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From: E on 21 Feb 2010 12:11

"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> kirjoitti
viestiss�:iro0o5hmfbejuo9lt3udkodidv4nitjd1m(a)4ax.com...
>>>
>>
>>The internal schematics of classics like LM317 and LM1117 and such are
>>on the data sheets. Some people (?) could deduce their behavior from
>>that.
>>
>>John
>
> Those aren't LDO's, they're NPN "followers"; not PNP or PMOS, whose
> behavior would be radically different, and quite process dependent.
>

LP2950 has schematics on datasheet (National version).

-ek


From: Jim Thompson on 21 Feb 2010 12:29
On Sun, 21 Feb 2010 19:11:51 +0200, "E" <invalid(a)invalid.invalid>
wrote:

>
>"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> kirjoitti
>viestiss�:iro0o5hmfbejuo9lt3udkodidv4nitjd1m(a)4ax.com...
>>>>
>>>
>>>The internal schematics of classics like LM317 and LM1117 and such are
>>>on the data sheets. Some people (?) could deduce their behavior from
>>>that.
>>>
>>>John
>>
>> Those aren't LDO's, they're NPN "followers"; not PNP or PMOS, whose
>> behavior would be radically different, and quite process dependent.
>>
>
>LP2950 has schematics on datasheet (National version).
>
>-ek
>

Thanks! I'll check that out. Although my past experiences in the
"jelly bean" business is those schematics are usually "simplified" to
hide IP.

This is getting to be a really amusing mental endeavor! For instance,
how might an LM7805 behave with a zener inserted in its ground lead to
boost the voltage ?:-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
From: Jim Thompson on 21 Feb 2010 12:37
On Sun, 21 Feb 2010 19:11:51 +0200, "E" <invalid(a)invalid.invalid>
wrote:

>
>"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> kirjoitti
>viestiss�:iro0o5hmfbejuo9lt3udkodidv4nitjd1m(a)4ax.com...
>>>>
>>>
>>>The internal schematics of classics like LM317 and LM1117 and such are
>>>on the data sheets. Some people (?) could deduce their behavior from
>>>that.
>>>
>>>John
>>
>> Those aren't LDO's, they're NPN "followers"; not PNP or PMOS, whose
>> behavior would be radically different, and quite process dependent.
>>
>
>LP2950 has schematics on datasheet (National version).
>
>-ek
>

Thanks! Looks good!

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
From: mike on 21 Feb 2010 13:15
Jim Thompson wrote:
> This rainy afternoon (East-coasters beware, that usually spells more
> snow for you), I was amusing myself trying to behavioral model a
> voltage regulator when you hit drop-out.
>
> Then I realized, I've never designed an integrated voltage regulator
> for general use, only those inside ASIC's where I can control all the
> conditions.
>
> Thus I'm clueless of behavior of commercial offerings at or below VDO.
>
> I'm guessing that output voltage drops linearly with VIN once the
> drop-out point is hit??
>
> But what about current capability? Does it drop sharply, linearly, or
> linearly to some critical point then drop like a rock.
>
> Pointers/data appreciated!
>
> Thanks!
>
> ...Jim Thompson

What are your assumptions about the source?
A battery going flat might induce limit-cycle oscillations
that wouldn't show up with a stiff source?? or not...
From: Jim Thompson on 21 Feb 2010 13:41
On Sun, 21 Feb 2010 10:15:31 -0800, mike <spamme0(a)go.com> wrote:

>Jim Thompson wrote:
>> This rainy afternoon (East-coasters beware, that usually spells more
>> snow for you), I was amusing myself trying to behavioral model a
>> voltage regulator when you hit drop-out.
>>
>> Then I realized, I've never designed an integrated voltage regulator
>> for general use, only those inside ASIC's where I can control all the
>> conditions.
>>
>> Thus I'm clueless of behavior of commercial offerings at or below VDO.
>>
>> I'm guessing that output voltage drops linearly with VIN once the
>> drop-out point is hit??
>>
>> But what about current capability? Does it drop sharply, linearly, or
>> linearly to some critical point then drop like a rock.
>>
>> Pointers/data appreciated!
>>
>> Thanks!
>>
>> ...Jim Thompson
>
>What are your assumptions about the source?
>A battery going flat might induce limit-cycle oscillations
>that wouldn't show up with a stiff source?? or not...

From my modeling point of view, the "source" is just "something"
connected to the "IN" terminal.

BUT, The way I am envisioning the model, a flaky source, if you have a
model for it, would induce the very behavior you want to see.

Maybe model "source" as a voltage source with a parameterized
impedance rise?

Or get out a battery manual and model "Charge", a parameter that
reflects both voltage and impedance effects?

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
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