LAN chip becoming hot

[colin B]

I've noticed 3 posts on Element-14 Pi forum stating that their Pi's LAN9512 chip gets very hot, one person has added a heatsink to the chip and placed their board vertical in an airflow to solve this.

I have one from the first batch and don't have this problem, those reporting it seem to have had Pis from subsequent batches.

I was wondering if any one had any thoughts on this as I haven't seen anyone here report this or at Design Spark.

Colin

[johnbeetem]

This RasPi thread was started 14 May 2012: Ethernet chip gets raging hot,
http://www.raspberrypi.org/phpBB3/viewt ... =28&t=5898

[RaTTuS]

http://twitpic.com/a1sogy

but I've found in the past that LAN chips can get hot hot hot

slap a small Heatsink on if you are worried .

also see
http://hackaday.com/2012/06/23/checking ... pberry-pi/

[jbeale]

I think part of the confusion is the definition of "hot". In open air, my LAN9512 Eth/USB chip reaches about 52 C after some time. This is too hot to hold my finger on for more than about 5 seconds, but it is not unusually hot for an IC.

The data sheet for this chip
http://www.smsc.com/media/Downloads_Pub ... s/9512.pdf
in Table 4.1 on p.40 says it comes in two versions, rated for operation at an ambient temperature in still air TA = 70 C (commercial) or 85 C (industrial). It uses 763 mW at 3.3V with maximum traffic on 100baseT and both USB ports (Table 4.3.4, p. 42).