02/2018 • www.ECNmag.com
Figure 1: System overview.
By Horst Gether, Product Manager for ACI and ANC with ams AG; Martin Denda, Staff Application Engineer ACI and ANC with ams AG
Challenges in True Wireless
Battery life and communication with chargers are key factors for improving wireless headsets.
The audio market for wireless Bluetooth headsets is growing rapidly. People have gotten used to wireless
audio systems, while the mobile phone industry is pushing
toward a world without audio connectors and cables.
Most of the average users who think about Bluetooth
audio, picture clumsy over-the-ear headsets with very
little extra functionality. However, the trend for modern
audio systems goes toward physical miniaturization,
while maximizing the functionality and user experience.
This demand leads to a new audio category called True
Wireless Headsets (TWS headsets). At first glance, these
new in-ear systems look like rather simple devices, but as
you can imagine, the devil is in the details. TWS systems
do require a lot of electronics to be smart and user-friendly, as the high-level system overview illustrated in
Figure 1 shows.
When thinking about TWS headsets in daily use, there
are several ways to enhance the customer experience
and hassle-free user interface integration. One of the
main issues TWS system designers are facing is playtime,
because battery space is usually very limited in these
headphones. Typical battery sizes of 60–150 mA/h can
be reached, which results in a playtime of 2–4 hours.
Once the battery goes flat, the earbud needs to get a fresh
charge before being ready for its next mission.
Currently, the most advanced TWS headphones
are shipped with a cradle rather than having a wire
connected to each of the earpieces for charging the
batteries. The cradle acts as a handy compartment,
In order to help a standard TWS headset be smart
and user-friendly, a key requirement is the possibility to
exchange data between charger cradle and earbuds. If
the cradle knows the battery status, it can automatically
start recharging the earbuds. This continuous recharging
process is necessary due to the quiescent current
consumption caused by the always-on Microcontroller
Unit (MCU) as shown in Figure 2. Vice-versa, if the
earbud knows about an empty charging cradle, it can
automatically inform the user via Bluetooth notification to
charge the device’s battery.
In terms of automatic start-up and pairing, a smart
connection would also be beneficial. If the cradle informs
the earpiece that the compartment lid has opened,
they can wake from their sleep mode and prepare the
Bluetooth pairing process rather than pressing a button on
the earbuds to enable the devices.
Besides the enhanced user experience, a link between
cradle and earbud could enable better industrial design,
software updates, personalization of earbuds (name, EQ
data), and transfer of music data, to name just a few
application examples of a feature-rich and differentiating
product in the market.
To get a clearer picture about the technical
implementation, let’s dig deeper and have a look at the
system in more detail, as shown in Figure 2.