Since there is no direct electrical feedback from the load (system output) to the power transmitter, the power
receiver must establish communication with the power transmitter to provide this feedback instead.
To match load requirements and prevent excessive power transmission, the power receiver communicates to the
power transmitter the required power level using amplitude shift keying (ASK). This is done by the receiver
modulating the amount of power that it draws from the power signal. The transmitter detects this as a modulation
of the voltage across and/or current through the transmitting coil and adjusts its operating conditions accordingly.
The power transmitter can communicate to the receiver as well, this time using frequency shift keying (FSK). This
is done by the power transmitter directly modulating the power signal. Communication in this direction enables
proprietary communication.
STWBC86 supports proprietary packet FSK reply on proprietary ASK packets from Rx. This feature is requiring
control from the external host MCU on Tx side and details can be found in dedicated Application Note about
bidirectional communication between STWLC38 and STWBC86.
UM3161
Bidirectional communication
UM3161 - Rev 1
page 34/78
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