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WCT1012VLF/WCT1013VLH Consumer MP-A11 (WCT-
15W1CFFPD) V1.0 Wireless Charging Application User’s
Guide, Rev. 1, 05/2019
14
NXP Semiconductors
Figure 11. Resonance signal
The circuit for the free-resonance Q measurement is as shown in the following figure, which samples the
signal on resonance capacitors.
Figure 12. Free-resonance Q measurement circuit
Pre-FOD based on the Q factor
The pre-FOD serves to detect foreign objects without an RX. The TX uses analog ping to detect objects.
If an object is detected, a digital ping is initiated to decide if it is an RX. If the object is a metal FO, it is
heated by a digital ping. The TX provides a pre-FOD method based on the Q factor to detect the foreign
object and prevent it from being heated before the transfer is initiated.
4.9. Analog sensing
Some ports of the ADC A-channel of the WCT1012VLF/WCT1013VLH are used to sense analog
signals, such as the temperature, full-bridge input current, input voltage, and rail voltage.