[En-Nut-Discussion] Ethernut 2.1 power consumption

Harald Kipp harald.kipp at egnite.de
Fri May 22 13:04:02 CEST 2009

Benoit Smeysters wrote:
> At present I use Ethernut1.3h board and I projet to buy Ethernut2.1.
> I want to compare the two board and I read http://www.ethernut.de/en/hardware.html
> As I cant see, Ethernut2.1 require a 400mA power supply instead 150mA for Ethernut1.3.
> I can read : "The penality for all these enhancements is an increased power consumption and heat dissipation, mainly caused by the fast Ethernet interface."
> For reduce this consumption, can I force the speed of the Ethernet controler at 10Mbps ?

So far Nut/OS doesn't support Ethernet rate switching due to the lack of

Actually the board draws less than 300mA, but still significanly more
than Ethernut 1. This is even the case when keeping the reset button
pressed. So I doubt that reducing the Ethernet speed would help much.

The LAN91C111 (industrial version) used on Ethernut 2 consumes much more
power than for example the 100Mbit DM9000E used on Ethernut 3 and the
EIR. However, if you look to the DM9000B, the industrial version, power
consumption is similar. Furthermore, I had been told by a customer, who
tested Ethernut 2 and 3 with one of these expensive analyzers, that the
Davicom chip did not reach the Ethernet requirements for signal
integrity, while the LAN91C111 shines.

Btw. we regularly test Ethernut 2 in a temperature chamber over the full
range and never experienced problems with the LAN controller. Some time
ago we have had problem with the LAN at temperatures below -20°C (-4°F),
but it turned out to be a problem with the 3.3V regulator:
The LAN controller itself never failed, although it easily reaches
temperatures of 70°C (158°F).


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