8-bit, 8051-based MCUs come with high-accuracy analogue peripherals

November 20, 2015 // By Graham Prophet
Silicon Labs' EFM8LB1 “Laser Bee” micrcontroller family offers speed, Accuracy, cost-saving integration and small footprint for optical modules – the company presents the devices as having the highest analogue performance and peripheral integration in the 8-bit market.

They combine a high-speed ADC, multiple DACs, a highly accurate temperature sensor, two comparators and a 72 MHz 8051 core with up to 64 kB of flash. They are packaged in 3 x 3 mm QFN, for space-constrained, performance-intensive applications such as optical modules, test and measurement instrumentation, industrial control equipment and smart sensors.

Silicon Labs suggests using them in high-speed, analogue-intensive optical transceiver modules in telecom and data communications. Optical module applications require small-form-factor MCUs offering analogue performance and integration. Laser Bee MCUs integrate up to four 12-bit DACs, eliminating the need for four external DACs typically required by optical modules.

The on-chip 14-bit, 900 ksample/sec ADC includes an input sequencer and direct memory access (DMA) controller, enabling raw data collection without MCU intervention. This capability frees the MCU for other tasks, providing an increase in overall system performance while enabling the MCU to enter a low-power mode for energy-saving benefits. The MCU's 72 MHz pipelined 8051-based 8-bit core can execute more than 70% of instructions in 1 to 2 clock cycles, satisfying the processing needs of high-speed optical modules and other computationally intensive applications.

EFM8LB1 MCUs integrate four configurable logic units (CLUs), enabling designers to implement combinational logic and/or synchronisers without using external components. Claimed as the smallest CLU implementation, the logic units support a variety of digital functions such as replacing system glue logic, generating special waveforms or synchronising system event triggers. Each CLU is completely programmable, to interface Laser Bee MCUs with other chips in the system. By reducing the component count and PCB space required to support glue logic, the logic units ultimately minimise BOM cost and time to market.

Many precision analogue applications include sensors or other components that require temperature compensation. For example, laser drivers and other components in optical modules are sensitive to temperature variations. Laser Bee MCUs have a built-in, factory-calibrated ±3°C accuracy temperature sensor, enabling very accurate temperature measurement without