A low leakage comparator can be coupled with the ADC inputs to handle energy efficient window functions and to wake up the MCU only if required for an ADC operation. Additional ADC features include an integrated temperature sensor, battery measurement, internal voltage reference, and switchable battery load-saving external components. For
Figure 2: Energy saving with Ambiq’s SPOT Platform
start. Moving forward Ambiq is going to announce the availability of new, additional components to their MCU product line that will increase the performance and functionality of their MCUs using their SPOT technology. With already more than 10 million delivered stand-alone RTCs and more than one million MCUs in just 6 months, Ambiq is demonstrating that SPOT is not just a theoretical possibility but a working solution!
Fujitsui Semiconductor Europe
www.fujitsu.com T: 01628 504600
Figure 3:
Block diagram for the Apollo ultra-low power MCU
/ ELECTRONICS
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