Electrical – LAN9500AI (USB to Ethernet IC) hang if Ethernet cable removed

embeddedemi-filteringethernetmicrochipusb

I need some help on debugging the issue faced on USB to Ethernet design. I have took reference form LAN9500Ai Development board.

Issue:- When Turn on the Power , USB to Ethernet work, and Three LED glow with one of them blinking. After that I removed the Ethernet cable and plug it back than it does not work. ( Sometimes All three LED light still glow even after removing the Ethernet Cable). My schematics is attached.

Schematics details:-
D6,D7,D8 and D9 NOT mounted.
R33 is Do not Mount
Connector J2 comes form PC USB port ( PC USB 5V convert to 3.3V via regulator than 3.3V apply to connector j2) , See attached
C2,C3,C4 and C5 Do not Mount.

Unsuccessful solution Tried
1. Mount C2,C3,C4 and C5 and No advantage
2. Remove R36 but no advantage

Successful solution Tried
1. Removed Connector J2 and reinsert then it Works, but again if i remove the Ethernet cord and reinsert it did not work. So every time after removing and reinserting cable i have to follow this

  1. In Schematics IC U3 pin , (manual Reset) , i tried to reset the LAN 9500 chip using this pin , and Chip get reset and it works, but again if i remove the Ethernet cord and reinsert it did not work. So every time after removing and reinserting cable i have to follow this

Please suggest how to resolve this problem, since in hardware i do not have reset control in current PCB version,

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(Schematics broke down to two above image, since do not know how to attached PDF file)

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Thanks

Best Answer

I had the same problem and it was simply a design error. I had mounted the LAN9500 but mounted the resistors according the LAN9500A, especially the 1MOhm of the oscillator was not mounted. Mounting the correct R solved the problem.

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