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Holtek BP45F0044 Application Note

Wireless electric toothbrush
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BP45F0044 Wireless Electric Toothbrush Application Note
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.
AN0569EN V1.00
1 / 8
November 23, 2020

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Summary of Contents for Holtek BP45F0044

  • Page 1 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.

  • Page 2: Operating Principles

    BP45F0044 Wireless Electric Toothbrush Application Note Figure 1. Charging Base Application Circuit Operating Principles 1. Charging base coil: Inductance: 32.01µH Type: cylindrical, 8mm in height, 10mm in diameter, with magnetic column 2. Toothbrush coil: Inductance: 53.59µH Type: cylindrical, 9mm in height, 15mm in diameter, without magnetic column 3.

  • Page 3: Hardware Description

    Holtek. The demodulation block diagram of the BP45F0044 device is shown in Figure 4. The OPA will be configured to operate in the non-inverted mode, where S0 and S3 are on and S1 and S2 are off.

  • Page 4: Software Description

    Before the charging base implements demodulation, the Rx terminal should be prepared with the corresponding settings. In the toothbrush terminal program provided by Holtek, 2 bytes of data is used as the toothbrush ID code and 1 byte of data is used as the user-defined data. Users can find the following parameters in the my_define.h file in the toothbrush program of the...
  • Page 5 However, the component errors in the coil or sampling resistor must be taken into account. To resolve this, Holtek has devised a way to make the DAC adaptive to ensure that for each demodulation, the DAC can output a central value of the sinusoidal waveform, which the CMP can compare to allow the MCU to correctly demodulate the waveform.
  • Page 6 BP45F0044 Wireless Electric Toothbrush Application Note  Toothbrush ID Identification The Holtek wireless rechargeable electric toothbrush solution provides users with a complete and convenient ID identification function. At the same time, it can also adjust the PWM operating time, Ping interval time, toothbrush not-present time and other parameter settings. It also allows the toothbrush to have a customised 8-bit data capacity, where users can have data transmission for information such as toothbrush status, battery voltage etc.

  • Page 7: Reference Material

     Charging Base Flow Chart After adjusting the above parameters, the charging base subroutine call flow is shown in the accompanying figure. This flow has been implemented in the program provided by Holtek, which users can use directly without changing the flow.

  • Page 8: Limitation Of Liability

    Information displayed at such sites. Hyperlinks to other websites are at your own risk. Limitation of Liability In no event shall Holtek Limited be liable to any other party for any loss or damage whatsoever or howsoever caused directly or indirectly in connection with your access to or use of this website, the content thereon or any goods, materials or services.

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