BBB startup current

[kzsolt...@gmail.com]

According our mesurment BBB has over 2A startup power peek just for 0,1ms.

This make it incompatible with some powersupply has advanced overquerrnet protection.

This power peek is normal?

There is any way to change startup current "policy" of board?

Thanks fo any advise.

[Gerald Coley]

All capacitors look like a short when they are discharged. What you are seeing is the capacitors on the board charging up. The board is not even powered up after .1ms.

Gerald

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[kzsolt...@gmail.com]

You are sure "all capacitor"?
I think TPS has no capability to flow trough more than 1A even in peek, therefore capacitor after TPC cannot generate 4A peak!?
Only capacitor charged directly in this phase is C2.

But only capacitor which can generate 4A peak is C34.
So TPS can flow trough more than 4A for a milisec?

I think there is missing som kind of FBB from P1 pin 1 beacuse the devlopment focused to USB power.

[Gerald Coley]

Sounds like you have it figured out.

Gerald

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[kzsolt...@gmail.com]

Before I forgot.

TPS not limit output capacitors, but recommend 22+10+10+10+10=62 uF. BBB use 100+10+10+10+10+10=140 uF. This is more than twice than recommended.

Furthermore TPS recommend not only capacitance but ESR of capacitors too (as 20mOhm). This is determine start-up current too.

BBB use C34 100uF as puffer to feed USB host connector. But it is not isolated from sys power line (need FBB?). Looks like this is where current peak originated from.  

TPS has soft start feature but only for DC-DC converters and LDOs. Therefore no soft start for capacitive load connected to SYS power line.

It is advisable to add some part to SYS power line for further models (e.g. Green).

But up to this moment I think it is recommended to use power supply with <=2.5A current limit to prevent damage of TPS. TPS has 3A absolute maximum current limit.  

[Gerald Coley]

OF all the board we have shipped, we have never lost a TPS5217C due to this issue. In fact, I think we have only lost maybe 5 TPS65217C devices total in 4+ years.

And as i said, you have to charge up those caps. I am not sure how to prevent caps from needing to be charged.

And as we also say, use a good power supply. That sometimes means not the cheapest ones.

The makers of the Green are certainly free to add whatever they like to their design.

. 

Gerald

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[kzsolt...@gmail.com]

"And as we also say, use a good power supply."

This was originator of the problem. At first time we try to use medical approved 4A PWS.But this type has a fast current protection circuit, which detect 1ms 4A current peek as short circuit.

So our advise is to use middle categhory PWS (we have success with MW GS15B-1P1J).

"we have never lost a TPS5217C due to this issue"

This is understandable beacuse average application is one BBB alone. This require 2A PWS which have no chance to harm TPS in this way.  

But in case of our special application more 5VDC powered device work together. This can be 2 or more BBB and more other device. This is why we try to use 4A or higher current PWS. This can demage TPS at startup.

"I am not sure how to prevent caps from needing to be charged"

You dont need it!

First what need to be learn by power rail diesigner is the rule: capacitive load on output of power regulator is very sensitive area. This is why power regulator manufacturer (including TI) using pages to explain its calculation.

Loading reagulator with high/low/good/bad capcitor have diffrent effect to stabilized power rail.

At first impression 100uF at position C34 is very high for regulator output (ext PWS). The 22uF with ESR=20mOhm (TI rec.) limit startup peak to normal value.

Moreover I cant known philosophy of USB host interface designer, why need 100uF at IN of PDS? All AN of TPS20x1 PDS are recomend 0,1 to 10uF at this position except "Typical Hot-Plug Implemantation" where 1000uF applied. But this is not match, beacuse you cannot Hot-Plug USB host interface to BBB beacuse it is hardwired.

I think it is some missplacing of this capacitor. USB 1.1 require ~100uF at downsteram port. But this capcitor must be connceted at output of TPS20x1 not at input of. This provide a soft charge for system power rail. At input need just <=10uF.

[Gerald Coley]

The USB specification requires 100uF on the USB ports. TI did not write that specification. Trust me. I know.

If you put the CAP after the switch then it tends to pull down the 5V input when you activate the USB power, something about charging that cap. It works better before the switch as it prevents a dip on the 5V rail, which caused issues with the PMIC, power rail going low after power up.

I am not going to make any changes to the design. Fell free to convince the Green people to change their design.

As to your specific application, I did not design the board for your application. I did however give it to you for free. Feel free to make whatever changes you need for your application and build you own board. I think the statment on the first page of the schematic is self explanatory.

Gerald

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[kzsolt...@gmail.com]

First of all making changes on design "tomorrow" is irresponsible, so I never request it. But good to know where is some "leak" in design. For example it is help to make workaround.

"TI did not write that specification"

No, but use it in all reference design. See TI TPS20x1 PDS application information. See for example TPS2051 docu Fig 33.

"If you put the CAP after the switch then ..."  

Then why CAP placed OUT of PDS in all TI application information? 

Because PDS has soft start feature which prevent overload IN (BBB SYS power rail). See for example TPS2051 docu Fig 4 and 8.

Fig 8 is perfect draw for this. The soft start feature limit charge of 100uF to 0,5A, therefore current never exceed USB1 and 2 current limit, therefore no dip on IN.

This is one main function of PDS.

"I did not design the board for your application"

It is not required. But during research work to specify our problem I found many topic where users discover mysterious problems with power supply, and try to found a right one for BBB. This can be originated from startup current peak.

[Gerald Coley]

Thank you for your feedback. 

Gerald

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[William Hermans]

kzsoltkzsolt,

I would like to point out to you that you're talking to *the* person who designed the beaglebones, who also used to work for Texas Instruments at some point in his career. Someone who has made his designs free of charge to the public, which he has made perfectly clear to you in these post that you're free to change and use for your own personal use.

So, telling him things, he probably already knows, in hopes of making yourself looks good. Actually make you look like a "know it all". e.g. it doesn't make you look good.

SO perhaps you should realize that Gerald is probably well aware of what you're trying to discuss here, but is unwilling to change for various reasons. Reason, that you, I, or the next person do not need to understand. Because we can change to designs to our own liking if we so wish.

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[John Syne]

Pay no attention to William. You comments are welcome and Gerald has accepted your comments as valuable input by thanking your for your feedback. Now, let me address your concerns:

1) The power supply used to power the BBB should be selected so that it does not damage the BBB, so a 2A power supply was specified. If you wish to change that specification, then the onus is on you to verify that a 4A power supply will not damage the BBB. Your conclusion that is may damage the BBB means that you should not use a 4A power supply. In addition, a power supply that is spec’d at 4A should not shutdown when it sees a 4A load, but rather, it should current limit at 4A. If the power supply is spec’d at 4A, then 4A should not be treated as a short circuit. 

2) The TI spec for the TPS65217C is a general recommendation as they are unaware of how you are going to use the part. The BBB SYS_5V powers several subsystems, including HDMI, I/O (VDD_3V3B) and USB. Clearly you could move the 100uF to the other side of the TPS2051, but then you need an additional capacitor on the SYS_5V which increases the cost and doesn’t provide any clear benefit, if you choose the correct power supply.

3) As Gerald has pointed out, the BBB is just a reference design. It was designed as a low cost solution which meant that tradeoffs were required to keep the price low. Clearly things could have been done differently, but then the BBB price would have been much higher and the board larger. Given that most users would probably not need these extra features, they were not incorporated into the current design. There are several spinoffs of the BBB, some with wifi, some with more RAM, etc, but none have been as successful as the BBB. 

4) While I have provided Gerald input into both the BBB and BeagleBoard-x15 designs, I ultimately defer to his judgement because he has the track record or having designed several products that are very successful. 

From my prospective, the BBB design is good, but your input was none the less valuable. 

Regards,

John

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[Harvey White]

On Mon, 4 Jul 2016 15:13:00 -0700, you wrote:

>Pay no attention to William. You comments are welcome and Gerald has accepted your comments as valuable input by thanking your for your feedback. Now, let me address your concerns:

From my own engineering standpoint (and opinions will, of course,
vary):

>
>1) The power supply used to power the BBB should be selected so that it does not damage the BBB, so a 2A power supply was specified. If you wish to change that specification, then the onus is on you to verify that a 4A power supply will not damage the BBB. Your conclusion that is may damage the BBB means that you should not use a 4A power supply. In addition, a power supply that is spec’d at 4A should not shutdown when it sees a 4A load, but rather, it should current limit at 4A. If the power supply is spec’d at 4A, then 4A should not be treated as a short circuit.

I would have designed the power supply circuitry so that with a power
supply of appropriate minimum rating, the maximum rating would not
have mattered. Using a power supply with a maximum current rating to
avoid damaging circuitry is not (again, IMHO) the best solution. If,
because of economic considerations, that decision is made, then it is
imperative of the designer to put this information specifically in the
power supply recommendations. Not doing this leads to damage, doing
this puts the responsibility on the user. Is this a "before the
design/after the design"? I don't know, and I don't remember (either
way) if this warning was ever in the power supply requirements.
Hindsight is 20/20, of course. If it's that important, then perhaps
the documentation needs to be changed. Decision not up to me.

>2) The TI spec for the TPS65217C is a general recommendation as they are unaware of how you are going to use the part. The BBB SYS_5V powers several subsystems, including HDMI, I/O (VDD_3V3B) and USB. Clearly you could move the 100uF to the other side of the TPS2051, but then you need an additional capacitor on the SYS_5V which increases the cost and doesn’t provide any clear benefit, if you choose the correct power supply.

"correct power supply" bothers me. I'm familiar with minimum current
capacity, voltage limits, short circuit current limits (infrequently
applied). Again, "a 4 amp power supply will allow the board to damage
itself, so we depend on a 2 amp maximum supply to avoid damage." This
could be discussed a bit....

>3) As Gerald has pointed out, the BBB is just a reference design. It was designed as a low cost solution which meant that tradeoffs were required to keep the price low. Clearly things could have been done differently, but then the BBB price would have been much higher and the board larger. Given that most users would probably not need these extra features, they were not incorporated into the current design. There are several spinoffs of the BBB, some with wifi, some with more RAM, etc, but none have been as successful as the BBB.

Hmmm, well, perhaps (although not required) it might be nice to know
what the engineering limitations are of the design.

I've seen 1) the ones I know about, and 2) the ones I haven't found
out yet... and 3) the ones people are going to have to tell me
about...

and I do like paranoid designs.....

Harvey

>4) While I have provided Gerald input into both the BBB and BeagleBoard-x15 designs, I ultimately defer to his judgement because he has the track record or having designed several products that are very successful.
>
>From my prospective, the BBB design is good, but your input was none the less valuable.
>
>Regards,
>John
>
>
>
>
>> On Jul 4, 2016, at 2:11 PM, William Hermans <yyr...@gmail.com> wrote:
>>
>> kzsoltkzsolt,
>>
>> I would like to point out to you that you're talking to *the* person who designed the beaglebones, who also used to work for Texas Instruments at some point in his career. Someone who has made his designs free of charge to the public, which he has made perfectly clear to you in these post that you're free to change and use for your own personal use.
>>
>> So, telling him things, he probably already knows, in hopes of making yourself looks good. Actually make you look like a "know it all". e.g. it doesn't make you look good.
>>
>> SO perhaps you should realize that Gerald is probably well aware of what you're trying to discuss here, but is unwilling to change for various reasons. Reason, that you, I, or the next person do not need to understand. Because we can change to designs to our own liking if we so wish.
>>

>> On Mon, Jul 4, 2016 at 1:55 PM, Gerald Coley <ger...@beagleboard.org <mailto:ger...@beagleboard.org>> wrote:
>> Thank you for your feedback.
>>
>> Gerald
>>

>> On Mon, Jul 4, 2016 at 3:18 PM, <kzsolt...@gmail.com <mailto:kzsolt...@gmail.com>> wrote:
>> First of all making changes on design "tomorrow" is irresponsible, so I never request it. But good to know where is some "leak" in design. For example it is help to make workaround.
>>
>> "TI did not write that specification"
>> No, but use it in all reference design. See TI TPS20x1 PDS application information. See for example TPS2051 docu Fig 33.
>>
>> "If you put the CAP after the switch then ..."
>> Then why CAP placed OUT of PDS in all TI application information?
>> Because PDS has soft start feature which prevent overload IN (BBB SYS power rail). See for example TPS2051 docu Fig 4 and 8.
>> Fig 8 is perfect draw for this. The soft start feature limit charge of 100uF to 0,5A, therefore current never exceed USB1 and 2 current limit, therefore no dip on IN.
>> This is one main function of PDS.
>>
>> "I did not design the board for your application"
>> It is not required. But during research work to specify our problem I found many topic where users discover mysterious problems with power supply, and try to found a right one for BBB. This can be originated from startup current peak.
>>
>>
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>>
>> --
>> Gerald
>>
>> ger...@beagleboard.org <mailto:ger...@beagleboard.org>
>> http://beagleboard.org/ <http://beagleboard.org/>
>> gco...@emprodesign.com <mailto:gco...@emprodesign.com>
>>
>>
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[John Syne]

Harvey, you raised several very good points. I cannot say I disagree with anything you said.

Regards,
John

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[Harvey White]

On Mon, 4 Jul 2016 15:46:43 -0700, you wrote:

>Harvey, you raised several very good points. I cannot say I disagree with anything you said.

Thank you. I prefer paranoid designs myself. However, I don't design
commercial products, I design stuff for myself. It does make a
difference. If I get it wrong, I have to fix it... and I have LOTS
of stuff to fix myself.

I also don't have to design to a price point, at least, not as much as
for a commercial product.

Harvey

[Gerald Coley]

When you design low cost hardware, you have to make certain decisions to get the cost down.

1) As few components as possible.

2) Limit the application. Only one application, 

3) Push as much cost outside, for example the power supply.

4) Lowest cost components.

5) Limit the features.

6) Cut the profit.

Yes, there are several things I could have done different. Many of these no one has even identified. But if I had, you would not have bought it because it cost too much. After all hardware is supposed to be cheap. That is where the value is, in the price. Not the value..

Nobody asked how I took it from $89 to $49. They just bought them up and complained that it didn't do all the things they wanted it to do for $49.

If anyone of you want to change the design, add more features, make it more robust, add more cost, increase the price, manufacture it and sell it, by all means, go ahead. I am sure there will b a few folks that value the hardware and recognize that value, and will pay for it.  

But, I suspect the majority will complain that it is too expensive and will stay with the BBB and instead ask how to flash the latest image in the BBB and why does my my GPIO does not work..

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[William Hermans]

When you design low cost hardware, you have to make certain decisions to get the cost down.

1) As few components as possible.
2) Limit the application. Only one application,
3) Push as much cost outside, for example the power supply.
4) Lowest cost components.
5) Limit the features.
6) Cut the profit.

Yes, there are several things I could have done different. Many of these no one has even identified. But if I had, you would not have bought it because it cost too much. After all hardware is supposed to be cheap. That is where the value is, in the price. Not the value..

Nobody asked how I took it from $89 to $49. They just bought them up and complained that it didn't do all the things they wanted it to do for $49.

If anyone of you want to change the design, add more features, make it more robust, add more cost, increase the price, manufacture it and sell it, by all means, go ahead. I am sure there will b a few folks that value the hardware and recognize that value, and will pay for it.  

But, I suspect the majority will complain that it is too expensive and will stay with the BBB and instead ask how to flash the latest image in the BBB and why does my my GPIO does not work..

Exactly, or close enough to what I was getting at. So Instead of me saying: "Pay no attention to John, as he tends to pontificate on others comments, and has no idea what the hell he is talking about." Let me just say that I figured Gerald had the sole purpose of designing this board to work "good enough" while remaining within a specified price range. e.g. it works, and it's cheap.

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[William Hermans]

@Gerald

Actually, my buddy and I would have bought the white, if that's all that was available. So, much to our surprise when the beaglebone black was announced . . . we immediately jumped on the pre-order list for two boards . . .

Would we have prefered you did one thing, or another slightly differently ?  Sure ! But as it is, you saved us 50% right away, by doing what you did with the BBB versus the BBW. So . . . we nite our lip. Then implement what we have to on the side to make the BBB work for our own application. Too bad many youngsters would prefer to complain about what the board *ISNT* versus what the board *IS*.

[William Hermans]

So, we bit our lip *

[Gerald Coley]

Thanks for the words. But, I think my days are numbered here. 

Gerald

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[William Hermans]

Thanks for the words. But, I think my days are numbered here.

Gerald

That's a shame. Truly. You've contributed much in the last several years since the original beagleboard. I can imagine without project like this that many other boards like the nVidia Jetson K1 would not be available.

But . . . I think I understand where you're coming form. Aside from the thanklessness.

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[Harvey White]

On Mon, 4 Jul 2016 18:02:13 -0500, you wrote:

>When you design low cost hardware, you have to make certain decisions to
>get the cost down.
>
>1) As few components as possible.

granted, no problem with that.

>2) Limit the application. Only one application,

do we know what the application is? Apparently people tend to think
that this can do anything.

>3) Push as much cost outside, for example the power supply.

hmmm, then that says you have not as much control over the power
supply as you might want. Certainly not as much as you may like.

>4) Lowest cost components.
no problem.
>5) Limit the features.
no problem. It does what it does.

>6) Cut the profit.
diminishing returns.

>
>Yes, there are several things I could have done different. Many of these no
>one has even identified.

Perhaps it might be interesting to know what they were... Not
criticizing, but to know design alternatives might be nice.

>But if I had, you would not have bought it because
>it cost too much. After all hardware is supposed to be cheap.

I'd personally disagree. Hardware costs as much as you pay for, and
does what you design it to do. I, for one, am willing to pay more for
more capability, within reason. Not your typical consumer,
though.....

>That is where
>the value is, in the price. Not the value..

Then you're designing to a price point, and that's a different thing
entirely.

>
>Nobody asked how I took it from $89 to $49. They just bought them up and
>complained that it didn't do all the things they wanted it to do for $49.

I'm not even aware that your initial design was 89 dollars. I might
not have bought it for that, but that would have been my decision. "I"
however, am not "they".... but there are a lot more of "them" than
there are of me....

Not practical for you to put too many blank pads on a board and expect
the user to solder parts in. I do, because I can build the boards.
Your average hobby type... not likely I suspect.

>
>If anyone of you want to change the design, add more features, make it more
>robust, add more cost, increase the price, manufacture it and sell it, by
>all means, go ahead. I am sure there will b a few folks that value the
>hardware and recognize that value, and will pay for it.

If I needed something with that capability, I'd probably buy it
because my cost preference on a PC board is 2 layers and not 4 or 6. I
don't have the money to develop a product at this level, nor do I have
the desire, nor perhaps the time or expertise.

The cost would, of course, determine how many I'd use, and for what,
but that's a simple economic decision. Then there's the engineering
decision.

>
>But, I suspect the majority will complain that it is too expensive and will
>stay with the BBB and instead ask how to flash the latest image in the BBB
>and why does my my GPIO does not work..

Can't help you with that....


Harvey

>> > For more options, visit https://groups.google.com/d/optout.
>>
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>> .

[John Syne]

@William

The part I was referring to is your constant need to second guess peoples motives and intentions. This is an open forum and developers are always welcome to provide their input. I don’t know why you constantly have this compelling need to denigrate people on this forum. Gerald doesn’t need you to protect him. He is more than capable of defending himself and his product. I acknowledge your contributions to helping people on this forum, but  it pisses me off when I see you tear into people for no apparent reason. Stay away from the personal stuff. 

Regards,

John

[William Hermans]

HI Harvey,

I'd personally disagree.  Hardware costs as much as you pay for, and
does what you design it to do.  I, for one, am willing to pay more for
more capability, within reason.  Not your typical consumer,
though.....

Id disagree with you. Only because we can second guess each other until the end of time. But the point here that this was part of the reasoning for the design behind the BBB, and without it we would not be where we are.

I'm not even aware that your initial design was 89 dollars.  I might
not have bought it for that, but that would have been my decision. "I"
however, am not "they".... but there are a lot more of "them" than
there are of me....

The initial design discussed here is the BBW I believe. By the time my biddy and I priced the BBW actually, the cost was $99.

If I needed something with that capability, I'd probably buy it
because my cost preference on a PC board is 2 layers and not 4 or 6. I
don't have the money to develop a product at this level, nor do I have
the desire, nor perhaps the time or expertise.

The cost would, of course, determine how many I'd use, and for what,
but that's a simple economic decision.  Then there's the engineering
decision.

Problem is, if this design was only a 2 layer design. the actual board dimensions probably would have increased 5x or more.

>But, I suspect the majority will complain that it is too expensive and will
>stay with the BBB and instead ask how to flash the latest image in the BBB
>and why does my my GPIO does not work..

Can't help you with that...

If you want my take on this situation . . . it's because the I.Q. of the average person posting on theses forums seems to have diminished in the last couple of years. These people can not understand that the software people on this project are not paid and offer their service for free to the community. As well as software upgrades are not the responsibility of the community, nor are these upgrade required for the software that third parties have written to work properly. Nor, do these third parties take responsibility for doing so . . . I could go on all day . . .

To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/rarlnbptmkkr2fs2hjqudj543mckujfv0r%404ax.com.

[William Hermans]

And, of course, I'm sure John has something to say, about what I have to say. Good thing for me, and everyone else who reads these posts. that I have blocked his posts on this forum. Globally.

[John Syne]

You cannot get the board layout done with 2 layers and you would have all kind of issues with power supply noise, ground bounce, etc. You have to start with 2 power planes and then you need at least 4 layers to get the signals out from the processor. You will not be able to route the board on 2 layers. You need a minimum of 4 routing layers and add 2 power planes and so you have a minimum of 6 layers.

Regards,
John

[Harvey White]

On Mon, 4 Jul 2016 16:41:47 -0700, you wrote:

>HI Harvey,
>
>I'd personally disagree. Hardware costs as much as you pay for, and
>does what you design it to do. I, for one, am willing to pay more for
>more capability, within reason. Not your typical consumer,
>though.....
>
>Id disagree with you. Only because we can second guess each other until the
>end of time. But the point here that this was part of the reasoning for the
>design behind the BBB, and without it we would not be where we are.

It's not second guessing. We're (to me) looking at different design
goals. I'm willing to pay more to have a feature if I want it. Price
point is simply that, 5 more dollars and who knows how many customers
you lose?

Because I design *my* stuff (to my own price points....) it's a matter
of divergent design goals. Not right or wrong, just different.

>
>I'm not even aware that your initial design was 89 dollars. I might
>not have bought it for that, but that would have been my decision. "I"
>however, am not "they".... but there are a lot more of "them" than
>there are of me....
>
>
>The initial design discussed here is the BBW I believe. By the time my
>biddy and I priced the BBW actually, the cost was $99.

Ah, now that is a different product. Different design goals.

>
>
>If I needed something with that capability, I'd probably buy it
>> because my cost preference on a PC board is 2 layers and not 4 or 6. I
>> don't have the money to develop a product at this level, nor do I have
>> the desire, nor perhaps the time or expertise.
>>
>> The cost would, of course, determine how many I'd use, and for what,
>> but that's a simple economic decision. Then there's the engineering
>> decision.
>>
>
>Problem is, if this design was only a 2 layer design. the actual board
>dimensions probably would have increased 5x or more.

From my experience, perhaps a factor of 2 IF the board could be routed
properly. With added layers, there's a factor that makes the board
more stable, gives better performance (due to transmission line
effects and signal isolation), and is often easier to route in a
particular size. The physical cost is that the board can cost twice
as much (at least).

>
>>But, I suspect the majority will complain that it is too expensive and will
>>stay with the BBB and instead ask how to flash the latest image in the BBB
>>and why does my my GPIO does not work..
>
>Can't help you with that...
>
>
>If you want my take on this situation . . . it's because the I.Q. of the
>average person posting on theses forums seems to have diminished in the
>last couple of years. These people can not understand that the software
>people on this project are not paid and offer their service for free to the
>community. As well as software upgrades are not the responsibility of the
>community, nor are these upgrade required for the software that third
>parties have written to work properly. Nor, do these third parties take
>responsibility for doing so . . . I could go on all day . . .

I think that the BBB has transitioned from a somewhat specialized
product supported by hobbyists to a commodity. Commodities are bought
by appliance users (a term borrowed from the amateur radio community).
The mindset is quite different. The expectations of the consumer are
also quite different.

If you think the BBB is bad, I think we should both consider the
Arduino world....

[Harvey White]

On Mon, 4 Jul 2016 16:49:05 -0700, you wrote:

>You cannot get the board layout done with 2 layers and you would have all kind of issues with power supply noise, ground bounce, etc. You have to start with 2 power planes and then you need at least 4 layers to get the signals out from the processor. You will not be able to route the board on 2 layers. You need a minimum of 4 routing layers and add 2 power planes and so you have a minimum of 6 layers.

I wasn't considering a modification of an ARM design, I was thinking
more of different processors. My preference (and cost limitations) as
well as what I already have software for, point me to other
processors. If I were to use ARM processors ( a possibility), I'd be
working with a pre-made board of some sort, due to manufacturing
difficulties.

Harvey

[William Hermans]

It's not second guessing.  We're (to me) looking at different design
goals.  I'm willing to pay more to have a feature if I want it.  Price
point is simply that, 5 more dollars and who knows how many customers
you lose?

Because I design *my* stuff (to my own price points....) it's a matter
of divergent design goals.  Not right or wrong, just different.

Ah, ok, I get that.

Ah, now that is a different product.  Different design goals

Absolutely. The BBW for us would have worked fine, but many of the cool features like onboard JTAG simply was not needed for our design goals, but seemed to have added a lot of costs that we would have preferred not to pay. So for us, in this context, Gerald was bang on with his designed goals. But was it perfect ? Probably not, but how many here would profess to "looking a gift horse in the eye" ? Also, many of use could look at these so called design flaws as an opportunity. I'm already making money from one such "flaw",  that is actually not a flaw. But a design / cost decision.

From my experience, perhaps a factor of 2 IF the board could be routed
properly.  With added layers, there's a factor that makes the board
more stable, gives better performance (due to transmission line
effects and signal isolation), and is often easier to route in a
particular size.  The physical cost is that the board can cost twice
as much (at least).

Well my own comments here were rather . . . yeah I do not know what. I'm not an EE, with experience in design layout. But I do have some understanding of the process, as one of my long time friends is very good with orcad, and design layout. So, I'm sure there is more than dimensions to consider in this design. For instance, I know that the DDR traces have to be very exact. A two layer design would surely have an impact on that, if not more . . .

I think that the BBB has transitioned from a somewhat specialized
product supported by hobbyists to a commodity.  Commodities are bought
by appliance users (a term borrowed from the amateur radio community).
The mindset is quite different.  The expectations of the consumer are
also quite different.

If you think the BBB is bad, I think we should both consider the
Arduino world....

I do not know much about the Arduino world. I prefer not to think about Arduino's period. My buddy here who is a very good EE, and has been an EE for 35+ years tells me he thinks the Arduino is awesome. Because it puts hardware in the hands of novices, and give them the ability to "make". My take on this is quite the opposite actually . . .

But here is the thing, 3.5+ year ago I entered into the world of Beagle knowing nothing. So I can understand the frustration of not knowing how to deal with a given situation. I have even once or twice "bitten someones head off" because I was frustrated. The thing is, my inability to understand something is not someone elses problem, or responsibility.  Which I realized even as I complained silently to myself . . .so I forced myself to learn, instead of blaming someone else for my inabilities. Now, I understand more about this hardware, and perhaps a good bit more about embedded Linux. But *ONLY* because I put effort into it. Well, others have helped some too, but no one did anything for me. Others helped as I helped myself to learn enough to ask a smart question.

Honestly I think I can count the "real" questions I've asked on these groups on one hand. I've asked Robert many questions in relation to other posts he replied to from others. But questions I started myself . . . very few. So why is this important ? It's important because 99% of the time it's best to go out and find the answer for yourself, and make sure you get the correct answer. Versus getting the wrong answer right away from someone else. There are of course exceptions, such as asking Robert specific questions about things in his domain. Not only that, but going out and finding your own answers sets you up as a problem solver. Someone who can think their own way out of things, versus being a hindrance on the community.

Anyway, this all ties to people making false assumptions on these groups and getting huffy / puffy, and claiming that x.y.z platform is better because of a.b.c. But guess what ? Beagle hardware has no direct comparison out there. So if peopel in this situation do as they claim, they're only hurting themselves. Most of these people though , , I tend to view as dim witted want-to-be's. People who want to run a media player app/ shell / whatever, and nothing else WHICH, in this persons humble opinion is not where this hardware shines . . .anyway, I'm starting to rant. Perhaps I should call it quites for now.

To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/64ulnb1nt32osthndtd0o39cg5bh6vdvfv%404ax.com.

[William Hermans]

By the way, Happy 4th to all you 'Merican's' of which I am one too ;)

[Morgaine]

John Syne writes:

> a power supply that is spec’d at 4A should not shutdown when it sees a 4A load, but rather, it should current limit at 4A. If the power supply is spec’d at 4A, then 4A should not be treated as a short circuit.

That's impossible.  You can't recommend that fundamental electrical laws be overridden. :P

If a PSU current limits at 4A, it can do so only by reducing its output voltage.  This may then drop below specification for its load and this can have very bad consequences such as non-stop rebooting.  There is no way for the voltage to be maintained above its minimum spec while still providing a current limit.

This is the reason why ensuring that startup inrush transients cause no harm must always be handled within the design of the load, ie. the BBB in this case.  The load is a black box as far as the external PSU is concerned, so the external PSU has no means to perform this protective function while still maintaining regulation.  (Blowing a fuse does not maintain regulation, but is sometimes the only practical alternative.)

In other words, a load can demand a minimum current capability under a rated voltage specification, but it cannot demand a maximum current capability unless it can cope with arbitrary drops in supply voltage.  Such voltage tolerance is generally not available in electronic circuitry today, certainly not in BBB.

[John Syne]

Nonsense. This is how the vast majority of power supplies work. The voltage ramps up while the current is maintained at it’s maximum current. When the voltage reaches the regulation voltage, the current is reduced. What the OP proposed is that 4A was regarded as a short circuit and hence the power supply shutdown. This is not normal. 

Regards,

John

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[Mark Lazarewicz]

:-) I've often wondered how many people post in here trying to be seen as knowledgeable.  Great comments William 

Sent from Yahoo Mail on Android

To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CALHSORo-TL2x_vUEni%2B-daiSEQXxLUU_N5p%2BEh%2Bt6tzpuuPT0g%40mail.gmail.com.

[Harvey White]

On Mon, 4 Jul 2016 20:27:22 -0700, you wrote:

>Nonsense. This is how the vast majority of power supplies work. The voltage ramps up while the current is maintained at it’s maximum current. When the voltage reaches the regulation voltage, the current is reduced. What the OP proposed is that 4A was regarded as a short circuit and hence the power supply shutdown. This is not normal.

Much of this depends on the type of supply.

A bulk supply provides unregulated current to the limit of its
capacity. Voltage decreases as current is drawn. There are no
voltage or current regulating elements. Obviously not used for the
BBB.

A voltage regulated supply may or may not have a current limit
circuit.

If not, then the supply current is limited by the resistance of the
parts. From zero, the supply will try to charge up whatever
capacitance is on the output. Large startup currents can happen,
similar to a bulk supply. The voltage regulator does keep the output
voltage from rising past a set point, however.

A voltage and current regulated supply may operate in two ways
depending on the current limiter design.

If the supply is only current limited, then the supply is a constant
current supply at startup, supplying the maximum current it can
(depending on load) until the nominal voltage is reached (assuming
we're charging capacitors). Under normal operation, the supply is a
voltage regulated supply. Should current demand exceed (or try to)
the current limit, the supply becomes a constant current supply. The
voltage drops to the point where the rated maximum current flows.

For instance, 5 volts 4 amps. Put a 2 ohm load on the supply and you
have 5 volts at 2.5 amps load. Put a 1 ohm load on it, and you will
have a 4 volt supply at 4 amps.

It is possible for a supply to have foldback current limiting. In
that case, the maximum supply current changes on maximum draw. In
this case, you may have a 200 ma current foldback limit. Try to draw
4 amps and the supply changes its limit to 200 ma and adjusts the
output voltage to maintain that lower limit. Depending on the design
of the foldback, the load may have to be reduced or disconnected to
restore the regulated voltage.

Constant voltage with constant current limiting is common on lab
supplies, higher quality wall-wart power supplies, and is not common
on straight battery supplies, or bulk supplies, and some older (and
cheaper) power adaptors.

Power limiting can be built in rather easily, though, if you have the
right parts.

Harvey

>
>Regards,
>John
>
>
>
>
>> On Jul 4, 2016, at 6:14 PM, 'Morgaine' via BeagleBoard <beagl...@googlegroups.com> wrote:
>>
>> John Syne writes:
>> > a power supply that is spec’d at 4A should not shutdown when it sees a 4A load, but rather, it should current limit at 4A. If the power supply is spec’d at 4A, then 4A should not be treated as a short circuit.
>>
>> That's impossible. You can't recommend that fundamental electrical laws be overridden. :P
>>
>> If a PSU current limits at 4A, it can do so only by reducing its output voltage. This may then drop below specification for its load and this can have very bad consequences such as non-stop rebooting. There is no way for the voltage to be maintained above its minimum spec while still providing a current limit.
>>
>> This is the reason why ensuring that startup inrush transients cause no harm must always be handled within the design of the load, ie. the BBB in this case. The load is a black box as far as the external PSU is concerned, so the external PSU has no means to perform this protective function while still maintaining regulation. (Blowing a fuse does not maintain regulation, but is sometimes the only practical alternative.)
>>
>> In other words, a load can demand a minimum current capability under a rated voltage specification, but it cannot demand a maximum current capability unless it can cope with arbitrary drops in supply voltage. Such voltage tolerance is generally not available in electronic circuitry today, certainly not in BBB.
>>
>>
>>
>> --

>> For more options, visit http://beagleboard.org/discuss <http://beagleboard.org/discuss>

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>> For more options, visit https://groups.google.com/d/optout <https://groups.google.com/d/optout>.

[Morgaine]

John Syne writes:

> Nonsense. This is how the vast majority of power supplies work. The voltage ramps up while the current is maintained at it’s maximum current. When the voltage reaches the regulation voltage, the current is reduced.

How?  By magic? :P

You appear to think that current limiting "just happens", without understanding how it's actually done.  It cannot be done without affecting the supplied voltage, as that is core electrical theory.

It doesn't matter how a PSU implements current limiting internally.  It could be manipulating effective internal resistance with linear devices, or it could be altering buck/boost frequencies or duty cycles, or it could be controlling linear or packetized charge injection into a capacitive tank, or in a fun Heath Robinson world it could even be using stepper motors to switch between transformer or inductor windings, but it really doesn't matter how.  Regardless of the internal technique in use, the end result is that when the current limit is reached and fractionally exceeded, the PSU will always and under all circumstances reduce the voltage supplied to the load that is demanding the excess current.  There is no alternative available in circuit theory.

And if the load keeps on demanding more current, that supply voltage will keep on dropping, until it goes out of spec and then "bad things happen".

You won't understand this until you check it out yourself --- easily done, just grab a programmable PSU, set a current limit on it, watch the voltage on a separate DVM, and reduce your load resistance to demand more current.  Good luck trying to keep the voltage fixed when you hit the current limit.  Not gonna happen. :-)

Incidentally, it's very important that you try this and understand it.  Nothing in electronics will make any sense to you until this is fully comprehended, as it's such a fundamental part of circuit theory.

[William Hermans]

:-) I've often wondered how many people post in here trying to be seen as knowledgeable.  Great comments William

Perhaps a poor choice of words . . .but both definitely know more about power electronics than I. Which I'm afraid isn't saying much.

To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/1046652277.1700874.1467693539920.JavaMail.yahoo%40mail.yahoo.com.

[John Syne]

Clearly you are not listening. I already said the voltage will drop and then rise as the capacitor charges, but the current will be constant until the voltage reaches the regulator voltage. All these references to all kinds of power supplies is senseless. We are only talking about the 5V2A supply recommended for the BBB, or the 5V4A supply suggested by the OP. If the power supply is spec’d at 2A, you are not going to get 10A because the power supply will protect itself and reduce the voltage to maintain the 2A limit. If this protection was not available, the power supply would just die. Your argument is this is a 10Watt supply, so if you drop the voltage to 0.1V, you can achieve 100A make no sense whatsoever. The maximum current is defined by the size of the wire in the coil or transformer and the size of the PCB traces. To prevent exceeding this max current, the regulator will reduce the voltage and maintain a constant current, thereby protecting the power supply from a dangerous failure. 

Regards,

John

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[Przemek Klosowski]

On Mon, Jul 4, 2016 at 9:14 PM, 'Morgaine' via BeagleBoard
<beagl...@googlegroups.com> wrote:
> John Syne writes:
>>
>> > a power supply that is spec’d at 4A should not shutdown when it sees a
>> > 4A load, but rather, it should current limit at 4A. If the power supply is
>> > spec’d at 4A, then 4A should not be treated as a short circuit.
>
>
> That's impossible. You can't recommend that fundamental electrical laws be
> overridden. :P
>
> If a PSU current limits at 4A, it can do so only by reducing its output
> voltage. This may then drop below specification for its load and this can
> have very bad consequences such as non-stop rebooting. There is no way for
> the voltage to be maintained above its minimum spec while still providing a
> current limit.

Yes, but remember that the problem here is a startup inrush current,
which would be handled properly by current limiting. After all, that's
what the 2A current supply is doing: essentially, it soft-starts,
providing limited current charging the input caps, while ramping up
the voltage. Once the caps are charged and the supply voltage
stabilizes at the nominal value, the system progresses to boot.

[Harvey White]

Your discussion makes the assumption that the power supply provided or
specified is current limited at the maximum output current. I
(without looking at PS specs) have no such assurance.

*with* such limiting, behavior is one way. Without that limiting,
behavior is quite something else.

I don't remember (particularly...) that the power supply specification
mentioned current limiting. I thought that I had read only a voltage
tolerance. People on this forum have mentioned using a particular
supply (not model number, simply rating). The normal problem I have
seen was the current supply rating, so that the BBB could boot as well
as have sufficient power to drive such things as hard drives.

It seems to me that this does not address the *maximum* current of the
supply, nor does it specify what kind of supply is expected to supply
that maximum.

If this current capacity (as in surge current or current limiting) is
a difficulty, then perhaps it needs to be addressed. I have not seen
(nor particularly searched for....) such limitations.

*if* they are important, then they need to be mentioned. If they are
not, then perhaps that needs to be mentioned as well.

Harvey

[John Syne]

You know that you are nit picking right now. The requirements are clear, 5V2A. Test any of these supplies, and see what happens to the supply when you try to take 3A, it won’t and it will current limit at close to 2A. For UL requirements, they all have short circuit protection, which is a safety requirement. Most of these supplies are based on switchmode technologies and hence naturally current limit. This is just common sense, and so why do you expect Gerald to specify every detail. The documentation he compiled is very detailed so I would cut him some slack here.

Here is the recommended power supplies:

http://elinux.org/Beagleboard:BeagleBone_Black_Accessories#Power_Supplies

Here is what is described on the BeagleBoard FAQ

What power peripherals are required/desirable?
• There are several ways to power a Beagle. The option exists to feed the on-board regulators through either the 5V barrel connector input or USB input. When powered up over USB, the regulators are somewhat limited in what they can supply the system. Power over USB is sufficient as long as the software and system running perform some management to keep it under the USB current limit threshold. For simplicity and maximum capability, powering over the 5V barrel connector is typically recommended.
• The power adapter is required to provide 5V over a 5.5mm outer diameter and 2.1mm inner diameter barrel connector (a barrel connector length of 9.5mm is more than sufficient). The recommended supply current is at least 1.2A (or 6W), but at least 2A (or 10W) is recommended if you are going to connect up anything over the USB. The actual power consumption will vary greatly with changes on the USB load.

Regards,
John

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[kzsolt...@gmail.com]

John, thank you for your feedback!

Looks like the central question what is the "correct power supply", moreover what is the standard to protect from overcurrent by power supply.

1). Oldest method is: fuse.

2). Old method is: if the load heavy than power supply capability then limit current to maximum (decrease output voltage).

3). if the load heavy than power supply capability then decrease output voltage using diffrent characteristic.

4). If power supply detect overcurrent, then switch of output voltage for specifyed time and then try it again.

Next question is: how long overcurrent is overcurrent?

a). Overcurrent for 1ms? 

b). Overcurrent for 100ms? 

c). Overcurrent for 1s?

Present method used by BBB is match just for power suppy which use method 2b and c.

That is why I say, moving "CAP" from TPS2051 IN to OUT make board compatible power suppy which use method 1-4 (near all).

But the main probelm is: manufacturers not specify what is the current protection method for its power supply. Therefore you cannot select "correct power supply" which use method 2.

Othersides I understand your cost problem. But current board has enough space to place one more 10uF 10V capacitor (see C7, C8, C10, C13). And it is cost less than 0,01USD. I think is this worh for mouch wide power supply compatbility.

[John Syne]

You need to think through the complete problem. Sure you can move the 100uF capacitor to the other side of TPS2051, but you still need a bulk capacitor on the IN side because of HDMI and VIO requirements. The peak current is based on the capacitor ESR and not the size of the capacitor. The size of the capacitor affects the duration of the peak current. So, given that you still need a bulk capacitor on the TPS2051 IN side, you have achieved little by moving some of capacitance to the TPS2051 OUT side. Also, cost of component is only one part of the total cost. Carrying additional inventory, cost of placement, engineering changes, testing, managing another version, can sometimes be far higher than the cost of the component. Anyway, even doing what you asked for will do little to reduce the peak current, so why go through the exercise. Doesn’t make sense to me. 

Regards,

John

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