BP45F0044 Wireless Electric Toothbrush Application Note
AN0569EN V1.00
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November 23, 2020
BP45F0044 Wireless Electric Toothbrush
Application Note
D/N: AN0569EN
Introduction
Wireless rechargeable toothbrushes are divided into two main parts, a wireless charging transmitter
(Tx) and a sonic electric toothbrush (Rx). Communication between these two parts is one-way from
the toothbrush to the charging base. Holtek provides the charging base communication function,
which can enable the charging base to receive toothbrush status, ID, toothbrush presence, etc. The
communication principle is based on AM load modulation. The toothbrush terminal uses a resistor
and a transistor to control the load to change the current. When the charging base receives these
changes in current, it can then implement communication using the integrated OCP, CMP and
demodulation algorithm after RC filtering.
This application note describes the transmitter communication demodulation and how to use the
Holtek Library to implement wireless electric toothbrush communication.
Functional Description
The charging base hardware design is shown in Figure 1. In the initial standby state, the charging
base will Ping transmitting power to the toothbrush at regular intervals. If the toothbrush receives
a Ping action, the charging base will demodulate the returned code. If the ID code is correct, the
charging base will then continuously transmit power to charge the toothbrush. During this period,
the toothbrush will send back its ID code to indicate the toothbrush presence at regular time
intervals. Holtek has integrated the parameters that users will encounter into the program and has
provided related subroutines for the user to call. Users can quickly adjust these parameters and
implement an ID identification function according to this application note.
