bq50002EVM-607+bq51013BEVM-764

How much the Z gap can reach when using the WPC1.1 receiver bq51013BEVM-764 with the WPC1.2 transmitter bq50002EVM-607?

The WPC coil to coil distance is split between the TX and RX. TX coil to interface surface is 2mm, + 0.5mm, -0.25mm (1.75mm to 2.5mm). RX coil to interface surface is 0mm to 2.5mm.

The max WPC distance coil to coil is 5mm. If the application is non-WPC and will only be used with matched TX and RX it can be increased.

Some factors will impact increased distance:
1.) Coil size will impact coupling factor and power transfer---large is better TX 50mm RX30mm to 40mm
2.) Alignment between the coils---mechanical alignment aid will help.
3.) RX coil inductance will impact system gain---higher L coil (30uH) will work better.
4.) Output power do not expect to deliver 5W at long distance – lower the better , 1W.
5.) Efficiency will be low due to low coupling factor---input power may be high.
6.) TX coil will generate a large field to overcome the distance --- higher loss in friendly metal in RX.

Start up may be a problem. System will Ping at 175kHz and this must generate enough energy at the RX Rect pin ( V-Rect) to exceed UVLO about 2.7V. Once this is done the TX will adjust operating point to support power transfer.