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WCT1012VLF/WCT1013VLH Consumer MP-A11 (WCT-
15W1CFFPD) V1.0 Wireless Charging Application User’s
Guide, Rev. 1, 05/2019
10
NXP Semiconductors
Figure 8. Full bridge circuits
4.6. Communication
There is bi-way communication between the EPP power transceiver and receiver. Communication from
RX to TX: The RX measures the received power and sends the information about the required power
level back to the transmitter. This message is Amplitude Modulated (AM) on the coil current and sensed
by the TX.
The RC circuits C87, R87, R88, and R92 (known as DDM) sample the signal from the coil, compress
the signal amplitude, and feed it to the ADC B-channel of the WCT1012VLF/WCT1013VLH. The
information about the current amplitude and modulated data are processed by the embedded software
routine.
Communication from TX to RX: The TX shall negotiate with the RX in the negotiation phase (if requested
by the RX). The TX uses the FSK modulation to communicate with the RX, and the communication
frequency is about 512 times the operating frequency.
4.7. FOD based on power loss
The power loss
𝑃
𝐿𝑂𝑆𝑆
, which is defined as the difference between the Transmitted Power
𝑃
𝑃𝑇
and the
Received Power
𝑃
𝑃𝑅
, i.e.
𝑃
𝐿𝑂𝑆𝑆
= 𝑃
𝑃𝑇
− 𝑃
𝑃𝑅
, provides the power absorption in foreign objects, as shown
in
Figure 9
.