NXQ1TXH5 Compact Charger Design

[bk2001050]

Hi Guys,

I am currently trying to design a wireless solution for a college project with this chip and would like some feedback before I get the PCB made. I have attached a schematic. 

Some info:

We are using a transmitter coil with the following characteristics:

I calculated the Capacitance Cp as dictated by the design assistance manual and the rest is identical to the EVM/application schematic. 

Couple of questions, how close do the capacitors C3, C4, C5, C6 need to be to the coil, we have mounted all the components on one side and the coil has touch pads on the other side of the pcb.

Does any 10k NTC thermistor work as a thermal sensor?

Is it a good idea to add a fuse to the input of the board as an over current protection device?

Any further thoughts/comments would be appreciated. 

[guoweisun]

HI 

For your questions please below comment:

1:

Couple of questions, how close do the capacitors C3, C4, C5, C6 need to be to the coil, we have mounted all the components on one side and the coil has touch pads on the other side of the pcb.

[gw]There are no specific references,but should be put as close as possible with coil avoid of inducting more parasitic parameters.

Does any 10k NTC thermistor work as a thermal sensor?

[gw]You can use 100K as AN11775 recommend.

[bk2001050]

Hi G.w Sun, 

Thanks for the prompt reply. The 100k thermistor was a good catch. Have you had a chance to look at the schematic, I based it on the application diagram, just wanted to make sure all was in order before getting the pcbs made.

[guoweisun]

No more issue about your schematic!

[bk2001050]

Hi G.w Sun, 

Thanks for your guidance. Quick question, the guide shows a list of coils and their corresponding R8 (Foreign object detection resistance value) but I cannot find a way to calculate this value for a different coil I am using. Is there a formula I could use or am I missing something from the datasheet here? The Tx coil I am using has the following specs:

[guoweisun]

We have a App note about FOD configuration,I will send to you!