Smartwatch processor: Qualcomm’s Snapdragon W5+ Gen 1 for longer runtimes

With the Snapdragon Wear 5+ Gen 1, Qualcomm has introduced a new processor for smartwatches and similar wearables. The production structure, which has been reduced compared to the previous model, is intended to reduce energy consumption in conjunction with a revised hybrid mode. Thanks to the reduced space requirement, future end devices can be thinner than before or offer space for larger batteries with the same overall height.

Like the Snapdragon Wear 4100+ presented in 2020, the Snapdragon Wear 5+ Gen 1 uses a hybrid architecture. The actual system-on-chip (SoC) again has four ARM Cortex-A53 CPU cores. The one-gigahertz graphics unit, dubbed the A702, is new to previous Snapdragon Wear models; the Wear 4100+ uses a 320MHz A540. The production takes place in 4 nm. With the Wear 4100+, which is used in the Fossil Gen 6 watches, among other things, it is 12 nm. The SoC area is reduced accordingly from 128 mm2 to 90 mm2, the height of 0.69 mm to 0.48 mm – while doubling the performance at the same time.

More powerful co-processor

Qualcomm has completely revised the co-processor known as AON (always-on). Its structure width is reduced from 28 nm to 22 nm, the previously used ARM Cortex-M50 gives way to a Cortex-M55. The clock rate increases from 50 MHz to 250 MHz. As with the Wear 4100+, the co-processor is responsible for connecting the sensors – such as the heart rate and accelerometer – as well as for the display in standby. What is new, however, is the option of having the co-processor handle audio playback and control in standby. The same applies to notifications. Another innovation is the U55 machine learning core integrated in the co-processor.

Qualcomm has retained the division into SoC and co-processor introduced with the Snapdragon Wear 3100 in 2018 with the Snapdragon W5+ Gen 1.

The revised hybrid architecture should contribute to lower energy requirements. The Bluetooth module is part of the co-processor, so the SoC can still be put into sleep mode if there is a corresponding connection. Another example: Only a few areas of the SoC and the co-processor are active when recording fitness and location data as well as simultaneous audio playback – a typical jogging scenario.

The revised hybrid architecture makes it possible to leave large parts of the system on standby in certain use cases.

According to Qualcomm, this leads to lower energy consumption compared to the Snapdragon Wear 4100+ in many scenarios: 36 percent for music playback via Bluetooth, 42 percent for GPS positioning and in pure standby. Overall, this should lead to a 50 percent increase in runtime – assuming that the smartwatch is in active mode for 5 percent of the day. According to Qualcomm, the expected runtime improvements are a reason why the SoC uses the Cortex-A53 cores and none of the successors – A55 or A510. When asked, it was said that the newer cores are more powerful, but not as economical in the areas prioritized by Qualcomm.

Snapdragon W5 Gen 1

Qualcomm also introduced the Snapdragon W5 Gen 1 (without +). Only the co-processor is missing compared to the Plus model. This variant of the processor is intended for special areas, including wearables for children, seniors, healthcare and devices for the Chinese market.

The Snapdragon W5+ Gen 1 is designed for use with Wear OS 3.0 or Android or AOSP (Android Open Source Project). On the other hand, FreeRTOS is used on the AON co-processor.

First models from Mobvoi and Oppo

The first smartwatches with the new processors should be available in stores from late summer 2022. Mobvoi is equipping the upcoming top model of the next TicWatch generation with the Snapdragon W5+ Gen 1 and Wear OS. Oppo, on the other hand, relies on the Snapdragon W5 Gen 1 and AOSP in the Oppo Watch 3. The Pixel Watch planned for autumn 2022, on the other hand, should use a different processor.

Compal (left) and Pegatron offer the first smartwatch reference designs based on the Snapdragon W5+ Gen 1.

Altogether, according to Qualcomm, different companies are already working on 25 different models. The first reference models designed to reduce development costs come from Compal (Wear OS) and Pegatron (AOSP). (pbe)

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