Feature: RF


The CPU’s capabilities as a whole require careful review, too. Questions include whether it has enough resource capabilities for the application processing tasks, in addition to running software stacks


Selecting the best Bluetooth Low Energy SoCs


By Emmanuel Sambuis, Senior Marketing Director, IoT Home and Consumer Products, Silicon Labs


B


luetooth Low Energy (BLE) continues to be the wireless protocol of choice for many short- range connectivity applications. A popular method of connecting battery-powered peripheral accessories such as headphones, smart speakers and fitness trackers, Bluetooth


system-on-chip (SoC) ICs are a must-have component in many connected product designs. However, while the Bluetooth wireless SoC may appear to be


a commodity purchase, the reality is far from it. Determining the target power consumption of any battery-powered device


28 February 2021 www.electronicsworld.co.uk


is a critical aspect of any design, whether for a consumer electronics product or an industrial IoT sensor. For the embedded design team, understanding the real-world


power budget requirements of a product go far beyond the power consumption figures quoted in a semiconductor’s supplier’s data sheet. Te selection process requires sufficient time to thoroughly review the data sheets of short-listed SoCs. Tis stage should also include acquiring a good understanding how the SoC operates, during both active and sleep modes, so that power consumption can be minimised for extended battery life. What might appear a relatively straightforward task can turn


into an all-encompassing exercise as the designer conducts deeper analysis of SoC datasheets. A good starting point is to investigate the actual current consumption in the SoC’s active receive and transmit modes. Typically, these will be a few milliamps, with the transmit mode the more current- hungry of the two. For example, the Silicon Labs EFR32BG22 SoC has a receive current of 2.6mA, and during transmit at 0dBm, 3.5mA. Note that these figures are just for the wireless transceiver, not the complete SoC. A common mistake when calculating the power budget is to consider only the receiver’s power consumption, not the entire SoC. For the EFR32BG22, overall current drain during receive is 3.6mA, and 4.1mA whilst transmitting. The CPU consumption characteristics, commonly quoted


relative to the clock speed in microamps per megahertz, also need investigation. The CPU’s capabilities as a whole require careful review, too. Questions include whether it has enough resource capabilities for the application processing tasks, in addition to running software stacks. Best-case figures quoted on the front page of the data sheet usually relate to the processor running at its maximum clock frequency. However, does the data sheet include figures of consumption when it is running at a slower clock rate, for example?


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