Austin, Texas—A group of microcontrollers (MCUs) drives power consumptions down, while targeting battery-operated wired and wireless embedded applications. The C8051F96x MCU and Si102x, Si103x wireless MCUs from Silicon Labs Inc. are well suited to designs where low power consumption is a high priority of the system, with about 65% greater run time than competing approaches. The wireless version of the basic MCU adds their EZRadioPRO sub-GHz transceiver to the single-chip design, supporting a wide range of frequencies and formats. Basic operation of the MCU requires less than 300 nA at 3.6V.
Achieving such low power required looking at three critical aspects of power dissipation and ways to reduce them: active mode power, sleep mode power, and efficiency of the battery-to-system energy transfer.
•For active mode power, the design minimizes active mode time using dedicated hardware accelerators for AES (encryption), DMA, cyclic redundancy check (CRC), SPI interface, and other functions.
•For sleep-mode power, the approach uses an ultra-low-power real-time clock (RTC), multiple RTC alarms, and enhanced LCD driver with integral charge pump.
•Finally, for active system power, an on-chip DC/DC buck converter with efficiency up to 85% is used (far better than an LDO), yet with low-enough noise performance to be viable, along with selective clock gating. The DPPE (dedicated packet processing engine) speeds RF message packet handling by a factor of five, while allowing longer sleep periods, critical to lower overall-energy use.
Since these devices target smart meters (among other applications), they include "hooks" which make them compatible with such designs and existing meter installations, such as direct interface to meter registers, and an analog front end which measures pulses and switch closures. Each MCU includes a 12-bit/16-channel ADC, current comparators, and a current reference.
Other meter-friendly features are support for Form A, Form C, and quadrature encoding from the meter transducer, along with backflow and flutter detection (which are attributes of existing meter designs), programmable pull-up resistors, dynamic self calibration, programmable switch-closure debounce, and "wake-up" on match or error conditions. Sleep current in 400 nA with the RTC running and 70 nA with the RTC disabled, from a 3V supply; wake-up time is just 2 µsec.
C8051F96x MCU block diagram
On the RF side, the Si102x/103x provide sensitivity of -121 dBm and output power of +20 dBm, using integrated LNA and PA, respectively, yielding what the vendor says is the industry's leading link budget of 141 dB, and range up to 3 km. Operating frequency can be is anywhere between 240 and 960 MHz. Included in the ICs is an antenna-diversity algorithm, as well as a FIFO, packet handler, wake-up timer, and low-battery-detection function. The wireless MCUs differ in internal processor functions which are detailed on their data sheets.
Si102x/103x block diagram
Development tools and system:Both a baseboard and MCU, as well as a wireless "picoboard" are available, and the development system is compatible with existing tools from the vendor, as part of an integrated development environment; a wireless development suite is also available. The development kit baseboard includes a multiplexed LCD driver, USB-based debug adapter, power supply, battery, cables, and documentation. Software includes code examples for the various hardware peripherals, such as DMA and management of the DC/DC converter.
Packaging, pricing, and availability: All devices are sampling now, with full production in Q1 2012. Pricing for the non-wireless C8051F96x begins at $2.41 (10,000 pieces); the wireless Si102x is $4.39 and Si103x is $3.27. Development systems and tools are also available now, priced between $199 and $299 for the non-wireless MCU and at $829 for the wireless kit.
The Si102x and Si103x are housed in a 6×8 mm, 85-pin LGA package, while the non-wireless C8051F96x is available in three package styles spanning 40 to 80 leads.
For more information on the C8051F96x, go to http://www.silabs.com/pr/lowpower; for the Si102x and Si103x, go to http://www.silabs.com/pr/wirelessmcu.