QN908x: Configuration setting for QN and WLCSP package

[ankur_rathi]

Hi,
We have designed a product using QN908x chip, by taking into consideration provided in "Hardware Design Considerations document(AN11996)".
We have two dev boards one of which uses (QN9080CHN) i.e. QFN package whereas the other board uses (QN9083DUKZ) i.e WLCSP package.
We are facing a issue in the WLCSP configured setup:
The setup which uses QFN package boots up without any issues, where as in the case of WLCSP setup most of the time boot up process get struck and it takes around 15 second to recover and start.
We tried running simple Driver example codes which was part of the SDK but the end result is the sam. Also we tried configuring the different loadcap values (set using NVDS).Note: The design and the code for both the boards are same, We are using MCUXpresso IDE (V11.0.1 [Build 2563])for developing Firmware.Is their any specific settings/configurations need to be done specifically for WLCSP package.

[ankur_rathi]

Hi Estephania,

The capacitor on Reset pin solved the issue.

[estephania_mart]

Hello,

It is good that it is solved now.

Regards ,
Estephania

[estephania_mart]

Hello,

Just to confirm, you mentioned that you are using the same design in both board, did I understand correctly ? If that is the case how are you using the same design if the devices do not have the same pin numbers and the footprint of the part is different.

Do you have a way to confirm that your device is correctly soldered and you do not have any short circuit?

Also, just as a confirmation , did you make the analog ground separated from the digital ground?

Regards,
Estephania

[ankur_rathi]

Thanks for the response Estephania.

The layout is changed wrt chip but all other things are same.

What do you mean by Analog and Digital ground. In the reference Schematic, both are connected together.
Can you explain more on that.
What is the use of 0.1uF on the Reset pin?

[estephania_mart]

Hello,

IN the same Hardware Design Consideration that you used as a base, besides the schematic you can see that there are some specific recommendations for the WLCSP package , such as the one I mentioned.

If you are using QN9083 in the WLCSP package, please, make the analog ground separated from the digital ground. It is better to separate the analog ground from the digital ground so that the digital noise does not interfere with the analog parts. For the WLCSP package, 3G, 1F, 3E, 3F, and 3D are the analog ground pins and the 4D, 4C, 5C, 5E, and 5D are the digital pins.

The capacitor you mention works as a debouncer and helps the line to have enough time to perform the reset.

Regards,

Estephania