Author Topic: Current readings when MAC/PHY running?  (Read 5601 times)

Offline thamanjd

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Current readings when MAC/PHY running?
« on: August 21, 2007, 02:29:25 AM »
If anyone else is using this chip i'd be keen to find out what other peoples average current consumption is while running ethernet operations.

i get about 200mA. This seems a little high.
Anyone else?

John Dowdell

Offline mark

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Re: Current readings when MAC/PHY running?
« Reply #1 on: August 21, 2007, 11:53:03 AM »
Hi John

This value is consistent with my observations when the PHY is in 100M mode (200mA).
When operating in 10M mode the current consumption is more or less halved (100mA).

In fact I think that the 10M mode is quite efficient - I have observed that external PHYs often require more or less the same current consumption in both 10 and 100M modes. Eg. Davicom DM9161A states 92mA from 3V3 at 100M and 72mA at 10M.

There are devices which are better though - the well known CS8900A required 55mA from 5V (MAC + PHY), but this is only 10M with no processor. On the other hand there are also worse - the Microchip ENC28J60 (SPI) interfaced requires typically 120mA..180mA in 10M mode (doesn't support 100M) and again this is without any controlling processor.

It is a fact that the NE64 gets quite hot so good thermal dissipation is important in the PCB design.

I have also used the NE64 with an external PHY (EXTERNAL_PHY_USED can be passed as a parameter when initialising the Ethernet interface) and in this case the device stays cool, confirming that it is the PHY which requires the power when operating.

Regards

Mark

Offline thamanjd

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Re: Current readings when MAC/PHY running?
« Reply #2 on: August 23, 2007, 05:01:30 AM »
Thanks, excellent feedback. I guess that explains why the 80 pin version has the heatsink pad on the bottom.

John Dowdell