Warning: long post.
As part of a pcb, I have a W5500 circuit. As far as I know, I have followed all recommendations in the datasheet, the hardware guide, and other best practices (like advice given in thread in this very forum).
However, for some reason, the W5500 chip dies. Sometimes it takes a while (I had one prototype pcb working for about a week before the W5500 died, another prototype lasted about a day) and sometimes it dies quickly.
So I have been populating some prototype pcbs with only the W5500 circuit, and powering it with 3.3V directly from a lab power supply. It doesn’t help, the W5500 chip still dies. The W5500 part of the schematic is this
I have also tried a minimal version of the W5500 circuit (basically just the two capacitors that the W5500 needs and the decoupling capacitors). Nope, the W5500 still dies. The minimal schematic is this
Component values are on the schematic, if anything is unclear, feel free to ask for more info.
I hand solder the prototypes.
The pcb is 4 layers, the stackup is top layer, ground plane, inner signal layer, bottom layer. The relevant parts of the pcb is shown in these pictures:
inner signal layer
I have verified the components (values, package size and other data), the footprints against the datasheet, the reference schematic and the wiz550io schematic and pcb.
I have checked the gerber files for errors - none found. I have also had a couple of colleagues double check my work - they couldn’t find any issues either.
I have verified that the pcb is ok - no shorts between 3.3V and ground, between pads or otherwise suspicious measurements.
On the long surviving prototypes I measured the voltages (3.3V in, VDD digital and analog on the W5500) they are stable and within specifications.
On the W5500 only or W5500 minimal only prototypes the symptoms are that current draw rises quickly to about 130 - 135 mA and sometime after that the W5500 chip dies.
How do I know that the W5500 chip dies? I measure the resistance between 3.3V input and ground on a populated prototype pcb before applying power to it, it is in the kilo-ohm range. after the W5500 has dies, the measurement is just a few hundred ohms. If the W5500 chip is the desoldered, the measurement goes back to kilo-ohm range again.
Obviously something must be wrong with my schematic or pcb layout, but so far we (my colleagues and I) haven’t been able to find it.
Any advice would be great. Thanks.