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Introduction

STWBC86 is primarily a wireless power transmitter that provides up to 5W of power.

It offers the most flexible and efficient solution for controlling the power transfer to a receiver (RX) in applications

such as smart phones, smart wearable, hearable devices that use electromagnetic induction for recharging.

The 32-bit core MCU is the supervisor of the whole device and manages all the functional blocks to

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establish and maintain communication with the receiver,

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optimize the efficiency by properly adjusting the operating point

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guarantee reliability by monitoring and protecting both the load and the device itself.

The Tx is responsible for controlling the transmitting coil and generating correct amount of power requested by

the Rx.

Transferring a correct amount of power ensures the highest level of end to-end efficiency due to reduced energy

losses. It also helps maintaining a lower operational temperature.

The I2C interface provides access to the internal registers of the STWBC86 for applications in which the host

system directly monitors or controls the power transfer.

The Tx can adapt to the amount of energy transferred by the coil by adjusting the frequency, duty cycle of the

PWM voltage on the transmitting coil.

The power transmitter firmware is placed in ROM and is able to operate fully autonomously. This firmware is

patchable with 8kB on-board FTP.

STWBC86 comes with a current limit and over-temperature protections to ensure safety of the device.

Figure below shows a block diagram of the device with simplified interconnections among the functional blocks.

The inverter converts the DC input voltage into an AC voltage, which is used to drive the coil. The four switches

of the inverter (essentially an H-bridge) are controlled by the digital core in order to minimize both conduction and

switching losses.

Two bootstrap capacitors are externally connected to the BOOT1-BOOT2 pins to correctly drive the high-side

switches of the inverter.

VIN power supply is also the input rail for auxiliary linear regulators in charge of deriving the 5 V and 1.8 V supply

voltages.

STWBC86

Introduction

DS14079 - Rev 1

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