--- title: "W55RP20-EVB-PICO + WIZPoE-S1 = Magic Smoke" url: "https://maker.wiznet.io/forum/15852" markdown_url: "https://maker.wiznet.io/forum/15852/md" type: "Forum topic" category: "MCU & Boards" author: "irukard" created: "2025-08-27T01:52:29+09:00" last_activity: "2025-09-05T08:18:52+09:00" language: "en" views: 12 replies: 7 source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)" --- # W55RP20-EVB-PICO + WIZPoE-S1 = Magic Smoke ## Question Asked by irukard on 2025-08-27 in MCU & Boards. Hi! I naively assumed that WIZPoE-S1 is a perfect non-isolated match for W55RP20-EVB-PICO. After programming, I unplugged USB, put WIZPoE-S1 in female headers (VC1/VC2 on RJ45 jack). I connected this combo to TP-Link TL-SG2008P (802.3at/af) and after 2 seconds and successfully power and Ethernet negotiation W5500 chiplet released magic smoke trough small hole in chip package (2 mm left from "W" in W55RP20 marking). Surprisingly RP2040 chiplet works normally. After removing WIZPoE-S1 I can program it via USB, UART, I²C works normally. No obvious problems. But W5500 does not work. Probably magic smoke was a very crucial component of this chip. I tested this with another pair W55RP20-EVB-PICO + WIZPoE-S1. The result was exactly the same. - 2pcs of W55RP20-EVB-PICO were purchased in Botland (https://botland.com.pl/) - 2 pcs of WIZPoE-S1 were purchased in Mouser What may be important W55RP20-EVB-PICO boards were soldered to PCB with all GND fields connected via PCB's ground plane. Tell me please. What went wrong? ## Replies ### Reply 1 by irukard, 2025-08-27 Dear AI bot. You understand nothing. I'm not frustrated. Just disappointed. ### Reply 2 by irukard, 2025-08-27 Now I've got 4 pcs of killed W55RP20-EVB-PICO, but I've also got answers. In all modules SGM62112-3.3 died. VSYS is shorted to GND. On oscilloscope I confirmed that WIZPoE-S1 on start generate long voltage spike (about 1 second) up to 10-12V. This is way over SGM's absolute maximum rating, which is 6V. Long story short that kills SGM regulator. Do not use W55RP20-EVB-PICO with WIZPoE-S1. Wiznet - now you owe me some boards. ### Reply 3 by Alan, 2025-08-27 (in reply to reply 2) Sorry. We are well aware of this matter. How can we assist you? Shall we send you new boards? Please kindly provide the details to the following email: **Alan@wiznet.io** Thank you. ### Reply 4 by irukard, 2025-08-27 (in reply to reply 2) Alan: I wasted a way too much time developing solution based on W55RP20-EVB-PICO and WIZPoE-S1 thinking that it will be compatible. My main constraint is time not money. If I would know that your PoE solution is garbage I would pick ESP32-POE from Olimex. You want to be maker community friendly? This is what should you do: 1. Don't publicly admit that you are well aware of this matter and you did nothing to prevent that. You will have to deal with mob of angry people. 2. Update the documentation of W55RP20-EVB-PICO and WIZPoE-S1 and inform people that right now those products are not compatible. This one line would save me a ton on time, effort and money. 3. Develop PoE module that does not create sudden voltage spikes on power up and power down. It does not need to be efficient. 4. Use TVS to protect sensitive components. Yes. Main 3.3V voltage regulator is kind of important. Adding TVS triggering on 5.5V on VSYS line sound like a good option. How can you assist me? I got all my code and PCB done. Now I need to figure out what should I do to make it work. I need 5V (4.5-5V) to power on Sensirion SEN55. So my only option is VSYS. But VSYS from WIZPoE-S1 spikes to 10-12V on power on, and about 8-9V on RJ45 jack disconnect. Do you have any ideas how to mitigate that? Should I add some load, TVS and LDO? Also I would appreciate WIZPoE-S1 schematics to figure out how to modify this module. ### Reply 5 by Alan, 2025-08-28 (in reply to reply 2) I acknowledge everything you said. I sincerely apologize. We are aware that there is an issue with the WIZPoE-S1. Therefore, we plan to discontinue the WIZPoE-S1. The WIZPoE-P1 is fully compatible. Would you like to resolve the issue while still using the WIZPoE-S1? If you are planning mass production, we recommend switching to the WIZPoE-P1. Unfortunately, we are unable to share the circuit schematics. ### Reply 6 by irukard, 2025-08-31 (in reply to reply 2) Hi Alan, It is too bad you are unable to share the schematics of WIZPoE-S1. It really would help us with debugging. Our team found the way how to ad-hoc modify this module, to a point it can be used with W55RP20-EVB-PICO without or risk of damaging the board. It is far from perfect but without schematics and values of capacitors and resistors in feedback loop, we are not willing to invest more time to further improve it. Right now feedback loop is too sluggish, it should react way faster. Maybe it was a victim of BOM optimization and some values were changed. **Here is what we recommend:** - **Add 100Ω load resistor** increase minimal load of the module (we just piggy-backed 3 x 300Ω in paralel to ceramic caps). Seems that no-load sleep mode mentioned in SD4954B datasheet does not guarantee nice output voltage. - Replace 47µF electrolytic output capacitor to **330µF/10V/ESR 17mΩ**. - **Add 5.6V Zener diode** on output (we used **BZV55C5V6**). Since we could not find any TVS for such a low voltage, and SGM62112-3.3 has absolute maximum input supply voltage at 6V, this was a good cheap option, to cut down the short voltage spikes. Hope this information helps everyone with similar problems. So in conclusion: - We fried 4pcs of W55RP20-EVB-PICO, I will mail you. If you could provide new boards I would appreciate that. - Cumulatively we spend about 10h on debugging and testing WIZPoE-S1, because right now we are out of time, and this prototype series must be operational and provide measurement data. - Our trust in Wiznet products was totally destroyed. Sorry, but WIZPoE-S1 should never reached the market. And after discovering the problems it should be recalled or at least the documentation updated to indicate problems with hat module. Being responsible builds trust. In electronics mistakes happens. How you deal with them matters, especially in maker community. - For the test run we will use W55RP20-EVB-PICO with modified WIZPoE-S1. - For the long run, we will probably develop our or PoE module. Something safe, efficient, EMI compliant, not necessarily cheap. ### Reply 7 by Alan, 2025-09-05 (in reply to reply 2) WIZPoE-S1 was discontinued shortly after its release due to identified issues. However, since many units had already been sold to resellers, we were unable to recall the shipped products. As you can see, we do not sell WIZPoE-S1 anywhere on our site. We regret the cost and time you’ve spent. If you send us your module, we will review it. If you can trust us once again, please contact us via email. We can recommend another PoE module that complies with EMI regulations and offers stable operation. --- Source: https://maker.wiznet.io/forum/15852