RG1 1.8v regulator

Wow.   That's worrying.

PS. It would be nice if you could include the images here directly, thumbnails at least.  Picasa is somewhat annoying because of its multiple required Javascript sources, and Google is developing quite a habit of turning off free services anyway ... as well as becoming evil. :-P

Thanks for starting to test this theory out.  I would really like to see the results of removing the RG1 off the Pi.  To bad i dont have a Pi laying around to do this do.

When my other Pis arrive I might be tempted to break out the soldering iron. In the mean time, I'm doing a bit of reading.

Looking at figure 2.2 of the 9512 datasheet (http://www.smsc.com/media/Downloads_Public/Data_Sheets/9512.pdf) would it be possible to cut the 3.3V input to the internal core regulator and have the core logic powered by an external (more efficient) 1.8V source? I'm not sure if this chip will run that way or how oversimplified this diagram is but it might be easier and more power efficient than trying to cut the link to the external 1.8V plane.

I'm guessing those VDD33IO pins do more than just feed into internal regulators though, or the chip would just run off 1.8V to start with.

I think it may be time to contact SMSC, and find out whether it's OK

to use the LAN9512 chip's 1.8V "output" pin to power other devices

in parallel with another LDO regulator.

The datasheet, p. 41, at:

   http://www.smsc.com/media/Downloads_Public/Data_Sheets/9512.pdf

shows power dissipation of 763mW.  But that probably doesn't account

for this scenario.  SMSC's tech support is available at:

https://www2.smsc.com/mkt/intforms.nsf/faemail

Wow.   That's worrying.

Well yeah.. but I think we've suspected what's going on since jamodio pointed out the error on the schematics.

PS. It would be nice if you could include the images here directly, thumbnails at least.  Picasa is somewhat annoying because of its multiple required Javascript sources, and Google is developing quite a habit of turning off free services anyway ... as well as becoming evil. :-P

My reason for using an external host for the pictures is fairly simple. Most forums I try to upload to seem to have ridiculous limits, like max size of 10k and a .JPG will upload but not a .jpg or .patch rendering the facility rather pointless. I also dislike the forums where you have to register and login to see the images, or where the column width is enforced and the image gets cropped. Finally I'm usually going to share these things with several different groups of people and a central point makes it easier.  I accept you may not agree with my reasons, but they are what they are.

So, if you can suggest someplace that meets the following: 1. not javascript encrusted, 2. not part of the evil empire, 3. free, 4. reasonably permanent,  I'd be more than happy to use it instead.

Just trying it here, not too bad with a 2MB size limit, but still scales down the image with the associated loss of detail.  So I'll at least try uploading stuff here too.

I'm guessing those VDD33IO pins do more than just feed into internal regulators though, or the chip would just run off 1.8V to start with.

Yeah, you'd have to assume they're used for 3.3v IO pins back towards the SoC at the very least. Not really clear if the internal regulator is from a single pin, or from many, or which one. So not clear if it's easier or not.

It's looking more like we need someone with a model A or who is prepared to pull the LAN9512 of the board to be able to measuer the RG1 current that way.  While I'm probably prepared to try that, I'm not there just yet

I think it may be time to contact SMSC, and find out whether it's OK

to use the LAN9512 chip's 1.8V "output" pin to power other devices

in parallel with another LDO regulator.

If it was acceptable to use it as an output I'd expect to see something in the DC specs to tell you how much current it can supply.  I'd also suspect that running it in parallel with another regulator isn't going to be a good idea regardless.

Just to expand on my original observations, the negative current I see on the output of RG1 seems to be due to it outputting 1.79v for a few seconds on initial powerup before stabilising at 1.804v. While the LAN9512 appears to power up at 1.805v and stay there.

selsinork wrote:

 

So, if you can suggest someplace that meets the following: 1. not javascript encrusted, 2. not part of the evil empire, 3. free, 4. reasonably permanent,  I'd be more than happy to use it instead.

 

Just trying it here, not too bad with a 2MB size limit, but still scales down the image with the associated loss of detail.

Thanks.

Aye, it's a problem indeed.  I think I'm going to use this "ARM revolution" to detach myself as much as possible from the various evil empires by hosting resources of various kinds myself on cheap and low-power ARMs, and removing them from the 3rd party sites.  It'll kill several birds with one stone.  It even makes sense in colos, because you can run a whole pile of ARMs within the typical least-cost rack power allocation.

Back to running my own servers like in the early days before we succumbed to the dark side.

Morgaine.

Selsinork,

>If it was acceptable to use it as an output I'd expect to see something in the DC specs to tell you how much current it can supply.  I'd also suspect that running it in parallel with another regulator isn't going to be a good idea regardless.

right.  But I think in order to actually get this fixed it's going to take more than suspicions that there's a problem. If SMSC can be prompted to issue a clarification, then Element14 might take notice, and if they do, then maybe RPF might take notice.  Otherwise it looks like they will go on indefinitely saying the chip may be running a little warmer than expected, but it's not hurting anything.