Re: [beagleboard] Re: BBB startup current

[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.

On Mon, Jul 4, 2016 at 9:38 PM, 'Mark Lazarewicz' via BeagleBoard <
beagleboard@googlegroups.com> wrote:

> :-) 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
> 
>
> On Mon, Jul 4, 2016 at 4:11 PM, William Hermans
>  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 
> wrote:
>
>> Thank you for your feedback.
>>
>> Gerald
>>
>> On Mon, Jul 4, 2016 at 3:18 PM,  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.
>>>
>>> --
>>> For more options, visit http://beagleboard.org/discuss
>>> ---
>>> You received this message because you are subscribed to the Google
>>> Groups "BeagleBoard" group.
>>> To unsubscribe from this group and stop receiving emails from it, send
>>> an email to beagleboard+unsubscr...@googlegroups.com.
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>>> https://groups.google.com/d/msgid/beagleboard/b974f98a-0cff-4380-af1f-9ce5db9e199f%40googlegroups.com
>>> 
>>> .
>>>
>>> For more options, visit https://groups.google.com/d/optout.
>>>
>>
>>
>>
>> --
>> Gerald
>>
>> ger...@beagleboard.org
>> http://beagleboard.org/
>> gcol...@emprodesign.com
>>
>> --
>> For more options, visit http://beagleboard.org/discuss
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>> 
>> .
>>
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>>
>
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Re: [beagleboard] Re: BBB startup current

['Mark Lazarewicz' via BeagleBoard]

:-) 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 
 
  On Mon, Jul 4, 2016 at 4:11 PM, William Hermans 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  wrote:

Thank you for your feedback. 
Gerald
On Mon, Jul 4, 2016 at 3:18 PM,  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 gerald@beagleboard.orghttp://beagleboard.org/gcol...@emprodesign.com


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Re: [beagleboard] Re: BBB startup current

[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.

On Mon, Jul 4, 2016 at 1:55 PM, Gerald Coley  wrote:

> Thank you for your feedback.
>
> Gerald
>
> On Mon, Jul 4, 2016 at 3:18 PM,  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.
>>
>> --
>> For more options, visit http://beagleboard.org/discuss
>> ---
>> You received this message because you are subscribed to the Google Groups
>> "BeagleBoard" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
>> email to beagleboard+unsubscr...@googlegroups.com.
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>> https://groups.google.com/d/msgid/beagleboard/b974f98a-0cff-4380-af1f-9ce5db9e199f%40googlegroups.com
>> 
>> .
>>
>> For more options, visit https://groups.google.com/d/optout.
>>
>
>
>
> --
> Gerald
>
> ger...@beagleboard.org
> http://beagleboard.org/
> gcol...@emprodesign.com
>
> --
> For more options, visit http://beagleboard.org/discuss
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> 
> .
>
> For more options, visit https://groups.google.com/d/optout.
>

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Re: [beagleboard] Re: BBB startup current

[Gerald Coley]

Thank you for your feedback.

Gerald

On Mon, Jul 4, 2016 at 3:18 PM,  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.
>
> --
> For more options, visit http://beagleboard.org/discuss
> ---
> You received this message because you are subscribed to the Google Groups
> "BeagleBoard" group.
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> email to beagleboard+unsubscr...@googlegroups.com.
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> 
> .
>
> For more options, visit https://groups.google.com/d/optout.
>



-- 
Gerald

ger...@beagleboard.org
http://beagleboard.org/
gcol...@emprodesign.com

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Re: [beagleboard] Re: BBB startup current

[kzsoltkzsolt]

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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Re: [beagleboard] Re: BBB startup current

[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

On Sun, Jul 3, 2016 at 7:02 AM,  wrote:

> "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.
>
> --
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-- 
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http://beagleboard.org/
gcol...@emprodesign.com

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Re: [beagleboard] Re: BBB startup current

[kzsoltkzsolt]

"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. 

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Re: [beagleboard] Re: BBB startup current

[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

On Sat, Jul 2, 2016 at 8:26 AM,  wrote:

> 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.
>
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-- 
Gerald

ger...@beagleboard.org
http://beagleboard.org/
gcol...@emprodesign.com

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Re: [beagleboard] Re: BBB startup current

[kzsoltkzsolt]

 

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.  

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Re: [beagleboard] Re: BBB startup current

[Gerald Coley]

Sounds like you have it figured out.

Gerald

On Thu, Jun 30, 2016 at 3:23 PM,  wrote:

> 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.
>
>
>
>
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-- 
Gerald

ger...@beagleboard.org
http://beagleboard.org/
gcol...@emprodesign.com

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