NXP20P0477 || Moisture Sensor || Abnormal Behavior

[JyotiVaishnav]

Hi NXP Team, 

We're using the NXP20P0477 IC on our board, and we're encountering an issue with its abnormal behavior. Even when no fault is present, it sometimes incorrectly shows a fault, and the FLAG signal goes low. At Controller end we are not using CC2 IC it is NM 

Please check the below Moisture IC schematic FYR

[JyotiVaishnav]

Hell Tomas,

One more query i need to address here , the marking on the IC which we are using in our current project is N7710022934 ,and the marking on the ic which we used in our previous project (were Ic is working properly , no false moisture detection)is N775911z234.
Why there is different marking in the IC ?, we have used same part no .

Please help us to answer this query , i just want to cross check whether there is no issue in the IC itself .

[TomasVaverka]

Hi Jyoti,

I am still waiting for feedback from our product/test group, in the meantime could you please place the known-good (N775911z234) IC onto a board where the current lot shows false detection? If it works fine, the issue is definitely IC batch-related.

Also, could you please try to tie CC2 to GND through a pull-down resistor? 

BRs, Tomas

[JyotiVaishnav]

Hi Tomas, 

The 1kΩ pull-down resistor is specified on the CC2 line. Do you have any recommendations for the pull-down resistor value? Please share your input if there are any suggested values. Also, please see the image below. Meanwhile will check after changing the IC 

[JyotiVaishnav]

Hi,

Is there any difference in any of the LOT/BATCH CODE, please find the details below for both the LOT code mentioned below 

We are currently using this one and it is not working 

And in our previous project we have used below part - and it is working fine 

Please check and provide us the details for the LOT/BATCH code difference. 

[JyotiVaishnav]

Hi Tomas, 

Awaiting your response, our activities are blocked because of this.

Please check and provide the feedback. 

[TomasVaverka]

Hi Joyti,

The only feedback I have received so far from our product/test group is that "N775911z234" corresponds to WW34 of 2019 and "N7710022934" to WW34 of 2022. I am still waiting to hear if there are any functional differences between them or if there is any known issue with this newer batch (N7710022934).

BRs, Tomas

[JyotiVaishnav]

Hi Tomas, 

We are waiting your response here, please check and help us to debug the issue on an urgent a basis.

[TomasVaverka]

Hi Jyoti,

Sorry for the delay in getting back to you, I have been out of the office the last few days. I will look into this with our product engineer later today and get back to you ASAP.

BRs, Tomas

[JyotiVaishnav]

Hi Tomas, 

We are waiting for your reply. 

We have measured the waveforms on the some of the test points, the detailed description is provided in the below attached document. Please refer the link to open the document. 

FTP Link : https://ftpa.vvdntech.com/nextcloud/index.php/s/X3oxcsfAdXSSSEa

Password : e3PaWy78Ao

[TomasVaverka]

Hi Jyoti,

Thank you for sharing additional details. I was able to download your presentation and will look into it with the product engineer soon.

BRs, Tomas

[TomasVaverka]

Hi Jyoti,

FLAGB is an open-drain output and your schematic correctly uses a 100kOhm pull-up to 3.3V. It goes low when the device enters Moisture.DET state (COMP2 = high and COMP3 = low).

CP_EN is pulled-up to 3.3V via a 4.7kOhm resistor which enables the moisture detection logic.

Any noise or improper line status on CON_CCx can cause transitions into Moisture.DET state, especially during attach/detach events. So check for connector or routing noise that might mimic moisture. Also consider logging or probing CON_CC1/CC2 and CC1/CC2 voltages during failure.

BRs, Tomas

[JyotiVaishnav]

Hi Tomas, 

Please find the below waveform - measured on CC1 (IC input TP148)and FLAG (TP154 flag pin) in charging condition

below waveform - measured on CC1 (IC input TP148)and FLAG (TP154 flag pin) in moisture fault condition

Observation: As seen in the image above, a 350mV drift was observed on the CC line under fault conditions, and a moisture fault occurred after 4.3ms.

Please provide your suggestion to debug the issue