--- title: "W5500 RSVD pins - connect to GND or leave floating?" url: "https://maker.wiznet.io/forum/14762" markdown_url: "https://maker.wiznet.io/forum/14762/md" type: "Forum topic" category: "Ethernet Chips" author: "kewgal" created: "2023-01-04T12:22:35+09:00" last_activity: "2023-01-06T06:05:50+09:00" language: "en" views: 646 replies: 5 source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)" --- # W5500 RSVD pins - connect to GND or leave floating? ## Question Asked by kewgal on 2023-01-04 in Ethernet Chips. Hi. I saw that there is difference between application note and datasheet of W5500. What should I do with RSVD pins? There is schematic where each RSVD pin is floating (application note) [docs.wiznet.io](https://docs.wiznet.io/img/products/w5500/w5500_sch_v110_use_mag_.pdf) ### [w5500_sch_v110_use_mag_.pdf](https://docs.wiznet.io/img/products/w5500/w5500_sch_v110_use_mag_.pdf) 44.02 KB In datasheet there is information that 23 RSVD Pull-down I It must be tied to GND and Rest sould be floating. There is W5500 devboard where each RSVD is connected to GND via 10k resistor. [docs.wiznet.io](https://docs.wiznet.io/img/products/w5500/w5500_evb/w5500_evb_v1.0_140527.pdf) ### [w5500_evb_v1.0_140527.pdf](https://docs.wiznet.io/img/products/w5500/w5500_evb/w5500_evb_v1.0_140527.pdf) 63.69 KB What should I do? ## Replies ### Reply 1 by Eugeny, 2023-01-04 These pins are already having internal pull-downs averaging at 85k. Thus the question is are these internal pull-downs enough and why some circuits have external pull-downs, and some not? ### Reply 2 by kewgal, 2023-01-04 (in reply to reply 1) Eugeny: > Thus the question is are these internal pull-downs enough and why some circuits have external pull-downs, and some not? Yes, i saw that here are pulldowns at RSVD pins. So when RSVD should have external pull down? ### Reply 3 by Eugeny, 2023-01-04 No idea. We must wait for WIZnet R&D to advise. If you need to make a design right now, just leave seats for those resistors, and will decide if to populate them or not later. ### Reply 4 by kewgal, 2023-01-04 Eugeny: > u need to make a design right now, just leave seats for those resistors, and will decide if to po Thanks Eugeny. So we will wait ![:slight_smile:](https://emoji.discourse-cdn.com/twitter/slight_smile.png?v=12) ### Reply 5 by jaden, 2023-01-06 Hi kewgal As Eugeny said, W5500 RSVD pin has internal pull-down(thanks Eugeny!). The internal pull-down resistance value of 85K is too large and can be swayed by external noise. That’s why we used an external pull-down resistance of about 10K. Reset pin is internal pull-up but as the same reason with RVSD pin, it can be use with external pull-up. Thanks! --- Source: https://maker.wiznet.io/forum/14762