RG1 1.8v regulator

There's a report today of a guy who thinks there is a correlation

between hot chips and ethernet cutting out and keyboard repeats.

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=24&t=14478

"Mine gets pretty hot. Heat I don't mind, but when it does get hot,

the ethernet cuts out and the keyboard repeats happen more often."

I see that mahjongg has become an apologist now, and doesn't even realize when he's teaching Grandma to suck eggs.  Sad.  I guess the fanboi disease over there is contagious.

The Foundation has already found the reason for dropped USB events.  No further speculation is needed.

Thomas Johansen wrote:

 

Troy Mackay wrote:

 

Tooms wrote:

 

i will love to try out the hack Troy mackay has done also and then test again with that fix on the board, but i have looked into this and i most say it is very well done by Troy as i think it is to small for me todo and i done have an microscope as need for this.

 

so yes if some one can findout where to make an cut to split the LAN9512 1v8 from the lod 1v8 then i will try this also.

 

 

Tooms

The microsope is really handy (and didn't cost me a cent), you'd be surprised what you can do when you can see what it is you are doing. I haven't even done a lot of SMD work. I'd love one of those IR cameras though... They'd be a bit harder to find in someones junk bin.

 

Hi

 

yes i am only having an magnifying lamp the glass ones with 40 leds and it is not very good so i have been missing this for an long time..

 

I ask my local hacker space if they hade an good microscope but they only got an older fix one, have not seen it.. so i have now my own microscope on the way and hope it will be here in 7 days time and then i can try do the hack you have done..

 

I can see you only have split the VDD1V8CORE but what about the other VDD1V8ETH and VDD1V8USB ?

 

 

Tooms

Hi

hmmm replying on my own posts..

But i am getting (i hope ) an microscope to the coming weeking and then i will try to do the hack Troy mackay and then do some more testing to see if this fix the heat of the LAN9512 and to see how low the power the RPI can run from as i like to do an project where it is running from an battery so if i can save 30-40% in power use by do this hack and replace the LDO then it will be good.

Just hope they soon will make an fixed rev. of the board so i can buy more boards with out this error.

Tooms

I now find it amazing and enterteining to see that the minions resist to accept that there are problems with the R-pi. "Hey there is nothing wrong with the board, you already tested 12 keyboards, why not 13 ?" and why a kid should carry the R-pi on their backpack ? Some of us minions of the RPF carry it on our underware !!

Sigh ....

Meanwhile I see "no list" or any other info being "shared," and it surprises me that there is not a single bit of information on the main blog site.

As the issues become exponential it will start to backfire, I'd stop production and selling until the issues get fixed.

Meanwhile APC is making progress announcing Newegg.com as distributor for US and Canada.

-J

jamodio wrote:

 

Meanwhile I see "no list" or any other info being "shared," and it surprises me that there is not a single bit of information on the main blog site.

That's what the guy Sulge who got banned at the start of the "USB discussions getting a bit heated" thread said.

He got banned for only a week (perhaps a sign that some admins are starting to realized that the emperor has no clothes), so let's see what he says when he comes back and points out that the very problems he was describing were confirmed by the Foundation's engineers.

Meanwhile APC is making progress announcing Newegg.com as distributor for US and Canada.

Excellent, that makes it a lot more likely that a UK distributor will appear before long.  The APC and BeagleBone are the only two cheap boards with Ethernet MAC directly on the SoC instead of attached over USB, so I'm very favourably predisposed to it.

certainly there have been plenty of opportunities on the

RPi forum and twitter for someone to say yes we have a

design error and it is causing chip temperatures to get hotter

than they are supposed to.

On the recent "case with fan" thread:

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=63&t=14323

bredman replies:

"1. The chips in the RPi are supposed to run hot, they are designed to operate safely to 120 degrees C."

On twitter, a similar question about fans is asked:

https://twitter.com/scottfrye/status/234232917583343616

Liz's reponse is:

"we're making good progress on the heat issue that some of

you are experiencing, with expert help from the other forum."

Oh wait, that's not quite what she said.  Instead she said:

"Why do you need a fan?"

Ron K Jeffries further clarifies: "It runs very cool, even when

overclocked to 900MHz.  Unless you live in the Mojave desert,

you'll not need a fan."

I think you said it best some months ago, that facts and honesty "interfere with her right to a new kitchen".

coder27 wrote:

 

There's a report today of a guy who thinks there is a correlation

between hot chips and ethernet cutting out and keyboard repeats.

 

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=24&t=14478

 

"Mine gets pretty hot. Heat I don't mind, but when it does get hot,

the ethernet cuts out and the keyboard repeats happen more often."

Here's my latest hypothesis.  We're seeing three outcomes of the regulatory battle between RG1 (1.8V regulator) and IC3 (LAN9512).

1.  RG1 has substantially higher Vreg than IC3 and thus provides essentially all the current for 1V8.  IC3's regulator switches off and IC3 runs nice and cool.

2.  IC3 has substantially higher Vreg than RG1 and thus provides essentially all the current for 1V8.  IC3 get very hot, but still functions OK, at least for now.

3.  RG1 and IC3 have almost identical Vreg and the regulation is unstable, with the current alternately being sourced by RG1, IC3, or both, depending on RG1 and IC3 temperatures.

(3) is probably quite uncommon since it requires almost idential Vregs, but if it does occur might add enough ripple to 1V8 to cause USB and Ethernet failures.  It would be interesting to put a 'scope on 1V8 near IC3 to see what it looks like on boards with USB/Ethernet problems not otherwise explained.  It shouldn't affect IC3's PLL since the PLL has its own regulator and its own 1.8V filtering, but if IC3 is rapidly warming and cooling you might get some PLL instability.

It's also possible that (2) is causing local heating inside IC3 that's slowing a critical path enough to cause USB/Enet failure.  If path delay is right at the edge, process variation or case design could make the difference.

Good summary.  It's worth pointing out also that voltage is only one electrical parameter here.  If any instability is present, the added inductance from the incorrect connection could also be relevant given that the LAN9512 expects nothing but decoupling caps on these tracks.

The 1V8 LDO powers PLL circuitry in the LAN9512, so stability is important.  Those 3 caps won't be decoupling the LAN9512 as effectively if they're simultaneously part of a larger on-board 1.8V mesh, even if that mesh is not misbehaving electronically.

Morgaine Dinova wrote:

 

Good summary.  It's worth pointing out also that voltage is only one electrical parameter here.  If any instability is present, the added inductance from the incorrect connection could also be relevant given that the LAN9512 expects nothing but decoupling caps on these tracks.  The 1V8 LDO powers PLL circuitry in the LAN9512, so stability is important.

According to the LAN9512 data sheet (Figure 2.2 -- Power Connections), the PLL has its own +3.3V to +1.8V regulator.  It appears to be wired up correctly in the RasPi schematics.