W5500 died after few minutes

[asdf557f]

Hi, guys.

So, I have hardware-related question.
Currently I developing the board with W5500. Circuit is the same as in reference design. Differences are:

• SI-60062-F used for RJ-45 with magnetics
• 10nf as series capacitors in RD+/RD-
• by mistake I mounted 13k bias resistor instead of 12.4k at EXRES1 pin.

After power on the chip starts normally. Firmware initialization done ok. But after few minutes of operation suddenly W5500 died completely. Now when reading data via SPI, the MISO signal is always 0. At TOCAP and 1V2O measured voltage circa 1.7V. No sign of overheat before and after though.

So, my question is whether the 13k resistor at EXRES1 can be the cause. Or any other ideas?
Thanks for any input

[alexpescaru]

I don’t think it’s because of the resistor.
By mistake, we put 110K instead. The chip refused to work, even if the oscillation at crystal pins was OK.
As soon as the correct resistor was put, the chip came to life.

Can you change the chip to see if it’s dead or not?

[midnightcow]

Hi,

EXRES1 resistor is used in analog vias voltage in PHY of W5500.
You’d better keep the value recommended by WIZnet.

Thank you.

[asdf557f]

So today I performed one more test at different board. That time with recommended resistor 12.4k.
I decided not mount the RJ-45 connector for a while.
After first power on, all voltages were ok. I ran the firmware, was able to read chip ID, initialize and come to link checking loop.
Then after few minutes I measured 1V2O again and it became +3.1V instead of 1.2V initially, which is far from normal operation in my opinion.
Ok, I proceed further. Mount the RJ-45, and then even got correct link status via firmware.
BUT, after 10-15 minutes of normal operation, first the link came down and then SPI died silently.
That’s the story.

I had double checked circuit and PCB, and still wonder what the reason is.

The question. The 1V2O pin is the output of some sort of LDO. Thus if I connect only pins +3V3, +3V3A and GND, then I should get 1.2V at 1V2O pin? or some additinal components needed for that? I just want check minimal possible circuit.

[kzl108]

Hi!

The question. The 1V2O pin is the output of some sort of LDO. Thus if I connect only pins +3V3, +3V3A and GND, then I should get 1.2V at 1V2O pin? or some additinal components needed for that?

The LDO needs external capacitor to supply stable power.
So there should be 10nF capacitor between the 1V2O and GND.
And there should be 4.7uF capacitor between the TOCAP and GND.

You can refer to the W5500 Reference schematic. (I attached some related part.)
Here is the link for schematic.
wizwiki.net/wiki/doku.php?id=pro … fschematic

Thank you!

[asdf557f]

kzl108, alexpescaru, midnightcow
Thank you all for the help! So lucky to find such friendly community.
I gonna buy more chips at next week and W550io as working reference device.
Then I’ll let you know about my solution. Hopefully