Low-energy MCU with touch sensing in chip-scale package

August 21, 2015 // By Graham Prophet
Giving them the collective name “Sleepy Bee”, Silicon labs has introduced the EFM8SB1 microcontrollers, 8-bit devices intended for ultra-low-power, small-footprint IoT applications with capacitive touch sensing requirements.

EFM8SB1 Sleepy Bee MCUs, available in a 1.78 x 1.66 mm wafer-level chip-scale package (WLCSP), are presented as the industry’s smallest MCUs – one-quarter the size of 8-bit MCUs in conventional QFN packages. These MCUs are aimed at touch-based, battery-powered and space-constrained IoT and industrial applications requiring long battery lifetimes and energy-efficient human interfaces. Target applications include wearables, remote controls, Bluetooth accessories and eReaders, as well as industrial automation, home automation and office equipment.

The EFM8SB1 Sleepy Bee MCUs are Silicon Labs’ most “energy-friendly” 8-bit devices offering sleep mode power (50 nA with full memory retention and brown-out detection) and 2 µsec wake-up time. Core speeds scale up to 25 MHz, and flash sizes range from 2 kB to 8 kB. The MCUs also integrate a capacitive sense controller offering an ultra-low-power, under 1 µA, wake-on-touch capability and 12 robust capacitive touch channels, eliminating the need for on/off switches in many space-sensitive products such as wearables.

Silicon Labs supports touch-sense interface design with its Capacitive Sense Library available within the Simplicity Studio development platform. Simplicity Studio provides firmware designers with production-ready firmware, from scanning buttons to filtering noise. By using the Simplicity Studio Capacitive Sense Profiler to visualise real-time data and the noise levels of cap-sense buttons, developers can easily customise touch and no-touch thresholds and noise filtering settings, greatly simplifying the addition of capacitive touch to IoT applications.

The EFM8SB1 MCUs offer a mix of analogue and digital peripherals including a high-resolution capacitance-to-digital converter (CDC), a 12-bit analogue-to-digital converter (ADC), high-performance timers, and enhanced SPI, I²C and UART serial ports. These and other analogue/mixed-signal peripherals are all configurable and accessible to developers through Silicon Labs’ crossbar technology.

In a WLCSP package, EFM8SB1 MCUs are priced at $0.47 (10,000). The EFM8SB Sleepy Bee starter kit is priced at $29.

Silicon labs; www.silabs.com/EFM8