BQ51013 recognition delay with air core coil

The transmitter detects a receiver using an analog pin, which is a very short pulse of the transmitter coil about every 400mS.  A receiver coil will load the analog ping and reduction in amplitude will be detected by the transmitter.  It will then send a digital ping which is long pulse (10mS) at 175kHz, this will power the receiver and allow it to start the identification, configuration and power transfer phase.

But digital pin is sent automatically every 15 sec by the transmitter.  This must be what is powering up your receiver. 

It appears the coil is not placing a large enough load on the transmitter to be detected by the analog ping.

Send me coil details though the conversation option of the forum.

B/R

Bill