ON Semi RSL10 Bluetooth 5 SoC combines ultra-low power with streaming audio

ON Semi is extending its push into wireless for IoT with the announcement of the RSL10 ultra-low-power Bluetooth 5-certified system-on-chip (SoC). To be showcased at Mobile World Congress, the device is targeted squarely at IoT and mobile healthcare applications but has the added feature of being able to stream audio over Bluetooth low energy (BLE) using proprietary protocols.

BLE was not originally designed for audio streaming, having been intended to address IoT-type applications with a protocol that is optimized for short bursts versus continuous streaming. However, with Bluetooth 5’s 2-Mbit/s data rate, the bandwidth became available to apply custom protocols to enable quality audio for applications beyond hearing aids.

However, audio is processing-intensive, so with the RSL10 — ON Semiconductor’s first full BLE SoC — the company included extensive hardware-processing support. It is based on an ARM Cortex-M3 that is supported by the company’s own LPDSP32, a 32-bit dual Harvard core signal processor dedicated to executing the intensive audio codec math routines.

Around this it added 384 Kbytes of flash memory, analog and digital interfaces (GPIOs, I² C, SPI, UART), and an analog-to-digital converter (ADC) to connect to sensors.

The SoC is a full baseband controller an RF transceiver, so it needs just 10 external components to get up and running. That said, it can be implemented as part of a custom ASIC, or into a module. Packaging options are WLCSP or QFN. It supports all major Bluetooth profiles, with 36 profiles and services certified, including Rezence, for wireless charging.

With the target market of IoT and healthcare, low power is critical, so Michel De Mey, senior director of ON Semi’s Medical and Wireless Products Division, emphasized the RSL10’s current draw in deep-sleep mode: It drops to 50 nA off of a 1.25-V supply. It natively runs off of supplies ranging from 1.1 to 3.6 V, and when operating, it has a peak transmit current draw of 8.9 mA and a peak receive current draw of 5.6 mA. The receive sensitivity is –94 dBm and the transmit power ranges from –17 dBm to 6 dBm. It measures 5.5 mm² .

ON Semiconductor’s RSL10 Bluetooth 5-certified uses a 55-nm process to combine processing horsepower in a miniature, ultra-low-power SoC. (Image source: ON Semiconductor)

The design is based on BLE’s short-burst foundation, said De Mey, but with the right proprietary protocols to maintain the link, it can support full, continuous audio streaming. So while applications include fitness trackers, smart locks, and smart watches, it can also communicate with hearing aids (44-kHz audio) and eventually full stereo audio.

The RSL10 will be available in Q2 this year, and will be supported later by a development board and an IDE that includes Bluetooth protocol stacks, sample code, libraries, ARM Cortex-M3 GNU toolchain, Eclipse, and a CMSIS-Pack. A USB dongle is coming in Q3.