topic Re: LPC5460X USB1_VDD short circuit to GND in LPC Microcontrollers

LPC5460X USB1_VDD short circuit to GND

yanqinghe — Wed, 24 Oct 2018 03:54:06 GMT

Dear NXP:

We designed our LPC5460X board refer to NXP EVB, it works good at first, but after hot swapping and hot insertion several times, the CHIP USB1_AVDDTX3V3 and USB1_AVDDC3V3 are short circuit to GND, do you know what operation could cause this problem ? (If don't supply USB1_AVDDTX and USB1_AVDDC3V3, the MCU software still can run)

Best Regards

Yan

Re: LPC5460X USB1_VDD short circuit to GND

kerryzhou — Thu, 25 Oct 2018 06:50:27 GMT

Hi Yanqinghe,

How you design your circuit in AVDDTX3V3?

This is the official board schematic, you can refer to it, and compare it with yours:

Besides, about the solder, do you use the soldering flux? In my memory, some not good soldering flux may solder the pins after some time power on.

So, you'd need to use the specific water to clean the board after you solder it, this is my own experience.

Have a great day,
Kerry

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Re: LPC5460X USB1_VDD short circuit to GND

yanqinghe — Thu, 25 Oct 2018 10:38:59 GMT

Hi Kerry

Thanks for your reply, I think it's not solder problems ;I connect the USB1_VBUS directly from connector, like the follows picture.

MCU_VCC_3V3 is generated by a LDO(input is VBUS);

I saw the LPC546X datasheet suggested USB interface solutions as the follow picture shows, it has some restriction for USB_VBUS, I'm not sure if this cause the problem :

Is this the reason USB1_AVDDTX3V3 and USB1_AVDDC3V3 are short circuit to GND after hot swapping and hot insertion several times ?

BestRegards

Yan

Re: LPC5460X USB1_VDD short circuit to GND

kerryzhou — Mon, 29 Oct 2018 09:10:49 GMT

Hi yangqinghe,

From your schematic, your USB1_VDDTX3V3 and USB1_AVDDC3V3 already from the LDO, not from the VBUS directly, it should not have the problem about the VDD power slow than the USB_VDDTX3V3.

I checked your method with the lpcxpresso LPC54608 board, the official board use two different LDO in MCU VDD and USB VDD, so, do you try to hot plug the official board, whether it have problem on your side or not? It seems still somewhere hardware circuit have problems.

Have a great day,
Kerry

Re: LPC5460X USB1_VDD short circuit to GND

yanqinghe — Mon, 29 Oct 2018 09:22:24 GMT

Hi Kerry：

I can't reproduce the problem on official board throw hot plug the official board; There's more than one board have this problem, I don't know what cause this problems.

BestRegards

Yan

Re: LPC5460X USB1_VDD short circuit to GND

kerryzhou — Tue, 30 Oct 2018 09:25:34 GMT

Hi Yan,

After the pin is connect to ground, whether it is connected to ground forever, if you put it for about one day, then check these two pin, whether it is not connect to ground or not?

I just want to make sure, the pin is damaged forever or just the temperature phenomena.

Wish it helps you!

Have a great day,
Kerry