(iTers News)  - What most matter in the design of IoT, or Internet of Things and wearable devices are power consumption and security.

For example, what users of Apple Watch feel the most uncomfortable with is that they have to recharge them almost every day.

Mostly, a CPU is a power guzzler, as the constant wake-up from static, or sleep mode and active run-up of data-intensive apps consumes lots of power quickly draining the battery power.       

To make CPU as power efficient as possible, Freescale Semiconductor adopts a computational-task partitioning design scheme between two cores, taking a cue from ARM Holdings' big.LITTLE CPU design concept     

Its recently-taped out i.MX 7 Series comes built with two different heterogeneous ARM cores - 1GHz Cortex-A7 and 266MHz Cortex-M4 -in what the chip maker says is the industry’s most power efficient applications processor.

The high-performance, but power-guzzling Cortex-A7 processor mainly perform computational-heavy tasks like Web browsing and video and image rendering, Meanwhile, the power-thrift Cortex-M series performs relatively light duties like.

"The ARM Cortex-M4 is a sort of MCU that runs on duty-light RTOS, or real time OS, while Cortex-A7 runs on full-scale Linux and Android OS, which consumes more power. For most of the running time, the Cortex-M4 usually prevails performing usual duty-light task at a low voltage, but when on demand for duty-heavy complicated tasks, the Cortex-A7 wakes up to do that computational cycle-guzzling tasks, " said Michael C. Kim, senior manager with Freescale Semiconductor Korea, Inc.   

"The multi-OS system also helps to enhance security features, as crucial information can be programmed on Cortex-M3 core, " added he                   

The Cortex-A7 and Cortex-M4 boasts of processor core efficiency levels of 100 μW /MHz and 70 μW /MHz respectively.

All of the cores can be individually power-charged to perform different tasks depending on demand.  This performance-on-demand chip architecture allows the i.MX 7 series to meet bursty, high-performance tasks like running Linux, graphical user interfaces, wireless stacks or other bandwidth-rich data transfers with one or both of Cortex-A7 cores.

Balancing acts

When high levels of processing are not needed, the work can be transferred to the smaller, lower powered Cortex-M4, enabling the power gating of the Cortex-A7 core.

The balancing act helps to reduce the power consumption of the i.MX 7 series CPU. For example, the i.MX 7 series boasts of core power efficiency of 15.7 DMIPS/mW, a new Low Power State Retention mode (LPSR) of 250 μW, a 48% power savings, compared with other competing product.

On top of that power-saving computational cycle split design scheme. the i.MX series come embedded with its new companion PF3000 PMIC, or power management IC. allowing it to intelligently manage power consumption.

The PF3000 PMIC is specifically  developed and optimized to be used with i.MX 7 series to provide the highest possible overall system power efficiency.

With up to four buck converters, six linear regulators, RTC supply, and coin-cell charger, the PF3000 is engineered to support all specified i.MX 7 use cases and conditions.

"The PMIC can manage a variety of voltage requirements depending each system blocks' demand," Kim said.      

The PF3000 PMIC is a fully integrated solution enabling system-level power efficiency by optimizing power delivery not just to the processor, but also to peripherals and various types of system memory resources in an overall component solution size of less than 100mm^2.

The PMIC supports one-time programmable memory for controlling startup sequence and output voltages with no external components required.  Best in class light load efficiency combined with user programmable Standby, Sleep/LPSR, and Off power modes maximize the i.MX 7 industry leading low power performance. 

Multi-OS suuport  

Coming built into multiple i.MX 7 reference designs and featuring a single price point extensible across multiple cores, operating frequencies and memory types, the PMIC also helps streamline development and lower overall bill of materials costs.

Target applications vary from wearable and IoT devices, secure point-of-sale, or POS equipment, smart home controls, industrial devices like ESS, or electricity storage system. The i.MX 7 series will also address e-Readers market when it come embedded with an advanced, fourth-generation EPD controller.

The first members of the series are i.MX 7Solo and the i.MX 7Dual product families. Both of the two applications processor are built with a 28nm ultra low power-leakage process technology.

They also support DDR self-refresh mode, GPIO wakeup, and memory state retention.

“Freescale’s i.MX 7 series scores industry leading dynamic and static power efficiency numbers, at a fraction of competing devices,” said Ron Martino, vice president of Applications Processors and Advanced Technology Adoption for Freescale’s MCU group.

“We’ve combined our ultra-low power performance-on-demand architecture and the ARM Cortex-A7 – the most energy efficient ARM processor ever developed – to deliver innovative new features like a new battery savings mode consuming only 250μW, representing a 3x improvement that minimizes wake up times without requiring Linux reboot, ” added he.

Highly secure 

High bandwidth connections are provided through a variety of interfaces such as PCIe and Dual Gigabit Ethernet with AVB support. Both of the new i.MX 7 processors support the performance and power driven range of external memories including eMMC5.0 and LowPower-DDR3, meeting higher bandwidth applications.

As wearable and IoT devices stay connected to the Internet around-the-clock, security protection is also hot issue.  To address increasingly stringent security requirements for Point-of-Sale and IoT applications, i.MX 7 series integrate Elliptic Curve Cryptography technology, active tamper detection, secure boot and other hardware-enabled features that help to secure sensitive information.

In addition, the i.MX 7 architecture features independently controlled and secured resource domains, which partition to isolate security threats and enable a hardware firewall.

The temper detection is a security protection technology that immediately erase codes stored in a memory stack or black out the memory system when hackers break into the memory stack to hack codes. "Hackers usually tear down POS, for example, to crack open its memory system to hack codes programmed there. And, then, they analyzes the code to hack other POS of the same brand.  That's where the Temper plays out to the effect, " said Michael C. Kim, senior manager with Freescale Semiconductor Korea, Inc.   

The i.MX 7 series support multiple OSes like Linux, Android, and other RTOS, or real time OS.

Samples of the i.MX 7Solo and i.MX 7Dual applications processors are available now, whit volume production scheduled for November 2015.

The PF3000 PMIC is available righ now. Two PF3000 board designs are available now: the KITPF3000FRDMEVM evaluation board and the KITPF3000FRDMPGM programming board.