high power consumption in ethernet mode

Post
Stri
Super Member
2008/03/27 23:01:07
Hello. After enabling the Ethernet module in my PIC18F87j60 I noticed, that it becomes really hot. I checked ICD2, and found, that current jumps from 90mA to 210mA, after ECON2bits.ETHEN = 1; So, is just this just a normal situation with the power, or there is something wrong? The module itself is working fine. Thanks.
post edited by Stri - 2008/07/03 01:21:28
SGeorge
New Member
RE: high power consumption in ethernet mode 2008/03/27 23:50:38
I have the same problem.
I builded my own board (PIC18f66j60), after the example of PICDEM.net2 board, using for voltage stabilizer LM317T (3.17 VDC stabilized on the board )with an output current rating up to 1.5 A.
When the ethernet module is on, conected to the router or not, its current on the centertap of the RJ45 connector (TS8P8C-PCB-TRAF) is 90 mA.The ethernet module is configured for ping response, for now, and working. The entire board current consummtion is 150 mA. The LM317T gets hot and the pic also, but not as much.

If I programm the board to light an led from the RJ45 connector, LEDA for example, the board current consumtion is 6 mA.

If somebody has any ideas for debugging please share.

George
O.Henry
Super Member
RE: high power consumption in ethernet mode 2008/03/28 01:34:08
The current figures from both of you are prefectly normal and expected.  All current-mode Ethernet PHYs use a whole lot of power.  Ethernet is designed for high speed, long distance, and high reliabilitiy (noise immunity).  All of these features generally require trade offs in power consumption.
SGeorge
New Member
RE: high power consumption in ethernet mode 2008/03/28 02:47:33
If I understand correctly, I can use the board without the fear of burning my pic?
 
Thanks for the help. 
SGeorge
New Member
RE: high power consumption in ethernet mode 2008/03/28 02:54:13
And what do you mean by "trade offs in power consumption"?
DarioG
Allm├Ąchtig.
RE: high power consumption in ethernet mode 2008/03/28 07:19:41
The PIC won't burn Smile rest assured.

The trade off is that, to get long distance and high speed communication, some more current is needed.
jamodio
Super Member
RE: high power consumption in ethernet mode 2008/03/28 11:56:23
 
Also if you check the "Electrical charateristics" section of the datahseet you will
see that max current can reach up to 300mA and power dissipation 1W.
 
The LM317 is an adjustable voltage regulator, not just 3.17V, also be aware
that you are very close to the lower limit (3.1V with the Ethernet module
enabled) of the recommended operating supply voltage.
 
My .02
 
Stri
Super Member
RE: high power consumption in ethernet mode 2008/03/30 23:30:46
I see. But it's kinda scary, anyway
SGeorge
New Member
RE: high power consumption in ethernet mode 2008/03/31 01:03:53
Thanks guys, i have modified the voltage on the board to 3.4Vdc, and I left it running for half of hour. It didn't burn wink.
Keep up the good work.
George
Stri
Super Member
RE: high power consumption in ethernet mode 2008/03/31 03:05:35
BTW, how to "trade off in power consumption"? If I just put some resistors between PIC and transformer to limit a current, it will help? I don't need in 100m lines or something...just 1 meter is enough...
post edited by Stri - 2008/03/31 03:53:59
DarioG
Allm├Ąchtig.
RE: high power consumption in ethernet mode 2008/03/31 04:17:54
Hmmm, no I don't think you can Smile