Hello Natanael,
Please see the answers below embedded in your text...
We are trying to develop a new product that will implement wireless charging technology and we are trying to follow the guidelines noted in the Qi specification. We have our eyes set on the NXQ1TXH5 controller.
There are some considerations for this design and we would like to receive some input to know if what we are trying to achieve is actually possible while still being eligible to opt for the Qi certification, you see we are very short on space and the coils used in "Part 4: Reference Designs" of the Qi Specification may be a little too thick for our requirements.
>> Apart from the requirements in "Part 4: Reference Designs" your charger must also pass an interoperability test with previously certtified products. As soon as you start deviating from the reference designs you will get more trouble passing this interoperability test.
We want to know, first, if using a custom coil with a thickness of no more than 2.3 mm (including shielding) will be enough to supply 7.5 W with at least a 65% efficiency?
>> The NXQ1TXH5 is suited to supply 5W at the output of the receiver. It will not be able to supply 7.5W to the output of the receiver.
Second, we are going to be embedding the coil in a PCB cutout, so the coil will be surrounded by PCB which in turn has components mounted on it, including the wireless charging controller, a micro-controller and the rest of passive components, will that have a negative effect in the operation of any of these components?
>> When you place metal (copper traces, components) in the vicinity of the transmitter coil then there is the risk that the magnetic field induces voltages in the traces resulting in losses.
These losses will be noticed by the transmitter in the same way as losses due to a coin between the transmitter and receiver. So the Foreign Object Detection might be triggered earlier.
And third, the interface surface will be around 0.1 mm thick, is that enough?
>> I assume that you refer to the distance between the primary coil and the interface surface. This distance should be about 2mm. If you make it 0.1mm, then it might work but it is not a Qi-charger. When you make the distance between the primary coil and secondary coil smaller, then the efficiency goes up, but the maximum transferable power will reduce.
Best regards,
Tomas
