Capacity and performance characterize Atmel’s megaAVR

Our ongoing coverage of Atmel’s comprehensive AVR portfolio has taken readers on a detailed MCU (microcontroller) tour this month. First, Bits & Pieces dove into the guts of Atmel’s AVR UC3 which is built around high-performance 32-bit AVR architecture and optimized for highly integrated applications.

We then spent some time with Atmel’s AVR XMEGA, an MCU designed for real-time performance, high integration and ultra-low power. And today we want to properly acquaint our readers with Atmel’s megaAVR microcontroller, which is well known for both capacity and performance.

“When your designs need some extra muscle, you need the megaAVR. Ideal for applications requiring large amounts of code, the megaAVR offers substantial program and data memories with performance up to 20 MIPS, with picoPower technology minimizing power consumption,” an Atmel engineering rep told Bits & Pieces. “All megaAVRs offer self-programmability for fast, secure, cost-effective in-circuit upgrades. You can even upgrade the flash while running your application.”

Indeed, the megaAVR family offers Atmel’s widest selection of devices in terms of memories, pin counts and peripherals. Meaning, engineers can choose from general-purpose devices to models with specialized peripherals like USB, or LCD controllers, or CAN, LIN and Power Stage Controllers.

More specifically, Atmel’s megaAVR family is equipped with on-chip flash, SRAM, internal EEPROM, SPI, TWI, USART, USB, CAN, LIN, watchdog timer, a choice of internal or external precision oscillator and general purpose I/O pins.

In terms of analog functions, the megaAVR boasts advanced analog capabilities, such as ADC, DAC, built-in temperature sensor and internal voltage reference, brown out detector, a fast analog comparator and a programmable analog gain amplifier. Simply put, the high level of integration allows designs with fewer external analog components.

And last, but certainly not least, megaAVR microcontrollers help accelerate the development process with advanced in-system programming and on-chip debug, while in-system programming works to simplify production line programming and field upgrades.

Interested in learning more? A full breakdown of our AVR portfolio is available here.

A closer look at Atmel’s picoPower technology

We briefly touched on Atmel’s picoPower technology this morning in the context of Samsung’s Galaxy S4 smartphone, which is equipped with Atmel’s sensor hub management MCU (microcontroller unit). The MCU collects and processes data from all connected sensors in real-time, optimizing multiple user experiences, such as gaming, navigation and virtual reality.

Atmel’s sensor hub MCU also lowers the overall system power consumption via picoPower technology to prevent drain and enable longer battery life. In a broader sense, it is important to note that all Atmel AVR picoPower devices are designed from the ground up for low power consumption utilizing the company’s proprietary low leakage processes and libraries to provide minimal power sipping in all sleep modes.

“An easy way to reduce power consumption in any design is to lower the operating voltage. But this would be mostly useless if analog performance was compromised,” an Atmel engineering rep told us. “Central to the AVR picoPower technology are carefully designed analog functions that continue to operate all the way down to 1.62V.”

To be sure, the various features of a microcontroller traditionally become unstable or even unusable at different voltage levels, as inaccuracies in analog peripherals, limited operation or an inability to write to non-volatile memory prevents designs from running at lower voltages. This leads to shorter battery life, larger and more expensive batteries, or a lot time spent trying to find workarounds for something that should be addressed by the microcontroller to begin with.

As such, Atmel AVR microcontrollers offer true 1.62 V operation, including all analog modules, oscillators, and flash and EEPROM programming. Meaning, various microcontroller features will not shut down one by one as the voltage drops.

“You can run the same application at different voltages without making comprises. All peripherals are available regardless of supply voltage,” the engineering rep continued. “The ADC, for example, can be used to measure the supply voltage as the cutoff voltage is approached, and when detected, it enables the application to store vital information and ensure a safe shutdown, enabling a glitch-free restart after changing batteries.”

Remember, power consumption is proportional to supply voltage, so running at as low a supply voltage as possible saves power. For battery operated devices, the Atmel AVR microcontroller can make use of the remaining power available at lower battery voltage levels as the battery depletes.

In addition to true 1.62 V operation, Atmel’s AVR peripherals with picoPower are capable of determining if incoming data requires use of the CPU or not. This feature is aptly dubbed SleepWalking, as it allows the CPU to sleep peacefully until an important event occurs, eliminating millions of false CPU wakeups. This means the CPU is no longer required to check whether or not a specific condition is present, such as an address match condition on the TWI (I2C) interface, or a sensor connected to an ADC that has exceeded a specific threshold.

Of course, entering sleep mode shuts down parts of the microcontroller to save power. Most oscillators and clocks consume a considerable amount of power when in use, and when waking up from sleep modes, these clocks need to be stable before they can be used. Waiting a long time for the clocks to be available and stable results in wasted power.

However, the Atmel AVR microcontroller is capable of waking up from sleep mode in 8 clock cycles when running from the internal RC oscillator. Moreover, a digital frequency locked loop (DFLL) replaces the traditional phase locked loop (PLL) to provide a programmable internal oscillator that is much faster and accurate.

It can also eliminate external components, which reduces the total system power consumption even more. When in sleep mode with the synchronous clocks turned off, the microcontroller can still wake up from asynchronous events such as a pin change, data received or even an I2C bus address match – enabling multiple wake-up sources from even the deepest sleep modes.

As noted above, the benefits of picoPower are clearly illustrated by Samsung’s decision to equip its flagship Galaxy S4 smartphone with Atmel’s sensor hub MCU which features picoPower tech.

“Atmel allows Galaxy S4 users the ability to enjoy applications requiring real-time motion sensing, without ever compromising battery life,” said Ingar Fredriksen, Senior Director of Flash-based Microcontrollers, Atmel Corporation. “ We look forward to teaming with Samsung on future designs.”