"Always-on is certainly not the main culprit, but if implemented poorly, it can reduce battery life by perhaps 10%," Gwennap said. "The goal for future devices is to reduce the battery impact [of always-on features] to 2% or less."
Moto X isn't the only mobile device leveraging the power of DSP for always-on capabilities, he said. "Both iPhone 5S and Galaxy S4/S5 have sensor hubs that are always on. But they do not include voice activation, like Moto X." Qualcomm and Audience are using DSP for always-on functions. "For wearable devices that don't have a voice interface, MCU sensor hub is an OK solution, but DSP is required for voice." The advantage of Ceva's always-on solution is that "it is licensable and can be used in custom chips for wearable devices."
To illustrate how its DSP could lower power consumption, Ceva offered the example of a smartwatch with a microphone, camera, and motion sensors. Gwennap said the DSP in the smartphone "can continuously listen for a voice trigger, continuously watch for a face, continuously monitor the sensors, and control the BLE link with a remote device. It can also perform simple updates to the display, such as maintaining the correct time."
Briman told EE Times the DSP consumes 0.15 mW on average to perform all these functions.
Along with its TakeLite-4 DSP, Ceva offers a host of software modules and firmware that can run concurrently on a single core. They include Bluetooth 4.1 (Classic and Low Energy), always-on functionality (voice trigger, face detection, etc.), HD audio playback and post-processing, voice communication, noise reduction, sensor fusion (context awareness), and Android Multimedia Framework (AMF). The architecture supports the offloading of various processing elements from the CPU to the DSP under an Android OS (including KitKat).
Ceva expects "user-centric IoT" devices (designed to interface with a human) using TeakLite-4 DSP to emerge on the market by the end of this year or in early 2015.
— Junko Yoshida, Chief International Correspondent, EE Times