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I need some help figuring out why my ENC28J60 Chip is running hot. This is my first time using the chip and I'm not sure if I have everything right schematic-wise. I'm working on a prototype pcb I designed and ordered so I'm unable to use the breadboard approach of rewiring or swapping out components easily. I've followed (to the best of my knowledge) the example schematic in the datasheet as well as other resources online. The only difference that I'm aware of is that I used a 47uF capacitor on the VCAP pin instead of a 10uF cap. I'm not currently running any code on my MCU (ATXMEGA128A3U) other than flashing LEDs elsewhere on the board to test that the rest of the board is working. I'm too scared to keep running the chip that hot. I can hold my finger on it but its really warm. Does my schematic look correct and is there anything else I should check?

Schematic

http://i.stack.imgur.com/kRUYm.png

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The operating current of the ENC28J60 is typically 120mA inactive and 160mA active from a 3.3V supply. You can expect it to run warm as that's around half a watt. Depending on the case, the temperature could be around 65°C which would fit your description for a typical uncalibrated digit.

If you're ATXMEGA128A3U is running from 3.3V it should not cause any extra heating. If you've mixed supply voltages, that could cause problems.

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    \$\begingroup\$ I would also check the layout to see how much copper fill there is (any stitched vias to a nice fat ground plane) for heat dissipation per the layout recommendations for the part. \$\endgroup\$ – cowboydan Feb 13 '15 at 20:22
  • \$\begingroup\$ I've also noticed an ENC28J60 getting a little warm. Measure how much current your board is taking. \$\endgroup\$ – PkP Feb 13 '15 at 20:30
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The only difference that I'm aware of is that I used a 47uF capacitor on the VCAP pin instead of a 10uF cap.

Use the correct part here. VCAP is part of the 2.5V power regulation circuitry on the ENC28J60, and must be a 10 µF, low ESR capacitor. Using a different value, or the incorrect type of capacitor, is likely to cause problems.

It looks as though you've also "cheated" a little on the RBIAS resistor. This resistor must be 2.32 kΩ; the 2 kΩ resistor you've used is out of specification.

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