PN7150B0HN/C11002Y Vdd(tx) waveform question

[bob_zhang]

Our customer use PN7150 and find Vdd(tx) there is a pull down after remove NFC card. They want to make sure if it is a normal phenomenon.

[Kan_Li]

Hi @bob_zhang ,

No , it is not a normal phenomenon. Did your customer get this waveform from their custom board? Did they follow the app note of https://www.nxp.com/docs/en/application-note/AN11756.pdf ?

Please kindly clarify.

Have a great day,
Kan

-------------------------------------------------------------------------------
Note:
- If this post answers your question, please click the "Mark Correct" button. Thank you!
- We are following threads for 7 weeks after the last post, later replies are ignored
Please open a new thread and refer to the closed one, if you have a related question at a later point in time.
-------------------------------------------------------------------------------

[bob_zhang]

Besides，Customer test voltage of 7150 when the device power off. The result is VDD（MID）=0.844V，VDD=1.8V，VDD(TX)=2.49V,meanwhile VEN=0V，VDD（PAD）=0V，VBAT=3.6V. It looks like PN7150 internal LDO is on default. Is this right?

[Kan_Li]

Hi @bob_zhang ,

What does " the device power off" mean here with VBAT=3.6V? Seems PN7150 is in standby mode as VDD(TX) is around 2.5V. Please kindly refer to the following for more details.

Have a great day,
Kan

-------------------------------------------------------------------------------
Note:
- If this post answers your question, please click the "Mark Correct" button. Thank you!
- We are following threads for 7 weeks after the last post, later replies are ignored
Please open a new thread and refer to the closed one, if you have a related question at a later point in time.
-------------------------------------------------------------------------------

[bob_zhang]

Hi Kan，

   Because the device is a pad. "Power off" Means the pad turn off. But Vbat is still present. Customer mainly focus on Vdd(tx) instantly  pull down to 0.8V  issue after remove card.

[Kan_Li]

Hi @bob_zhang ,

Thanks for the clarification! For the NFC antenna design on the custom board, is it a symmetric tuning? How about the Q factor? Did your customer follow the app note of AN11755? Please kindly clarify.

Thanks for your patience!

Have a great day,
Kan

-------------------------------------------------------------------------------
Note:
- If this post answers your question, please click the "Mark Correct" button. Thank you!
- We are following threads for 7 weeks after the last post, later replies are ignored
Please open a new thread and refer to the closed one, if you have a related question at a later point in time.
-------------------------------------------------------------------------------

[bob_zhang]

Hi Kan，

    Thanks for your quickly feedback.

    Yes,It test on customer board and we don't have demo board to check. Customer refered AN11756 When schematic and layout design.I want to know if this issue is only related to power circuit design. What is the probably reason? We are checking according to AN11756.And schematic show as attchment file.

[Kan_Li]

Hi @bob_zhang ,

Thanks for the information! For C715 and C716 's position,  is C715 close to Vbat pin and C716 close to Vbat2 pin? Please kindly clarify.

Have a great day,
Kan

-------------------------------------------------------------------------------
Note:
- If this post answers your question, please click the "Mark Correct" button. Thank you!
- We are following threads for 7 weeks after the last post, later replies are ignored
Please open a new thread and refer to the closed one, if you have a related question at a later point in time.
-------------------------------------------------------------------------------

[bob_zhang]

Hi Kan，

         We checked C715 and C716's position.C715 and C716 are both close to pin12/13(Vbat2/Vbat1). Customer add a 4.7uF at pin26(Vbat) and test again. The result is same as before.Customer served layout file as attached file. More suggetion for this ?