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Bluetoooth Low Energy & Low Power Solutions

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The expected IoT market of 30+ Billion connected devices will largely be dominated by either WiFi, Zigbee or Bluetooth (Low Energy) based solutions. With so many connected devices there are multiple reasons to reduce the energy consumption per device. In most cases this is related to battery life requirements but the energy required from the mains power should not be ignored either. The challenge at hand is to develop systems and products which use the energy as effectively as possible.

The basis to low power designs are low power integrated circuits. With a focus in this article on Bluetooth Low Energy which is developed for low power point-to-point communication with mobile devices. The BTLE 4.1 standard itself can be used where the relatively energy hungry BT 2.0 and 3.0 are not an option. Typical applications are beacons that run for years on a single coin cell, wearables and devices powered by alternative energy sources. There are a number of factors that greatly influence the efficiency of a device. These are transmit and receive power, wake-up and return to sleep timing and of course power usage in low power sleep modes. These numbers also influence the average advertising consumption; the most common activity for a Bluetooth Low Energy device.

Developing a connected device means using power optimized solutions for the host microcontroller and for the communication interface. Which controller and Bluetooth device are used depends of course on the use case and system requirements. Atmel supports a number of different architectures from Bluetooth devices with external microcontroller to single chip integrated solutions with or without external flash. Atmel's ATBLC1000 is a single chip ultra low power Bluetooth device:

Key ATBTLC1000 features are:

  • Operating voltage: 1.8V to 4.3V
  • sub-1µA sleep current
  • sub-3mA / 4mA TX/RX current (@3.6V, 0dBm Pout).
  • Ultra small chipscale package of 2.26x2.14 mm and 4x4 mm QFN options

To support easy evaluation and development of your Bluetooth solution, Atmel offers the BTLC1000 XPLAINED starter kit. This kit is a hardware platform based on the ATBTLC1000-MR110CA module together with the ultra low power Atmel Cortex M0+ L21 hosted Xplained Pro evaluation board. The combination of these two boards integrates with Atmel Studio and facilitates software development and power measurements to be done through the development environment. These specifications easily extending battery life 2x to 4x.

The SAM L21 is the first device in its Cortex M0+ based ULP (Ultra-Low Power) family utilizing Atmel’s proprietary     picoPower® technology.  Already sampling, the device will go into mass production at the end of October 2015.   It is available in flash memory densities of 32KB, 64KB, 128KB and 256KB and in a wide range of package options and pin counts.   Also recently announced in August was the SAM L22 sister device which contains a 320 segment LCD Controller and this will go into mass production in December 2015.   The SAM L21 can support the following current consumption numbers:

  • Sleep Current - 200nA
  • Standby Current with RAM retention and RTC - 0.9uA
  • Active Current - 35uA/MHz running EEMBC CoreMark

Atmel's ultra-low power SAM L21 family is ideal for a variety of low power applications including Internet of Things (IoT), consumer, industrial, medical and other battery-powered devices. The low-power innovations in this Atmel | SMART family is achieved through several technological breakthroughs including:

Best-in-class active mode current consumption.

  • SRAM back biasing to reduce leakage in sleep modes.
  • Sleep modes that do not only gate away the clock signal to stop switching consumption, but also remove power from sub-domains to fully eliminate leakage.
  • SAM L21 peripherals that support Sleepwalking—a technology that enables peripherals to request a clock when needed to wake-up from sleep modes and perform tasks without having to power up the CPU Flash and other support systems.
  • Atmel's proprietary Event System that allows peripherals to work together to solve complex tasks using minimal gates and also the lowest possible power.
  • Ultra-low power capacitive touch sensing peripheral that can run in all operating modes and supports wake-up on touch.

While running the EEMBC® ULPBench™, the industry marker for low power, the SAM L21 achieved a score of 185, the highest publicly recorded score for any Cortex-M based processor or MCU in the world – and higher than the 167 and 123 scores announced by other vendors.

The following links provide more information on the devices detailed in this knowledge item:

Bluetooth: http://www.atmel.com/tools/atbtlc1000-xstk.aspx

SAML21 microcontroller: http://www.atmel.com/products/microcontrollers/arm/sam-l.aspx

 

 

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