The Tiny Cortex-M0+ Just Got Smaller
Freescale's Kinetis KL02 microcontroller is only 1.9mm by 2mm (Fig. 1). The tiny Cortex-M0+ processor is ideal for ultra-small application from ingestible healthcare sensing systems to mobile devices. The chip includes a 12-bit ADC making the system ideal for sensing applications.
The processor runs at 48 MHz delivering 15.9 Coremarks/mA. It has 10 power modes to help developers conserve power and to provide a flexible power on environment. It can use as little as 50µA/MHz. It has a low power boot mode that minimizes power spikes when booting or starting from a deep sleep. This helps in battery applications where peak current may be limited. The processor can wake up in 4µs. It needs 1.71 to 3.6 V to run.
The microcontroller (Fig. 2) runs a 2-stage pipeline with single cycle GPIO instructions. It contains 32 Kbytes of flash and 4 Kbytes of RAM. That is pretty hefty for such a small device. The flash is based on Freescale's 90nm, low-leakage TFS technology. It is tied to a zero-wait state memory controller.
In addition to the 10-channel, 12-bit DAC, there is a high speed analog comparator. The chip can run off an internal clock or low cost, external crystal. The communication support includes a UART, SPI, and a pair of I2C ports. The bit manipulation engine makes management of peripherals and peripheral data more efficient. A peripheral crossbar switch allows flexible pin assignment in software.
Many of the peripherals are smart allowing them to function while the processor is in deep sleep mode. The peripherals can often perform actions without waking up the processor thereby minimizing power consumption.
The Kinetis KL02's small size is possible because of Freescale's wafer-level chip-scale packaging (Fig. 3). The solder balls provide direct connections between the PCB and the die. There are no additional bond wires or interposer connections. This actually increases durability in harsh and rugged applications. The approach also minimizes die to PCB inductance and improves the thermal characteristics of the system.
The small chip size opens up design possibilities not available to other form factors such as QFN, LQFP and BGA. This might include a pill for health care sensing applications. It also makes the chip ideal for portable consumer devices and wearable devices.
The Cortex-M0+ architecture has significant advantages and one is the plethora of programming tools available from Freescale and third parties. The developer tools from Freescale include the Eclipse-based, CodeWarrior IDE and software generation tools like Processor Expert. The MQX RTOS is part of the package and it can be tailored for the smaller memory footprint of the KL02. KL02 boards for Freescale's Tower development platform are available.
Debugging is often a chore with smaller chips. The KL02 addresses this with a micro trace buffer available to the debugging tools.
This is one impressive package. Most tiny microcontrollers tend to be pin limited or function limited with RAM that is often measured in tens of bytes. Those are useful but the KL02 is going to be the one that designers will want. It is likely to find a home in everything from lighting to robotics to health care.
