NXP-NCI_LPC82X_example default to CFG1 or CFG2?

[benjaminchang]

Hi,

We are the first time running "NXP-NCI_LPC82X_example" without any change to the source code, with OM13071 LPCXpresso824-MAX board + OM5578 (PN7150).

It worked well in the beginning and tags read ok. But somewhat after plugin/out the USB cable several times, we found the IC cover became very hot, and finally it cannot work anymore. LPC board can still run, but PN7150 cannot be found anymore. We just do not know what happened and wonder why?

We followed AN11990 to connect both demo board, for Vbat and Vant,

From "OM5578_PN7150S-schematics", we can see this connection is for CFG2.

From UM10936,

But after checking the project code, we found the default setting is for CFG1 in nfc_settings.h

#define NXP_TVDD_CONF        1 // 1=CFG1, 2=CFG2

Again From UM10936, for the different connection of CFG1,

Our questions are,

- Should we change the setting to CFG2 instead?

 If yes, we suggest making a note in the related document such as AN11990.

- What is the impact of this "SW setting=CFG1", but "HW connection=CFG2" issue?

 Is it just a performance issue as Vbat1 is for TXLDO input? Does this relate to our IC damaged? 

 Please note the IC was good and working in the beginning.

Regards,

Benjamin

[Kan_Li]

Hi Benjamin,

Thanks for the reporting! I am checking with the expert team for this issue, and will let you know when I have any more information.

Thanks for your patience!

Have a great day,
Kan

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[benjaminchang]

Hi Kan,

Thanks for your help. Still, we are waiting for the reply!

Now we replaced the damaged PN7150 chip with a new one. We didn't change the H/W, so it is still the CFG2 connection. But we connect the single 3.3V to both Vbat1 & Vbat2. So theoretically it is a CFG1 connection. Now it works.

Still, we are hoping to have your comment.

Thanks,

Benjamin

[Kan_Li · Accepted solution]

Hi Benjamin,

I just got the info from the expert team, please refer to the following for details.

This configuration is allowed by PN7150, even if not efficient in term of RF performance. TVDD will be referenced at 3.0V while the input is at 5V (reference is 4.75V in CFG2) implying dissipation which could explain the IC going a bit hot … but in no case it should damage the IC. PN7150 is designed to support such dissipation which is commonly used in some specific design.

Hope that helps,

Have a great day,
Kan

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[benjaminchang]

Thank you!