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Simple LDO regualtor
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David Eather
Oct 5, 2012, 7:31:04 AM10/5/12
to
I'm just asking what smart people would use for a simple low drop out
regulator (3.3v out) low quiescent current a bonus but I am more
interested in devices with fewer pins (like 3 if possible). I want a
regulated 3.3v for a uP that will mostly be asleep (but the peripherals
will gobble power when energized hence what is wasted by the reg is pretty
much unimportant). It has to be able to run from 4v or as close to it as
possible.
TIA
regulator (3.3v out) low quiescent current a bonus but I am more
interested in devices with fewer pins (like 3 if possible). I want a
regulated 3.3v for a uP that will mostly be asleep (but the peripherals
will gobble power when energized hence what is wasted by the reg is pretty
much unimportant). It has to be able to run from 4v or as close to it as
possible.
TIA
Spehro Pefhany
Oct 5, 2012, 8:04:27 AM10/5/12
to
has horrible quiescent current consumption (worse than a 78xx series).
The LP2951 has reasonably low Iq and is popular, but it's a bit fussy
about the output cap characteristics.
(with most all LDOs and many negative regulators, read the section on
output caps with great interest, then read it again and don't go near
the limits).
You could try Diodes' AP7313 which looks to me like some Asian ones.
<100uA Iq and stable with an appropriate-size ceramic output cap.
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
lang...@fonz.dk
Oct 5, 2012, 8:32:40 AM10/5/12
to
it is right in the sweet spot for battery stuff, liion battery
is 3.6-4.2V
-Lasse
Jan Panteltje
Oct 5, 2012, 9:03:31 AM10/5/12
to
On a sunny day (Fri, 5 Oct 2012 05:32:40 -0700 (PDT)) it happened
"lang...@fonz.dk" <lang...@fonz.dk> wrote in
<85f1669d-70d5-4fe1...@y6g2000vbb.googlegroups.com>:
>On 5 Okt., 13:30, "David Eather" <eat...@tpg.com.au> wrote:
>> I'm just asking what smart people would use for a simple low drop out
>> regulator (3.3v out) low quiescent current a bonus but I am more
>> interested in devices with fewer pins (like 3 if possible). I want a
>> regulated 3.3v for a uP that will mostly be asleep (but the peripheral=
>s
>> will gobble power when energized hence what is wasted by the reg is prett=
>
>-Lasse
>
"lang...@fonz.dk" <lang...@fonz.dk> wrote in
<85f1669d-70d5-4fe1...@y6g2000vbb.googlegroups.com>:
>On 5 Okt., 13:30, "David Eather" <eat...@tpg.com.au> wrote:
>> I'm just asking what smart people would use for a simple low drop out
>> regulator (3.3v out) low quiescent current a bonus but I am more
>> interested in devices with fewer pins (like 3 if possible). I want a
>s
>> will gobble power when energized hence what is wasted by the reg is prett=
>y
>> much unimportant). It has to be able to run from 4v or as close to it as
>> possible.
>>
>> TIA
>
>there should be tons to choose from from from all of the usuals
>it is right in the sweet spot for battery stuff, liion battery
>is 3.6-4.2V
If the 4V is stabilised, just use a si diode drop, that makes 3.3V.
>> much unimportant). It has to be able to run from 4v or as close to it as
>> possible.
>>
>> TIA
>
>there should be tons to choose from from from all of the usuals
>it is right in the sweet spot for battery stuff, liion battery
>is 3.6-4.2V
>
>-Lasse
>
John Larkin
Oct 5, 2012, 10:37:49 AM10/5/12
to
On Fri, 05 Oct 2012 08:04:27 -0400, Spehro Pefhany
<spef...@interlogDOTyou.knowwhat> wrote:
>On Fri, 05 Oct 2012 21:31:04 +1000, the renowned "David Eather"
><eat...@tpg.com.au> wrote:
>
>>I'm just asking what smart people would use for a simple low drop out
>>regulator (3.3v out) low quiescent current a bonus but I am more
>>interested in devices with fewer pins (like 3 if possible). I want a
>>regulated 3.3v for a uP that will mostly be asleep (but the peripherals
>>will gobble power when energized hence what is wasted by the reg is pretty
>>much unimportant). It has to be able to run from 4v or as close to it as
>>possible.
>>
>>TIA
>
>Some rough specs would help. The LM1117 is the most common LDO, but it
>has horrible quiescent current consumption (worse than a 78xx series).
1117 is an "MDO", a little better than an LM317 but not much. It
<spef...@interlogDOTyou.knowwhat> wrote:
>On Fri, 05 Oct 2012 21:31:04 +1000, the renowned "David Eather"
><eat...@tpg.com.au> wrote:
>
>>I'm just asking what smart people would use for a simple low drop out
>>regulator (3.3v out) low quiescent current a bonus but I am more
>>interested in devices with fewer pins (like 3 if possible). I want a
>>regulated 3.3v for a uP that will mostly be asleep (but the peripherals
>>will gobble power when energized hence what is wasted by the reg is pretty
>>much unimportant). It has to be able to run from 4v or as close to it as
>>possible.
>>
>>TIA
>
>Some rough specs would help. The LM1117 is the most common LDO, but it
>has horrible quiescent current consumption (worse than a 78xx series).
wouldn't make 3.3 from 4. It also won't make 2.5 from 3.3... trust me
on that.
LP2985IM5-3.3 is nice: sot23, and works with very low ESR caps, namely
a big ceramic. 150 mA max.
Here's my fix for trying to get 2.5 from 3.3 with an LM1117:
https://dl.dropbox.com/u/53724080/Circuits/Diode.jpg
That's a melf zener used in the forward direction. Worked great.
--
John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
hamilton
Oct 5, 2012, 11:23:52 AM10/5/12
to
50 ma, 100 ma, 150 ma ??
TC1014/TC1015/TC1185
http://ww1.microchip.com/downloads/en/DeviceDoc/21335e.pdf
"very low dropout voltage,
typically 85 mV (TC1014), 180 mV (TC1015), and 270 mV (TC1185) at
full-load."
TTman
Oct 5, 2012, 11:40:03 AM10/5/12
to
"David Eather" <eat...@tpg.com.au> wrote in message
news:op.wlpd92zbwei6gd@phenom-pc...
Nico Coesel
Oct 5, 2012, 12:42:34 PM10/5/12
to
current. A few years ago I fitted 3.3V memory modules in 5V slots. It
turned out I needed to put 2 diodes in series to get somewhere between
3V and 4V (which was perfectly in range for the memory chips).
--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico@nctdevpuntnl (punt=.)
--------------------------------------------------------------
lang...@fonz.dk
Oct 5, 2012, 12:53:28 PM10/5/12
to
On 5 Okt., 18:42, n...@puntnl.niks (Nico Coesel) wrote:
> ><85f1669d-70d5-4fe1-866e-16d8fa93c...@y6g2000vbb.googlegroups.com>:
when the mcu goes to sleep and uses tens of microamps instead you
might
get i trouble
-Lasse
> Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
> >On a sunny day (Fri, 5 Oct 2012 05:32:40 -0700 (PDT)) it happened
> >"langw...@fonz.dk" <langw...@fonz.dk> wrote in
> >On a sunny day (Fri, 5 Oct 2012 05:32:40 -0700 (PDT)) it happened
> ><85f1669d-70d5-4fe1-866e-16d8fa93c...@y6g2000vbb.googlegroups.com>:
>
> >>On 5 Okt., 13:30, "David Eather" <eat...@tpg.com.au> wrote:
> >>> I'm just asking what smart people would use for a simple low drop out
> >>> regulator (3.3v out) low quiescent current a bonus but I am more
> >>> interested in devices with fewer pins (like 3 if possible). I want a
> >>> regulated 3.3v for a uP that will mostly be asleep (but the peripheral=
> >>s
> >>> will gobble power when energized hence what is wasted by the reg is prett=
> >>y
> >>> much unimportant). It has to be able to run from 4v or as close to it as
> >>> possible.
>
> >>> TIA
>
> >>there should be tons to choose from from from all of the usuals
> >>it is right in the sweet spot for battery stuff, liion battery
> >>is 3.6-4.2V
>
> >If the 4V is stabilised, just use a si diode drop, that makes 3.3V.
>
> Actually that is a bad idea. The voltage drop depends largely on the
> current. A few years ago I fitted 3.3V memory modules in 5V slots. It
> turned out I needed to put 2 diodes in series to get somewhere between
> 3V and 4V (which was perfectly in range for the memory chips).
>
yep, probably be fine if you use tens of milliamps all the time, but
> >>On 5 Okt., 13:30, "David Eather" <eat...@tpg.com.au> wrote:
> >>> I'm just asking what smart people would use for a simple low drop out
> >>> regulator (3.3v out) low quiescent current a bonus but I am more
> >>> interested in devices with fewer pins (like 3 if possible). I want a
> >>> regulated 3.3v for a uP that will mostly be asleep (but the peripheral=
> >>s
> >>> will gobble power when energized hence what is wasted by the reg is prett=
> >>y
> >>> much unimportant). It has to be able to run from 4v or as close to it as
> >>> possible.
>
> >>> TIA
>
> >>there should be tons to choose from from from all of the usuals
> >>it is right in the sweet spot for battery stuff, liion battery
> >>is 3.6-4.2V
>
> >If the 4V is stabilised, just use a si diode drop, that makes 3.3V.
>
> Actually that is a bad idea. The voltage drop depends largely on the
> current. A few years ago I fitted 3.3V memory modules in 5V slots. It
> turned out I needed to put 2 diodes in series to get somewhere between
> 3V and 4V (which was perfectly in range for the memory chips).
>
when the mcu goes to sleep and uses tens of microamps instead you
might
get i trouble
-Lasse
Jan Panteltje
Oct 5, 2012, 1:53:04 PM10/5/12
to
On a sunny day (Fri, 05 Oct 2012 16:42:34 GMT) it happened ni...@puntnl.niks
(Nico Coesel) wrote in <506f0d4e....@news.kpn.nl>:
>Jan Panteltje <pNaonSt...@yahoo.com> wrote:
>
>>On a sunny day (Fri, 5 Oct 2012 05:32:40 -0700 (PDT)) it happened
>>"lang...@fonz.dk" <lang...@fonz.dk> wrote in
>><85f1669d-70d5-4fe1...@y6g2000vbb.googlegroups.com>:
>>
>>>On 5 Okt., 13:30, "David Eather" <eat...@tpg.com.au> wrote:
>>>> I'm just asking what smart people would use for a simple low drop out
>>>> regulator (3.3v out) low quiescent current a bonus but I am more
>>>> interested in devices with fewer pins (like 3 if possible). ï¿œI want a
>>>> regulated 3.3v ï¿œfor a uP that will mostly be asleep (but the peripheral=
(Nico Coesel) wrote in <506f0d4e....@news.kpn.nl>:
>Jan Panteltje <pNaonSt...@yahoo.com> wrote:
>
>>On a sunny day (Fri, 5 Oct 2012 05:32:40 -0700 (PDT)) it happened
>>"lang...@fonz.dk" <lang...@fonz.dk> wrote in
>><85f1669d-70d5-4fe1...@y6g2000vbb.googlegroups.com>:
>>
>>>On 5 Okt., 13:30, "David Eather" <eat...@tpg.com.au> wrote:
>>>> I'm just asking what smart people would use for a simple low drop out
>>>> regulator (3.3v out) low quiescent current a bonus but I am more
>>>> regulated 3.3v ï¿œfor a uP that will mostly be asleep (but the peripheral=
>>>s
>>>> will gobble power when energized hence what is wasted by the reg is prett=
>>>y
>>>> much unimportant). It has to be able to run from 4v or as close to it as
>>>> possible.
>>>>
>>>> TIA
>>>
>>>there should be tons to choose from from from all of the usuals
>>>it is right in the sweet spot for battery stuff, liion battery
>>>is 3.6-4.2V
>>
>>If the 4V is stabilised, just use a si diode drop, that makes 3.3V.
>
>Actually that is a bad idea. The voltage drop depends largely on the
>current. A few years ago I fitted 3.3V memory modules in 5V slots. It
>turned out I needed to put 2 diodes in series to get somewhere between
>3V and 4V (which was perfectly in range for the memory chips).
Yes, it depends, as he gives no current values or tolerance the answer is correct.
>>>> will gobble power when energized hence what is wasted by the reg is prett=
>>>y
>>>> much unimportant). It has to be able to run from 4v or as close to it as
>>>> possible.
>>>>
>>>> TIA
>>>
>>>there should be tons to choose from from from all of the usuals
>>>it is right in the sweet spot for battery stuff, liion battery
>>>is 3.6-4.2V
>>
>>If the 4V is stabilised, just use a si diode drop, that makes 3.3V.
>
>Actually that is a bad idea. The voltage drop depends largely on the
>current. A few years ago I fitted 3.3V memory modules in 5V slots. It
>turned out I needed to put 2 diodes in series to get somewhere between
>3V and 4V (which was perfectly in range for the memory chips).
Spehro Pefhany
Oct 5, 2012, 2:59:35 PM10/5/12
to
On Fri, 05 Oct 2012 07:37:49 -0700, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>1117 is an "MDO", a little better than an LM317 but not much. It
>wouldn't make 3.3 from 4. It also won't make 2.5 from 3.3... trust me
>on that.
Yup, and the data sheet says that too. Even at zero current it
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>1117 is an "MDO", a little better than an LM317 but not much. It
>wouldn't make 3.3 from 4. It also won't make 2.5 from 3.3... trust me
>on that.
typically needs about a volt, and, extrapolating from the curve, maybe
1.1V typical at zero current and -40°C. "MDO" indeed.
John Larkin
Oct 5, 2012, 3:13:24 PM10/5/12
to
no resistors. For FPGA supplies.
--
John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
David Eather
Oct 5, 2012, 3:30:38 PM10/5/12
to
David Eather
Oct 5, 2012, 3:37:49 PM10/5/12
to
again!
David Eather
Oct 5, 2012, 3:46:41 PM10/5/12
to
David Eather
Oct 5, 2012, 3:46:25 PM10/5/12
to
David Eather
Oct 5, 2012, 3:47:19 PM10/5/12
to
David Eather
Oct 6, 2012, 11:51:36 AM10/6/12
to
bypassing (thanks for that hint too).
John Fields
Oct 7, 2012, 5:04:47 PM10/7/12
to
A little late, too expensive, and way more than 3 pins, but just for
grins:
Version 4
SHEET 1 880 680
WIRE -240 -16 -384 -16
WIRE 16 -16 -240 -16
WIRE 224 -16 16 -16
WIRE -240 16 -240 -16
WIRE 224 96 224 -16
WIRE 16 112 16 -16
WIRE -240 128 -240 96
WIRE -16 128 -240 128
WIRE 64 144 48 144
WIRE 160 144 144 144
WIRE -16 160 -64 160
WIRE -64 256 -64 160
WIRE 64 256 -64 256
WIRE 224 256 224 192
WIRE 224 256 144 256
WIRE -384 272 -384 -16
WIRE -240 272 -240 128
WIRE 224 288 224 256
WIRE -64 304 -64 256
WIRE -384 416 -384 352
WIRE -240 416 -240 336
WIRE -240 416 -384 416
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WIRE -64 416 -240 416
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WIRE 224 416 16 416
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SYMATTR SpiceLine ""
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SYMATTR InstName V1
SYMBOL pnp 160 192 M180
SYMATTR InstName Q1
SYMATTR Value 2N3906
SYMBOL res 48 240 M90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
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SYMATTR Value 10k
SYMATTR SpiceLine ""
SYMBOL res -80 288 R0
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WINDOW 3 -72 62 Left 2
SYMATTR InstName R3
SYMATTR Value 31250
SYMATTR SpiceLine ""
SYMBOL Opamps\\LTC1050 16 80 R0
WINDOW 0 -104 -6 Left 2
WINDOW 3 -136 25 Left 2
SYMATTR InstName U1
SYMBOL References\\LT1634-2.5 -240 304 R0
WINDOW 3 12 -45 Left 2
WINDOW 0 15 -76 Left 2
SYMATTR InstName U2
SYMBOL res -256 0 R0
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SYMATTR Value 15K
SYMATTR SpiceLine ""
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WINDOW 3 32 56 VTop 2
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SYMATTR Value 100
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TEXT -376 440 Left 2 !.tran .02
--
JF
John Larkin
Oct 7, 2012, 7:50:35 PM10/7/12
to
On Sun, 07 Oct 2012 16:04:47 -0500, John Fields
<jfi...@austininstruments.com> wrote:
>On Fri, 05 Oct 2012 21:31:04 +1000, "David Eather" <eat...@tpg.com.au>
>wrote:
>
>>I'm just asking what smart people would use for a simple low drop out
>>regulator (3.3v out) low quiescent current a bonus but I am more
>>interested in devices with fewer pins (like 3 if possible). I want a
>>regulated 3.3v for a uP that will mostly be asleep (but the peripherals
>>will gobble power when energized hence what is wasted by the reg is pretty
>>much unimportant). It has to be able to run from 4v or as close to it as
>>possible.
>>
>>TIA
>
>---
>A little late, too expensive, and way more than 3 pins, but just for
>grins:
You're right, that's hilarious! Try adding a little load capacitance.
<jfi...@austininstruments.com> wrote:
>On Fri, 05 Oct 2012 21:31:04 +1000, "David Eather" <eat...@tpg.com.au>
>wrote:
>
>>I'm just asking what smart people would use for a simple low drop out
>>regulator (3.3v out) low quiescent current a bonus but I am more
>>interested in devices with fewer pins (like 3 if possible). I want a
>>regulated 3.3v for a uP that will mostly be asleep (but the peripherals
>>will gobble power when energized hence what is wasted by the reg is pretty
>>much unimportant). It has to be able to run from 4v or as close to it as
>>possible.
>>
>>TIA
>
>---
>A little late, too expensive, and way more than 3 pins, but just for
>grins:
--
John Larkin Highland Technology Inc
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Photonics and fiberoptic TTL data links
John Fields
Oct 8, 2012, 3:24:09 PM10/8/12
to
On Sun, 07 Oct 2012 16:50:35 -0700, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>On Sun, 07 Oct 2012 16:04:47 -0500, John Fields
><jfi...@austininstruments.com> wrote:
>
>>On Fri, 05 Oct 2012 21:31:04 +1000, "David Eather" <eat...@tpg.com.au>
>>wrote:
>>
>>>I'm just asking what smart people would use for a simple low drop out
>>>regulator (3.3v out) low quiescent current a bonus but I am more
>>>interested in devices with fewer pins (like 3 if possible). I want a
>>>regulated 3.3v for a uP that will mostly be asleep (but the peripherals
>>>will gobble power when energized hence what is wasted by the reg is pretty
>>>much unimportant). It has to be able to run from 4v or as close to it as
>>>possible.
>>>
>>>TIA
>>
>>---
>>A little late, too expensive, and way more than 3 pins, but just for
>>grins:
>
>
>You're right, that's hilarious! Try adding a little load capacitance.
---
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>On Sun, 07 Oct 2012 16:04:47 -0500, John Fields
><jfi...@austininstruments.com> wrote:
>
>>On Fri, 05 Oct 2012 21:31:04 +1000, "David Eather" <eat...@tpg.com.au>
>>wrote:
>>
>>>I'm just asking what smart people would use for a simple low drop out
>>>regulator (3.3v out) low quiescent current a bonus but I am more
>>>interested in devices with fewer pins (like 3 if possible). I want a
>>>regulated 3.3v for a uP that will mostly be asleep (but the peripherals
>>>will gobble power when energized hence what is wasted by the reg is pretty
>>>much unimportant). It has to be able to run from 4v or as close to it as
>>>possible.
>>>
>>>TIA
>>
>>---
>>A little late, too expensive, and way more than 3 pins, but just for
>>grins:
>
>
>You're right, that's hilarious! Try adding a little load capacitance.
Why?
To make it oscillate?
Stop that from happening like this:
Version 4
SHEET 1 880 680
WIRE -240 -16 -384 -16
WIRE 16 -16 -240 -16
WIRE 224 -16 16 -16
WIRE -240 16 -240 -16
WIRE 224 96 224 -16
WIRE 16 112 16 -16
WIRE -240 128 -240 96
WIRE -16 128 -240 128
WIRE 64 144 48 144
WIRE 160 144 144 144
WIRE -16 160 -64 160
WIRE 304 240 224 240
WIRE 336 240 304 240
WIRE -64 256 -64 160
WIRE 48 256 -64 256
WIRE 64 256 48 256
WIRE 160 256 144 256
WIRE 224 256 224 240
WIRE 224 256 160 256
WIRE -384 272 -384 -16
WIRE -240 272 -240 128
WIRE -240 272 -240 128
WIRE -64 304 -64 256
WIRE 224 304 224 256
WIRE 304 304 304 240
WIRE 48 336 48 256
WIRE 80 336 48 336
WIRE 160 336 160 256
WIRE 160 336 144 336
WIRE -384 416 -384 352
WIRE -240 416 -240 336
WIRE -240 416 -384 416
WIRE -64 416 -64 384
WIRE -64 416 -240 416
WIRE 16 416 16 176
WIRE 16 416 -64 416
WIRE 224 416 224 384
WIRE -240 416 -240 336
WIRE -240 416 -384 416
WIRE -64 416 -64 384
WIRE -64 416 -240 416
WIRE 16 416 16 176
WIRE 16 416 -64 416
WIRE 224 416 16 416
WIRE 304 416 304 368
WIRE 304 416 224 416
WIRE -384 464 -384 416
FLAG -384 464 0
FLAG 336 240 Vout
FLAG -384 464 0
SYMBOL res 208 288 R0
WINDOW 0 65 33 VBottom 2
WINDOW 3 64 35 VTop 2
SYMATTR InstName C1
SYMATTR Value 1n
SYMATTR SpiceLine ""
SYMBOL cap 288 304 R0
SYMATTR InstName C2
SYMATTR Value 1000µ
SYMATTR SpiceLine ""
TEXT -376 440 Left 2 !.tran .1
--
JF
John S
Oct 9, 2012, 2:10:49 PM10/9/12
to
On 10/8/2012 2:24 PM, John Fields wrote:
> On Sun, 07 Oct 2012 16:50:35 -0700, John Larkin
> <jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>> On Sun, 07 Oct 2012 16:04:47 -0500, John Fields
>> <jfi...@austininstruments.com> wrote:
>>
>>> On Fri, 05 Oct 2012 21:31:04 +1000, "David Eather" <eat...@tpg.com.au>
>>> wrote:
>>>
>>>> I'm just asking what smart people would use for a simple low drop out
>>>> regulator (3.3v out) low quiescent current a bonus but I am more
>>>> interested in devices with fewer pins (like 3 if possible). I want a
>>>> regulated 3.3v for a uP that will mostly be asleep (but the peripherals
>>>> will gobble power when energized hence what is wasted by the reg is pretty
>>>> much unimportant). It has to be able to run from 4v or as close to it as
>>>> possible.
>>>>
>>>> TIA
>>>
>>> ---
>>> A little late, too expensive, and way more than 3 pins, but just for
>>> grins:
>>
>>
>> You're right, that's hilarious! Try adding a little load capacitance.
>
> ---
> Why?
>
> To make it oscillate?
>
> Stop that from happening like this:
Hey, John -
> On Sun, 07 Oct 2012 16:50:35 -0700, John Larkin
> <jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>> On Sun, 07 Oct 2012 16:04:47 -0500, John Fields
>> <jfi...@austininstruments.com> wrote:
>>
>>> On Fri, 05 Oct 2012 21:31:04 +1000, "David Eather" <eat...@tpg.com.au>
>>> wrote:
>>>
>>>> I'm just asking what smart people would use for a simple low drop out
>>>> regulator (3.3v out) low quiescent current a bonus but I am more
>>>> interested in devices with fewer pins (like 3 if possible). I want a
>>>> regulated 3.3v for a uP that will mostly be asleep (but the peripherals
>>>> will gobble power when energized hence what is wasted by the reg is pretty
>>>> much unimportant). It has to be able to run from 4v or as close to it as
>>>> possible.
>>>>
>>>> TIA
>>>
>>> ---
>>> A little late, too expensive, and way more than 3 pins, but just for
>>> grins:
>>
>>
>> You're right, that's hilarious! Try adding a little load capacitance.
>
> ---
> Why?
>
> To make it oscillate?
>
> Stop that from happening like this:
Change C2 to 1nF and...
Change your simulation to:
.tran 0 .1 0 10u
I don't know whether it's an artifact of simulation or not having a
small enough step to see what's going on.
Not trying to be argumentative.
John S
John S
Oct 9, 2012, 2:29:38 PM10/9/12
to
It seems to work better in LTSpice if R5 is changed to 3.3k.
What do you think?
John S
John S
Oct 9, 2012, 2:35:34 PM10/9/12
to
sine wave generator. Sorry about not considering all the possibilities.
John S
John Fields
Oct 10, 2012, 4:09:06 AM10/10/12
to
On Tue, 09 Oct 2012 13:10:49 -0500, John S <Sop...@invalid.org>
wrote:
---
Thanks, John.
With C2 equal to a minimum of 100湩, it looks like the output gets
stable pretty quick.
--
JF
wrote:
Thanks, John.
With C2 equal to a minimum of 100湩, it looks like the output gets
stable pretty quick.
--
JF
John S
Oct 11, 2012, 4:13:18 PM10/11/12
to
> stable pretty quick.
>
Yes, but I found that various values of output capacitance could cause
oscillations. I am not equipped to handle that. Please let me know if
you find a solution.
John
John Fields
Oct 11, 2012, 5:15:44 PM10/11/12
to
On Thu, 11 Oct 2012 15:13:18 -0500, John S <Sop...@invalid.org>
>> With C2 equal to a minimum of 100µF, it looks like the output gets
Anything > 100µF works fine here.
BTW, I changed the LTC1050 to an LTC2050:
Version 4
SHEET 1 880 680
WIRE -240 -128 -384 -128
WIRE 0 -128 -240 -128
WIRE 224 -128 0 -128
WIRE -240 -64 -240 -128
WIRE 0 32 0 -128
WIRE 224 64 224 -128
WIRE -240 80 -240 16
WIRE -32 80 -240 80
WIRE 160 112 112 112
WIRE -32 144 -80 144
WIRE 0 208 0 192
WIRE 224 240 224 160
WIRE 16 256 -80 256
WIRE 32 256 16 256
WIRE 128 256 112 256
WIRE -384 272 -384 -128
WIRE -240 272 -240 80
WIRE -80 304 -80 256
WIRE 48 336 16 336
WIRE 128 336 128 256
WIRE 128 336 112 336
WIRE -80 416 -240 416
SYMATTR InstName V1
SYMBOL pnp 160 160 M180
SYMATTR SpiceLine ""
SYMBOL Opamps\\LTC2050 0 112 R0
SYMATTR InstName U3
>> stable pretty quick.
>>
>
>Yes, but I found that various values of output capacitance could cause
>oscillations. I am not equipped to handle that. Please let me know if
>you find a solution.
---
>>
>
>Yes, but I found that various values of output capacitance could cause
>oscillations. I am not equipped to handle that. Please let me know if
>you find a solution.
Anything > 100µF works fine here.
BTW, I changed the LTC1050 to an LTC2050:
Version 4
SHEET 1 880 680
WIRE 0 -128 -240 -128
WIRE 224 -128 0 -128
WIRE -240 -64 -240 -128
WIRE 0 32 0 -128
WIRE 224 64 224 -128
WIRE -240 80 -240 16
WIRE -32 80 -240 80
WIRE 160 112 112 112
WIRE -32 144 -80 144
WIRE 0 208 0 192
WIRE 224 240 224 160
WIRE 304 240 224 240
WIRE 336 240 304 240
WIRE -80 256 -80 144
WIRE 336 240 304 240
WIRE 16 256 -80 256
WIRE 32 256 16 256
WIRE 128 256 112 256
WIRE 224 256 224 240
WIRE 224 256 128 256
WIRE -384 272 -384 -128
WIRE -240 272 -240 80
WIRE -80 304 -80 256
WIRE 224 304 224 256
WIRE 304 304 304 240
WIRE 16 336 16 256
WIRE 304 304 304 240
WIRE 48 336 16 336
WIRE 128 336 128 256
WIRE 128 336 112 336
WIRE -384 416 -384 352
WIRE -240 416 -240 336
WIRE -240 416 -384 416
WIRE -80 416 -80 384
WIRE -240 416 -240 336
WIRE -240 416 -384 416
WIRE -80 416 -240 416
WIRE 224 416 224 384
WIRE 224 416 -80 416
WIRE 304 416 304 368
WIRE 304 416 224 416
WIRE -384 464 -384 416
FLAG -384 464 0
FLAG 336 240 Vout
FLAG 0 208 0
WIRE 304 416 224 416
WIRE -384 464 -384 416
FLAG -384 464 0
FLAG 336 240 Vout
SYMBOL res 208 288 R0
SYMATTR InstName R1
SYMATTR Value 33
SYMATTR SpiceLine ""
SYMBOL voltage -384 256 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
WINDOW 3 24 96 Invisible 2
SYMATTR Value2 ""
SYMATTR SpiceLine ""
SYMATTR Value PULSE(0 6 .01 .001)
SYMATTR InstName R1
SYMATTR Value 33
SYMATTR SpiceLine ""
SYMBOL voltage -384 256 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
WINDOW 3 24 96 Invisible 2
SYMATTR Value2 ""
SYMATTR SpiceLine ""
SYMATTR InstName V1
SYMBOL pnp 160 160 M180
SYMATTR InstName Q1
SYMATTR Value 2N3906
SYMBOL res 16 240 M90
SYMATTR Value 2N3906
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 10k
SYMATTR SpiceLine ""
SYMBOL res -96 288 R0
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 10k
SYMATTR SpiceLine ""
WINDOW 0 -39 32 Left 2
WINDOW 3 -72 62 Left 2
SYMATTR InstName R3
SYMATTR Value 31250
SYMATTR SpiceLine ""
WINDOW 3 -72 62 Left 2
SYMATTR InstName R3
SYMATTR Value 31250
SYMATTR SpiceLine ""
SYMBOL References\\LT1634-2.5 -240 304 R0
WINDOW 3 12 -45 Left 2
WINDOW 0 15 -76 Left 2
SYMATTR InstName U2
SYMBOL res -256 -80 R0
WINDOW 3 12 -45 Left 2
WINDOW 0 15 -76 Left 2
SYMATTR InstName U2
SYMATTR InstName R4
SYMATTR Value 15K
SYMATTR SpiceLine ""
SYMBOL cap 112 320 R90
SYMATTR Value 15K
SYMATTR SpiceLine ""
WINDOW 0 65 33 VBottom 2
WINDOW 3 64 35 VTop 2
SYMATTR InstName C1
SYMATTR Value 1n
SYMATTR SpiceLine ""
SYMBOL cap 288 304 R0
SYMATTR InstName C2
SYMATTR Value 100µ
WINDOW 3 64 35 VTop 2
SYMATTR InstName C1
SYMATTR Value 1n
SYMATTR SpiceLine ""
SYMBOL cap 288 304 R0
SYMATTR InstName C2
SYMATTR SpiceLine ""
SYMBOL Opamps\\LTC2050 0 112 R0
SYMATTR InstName U3
Jamie
Oct 11, 2012, 11:04:41 PM10/11/12
to
>> stable pretty quick.
>>
>
> Yes, but I found that various values of output capacitance could cause
> oscillations. I am not equipped to handle that. Please let me know if
> you find a solution.
>
> John
>
This works.. Nice out put all the way down to 3.0 volts on the rail.
>>
>
> Yes, but I found that various values of output capacitance could cause
> oscillations. I am not equipped to handle that. Please let me know if
> you find a solution.
>
> John
>
Jamie
Version 4
SHEET 1 880 680
WIRE 224 -16 16 -16
WIRE 224 96 224 -16
WIRE 176 112 128 112
WIRE 16 160 16 -16
WIRE 128 160 128 112
WIRE 128 160 112 160
WIRE -16 240 -32 240
WIRE 64 240 64 224
WIRE 112 256 80 256
WIRE 224 256 224 192
WIRE 224 256 176 256
WIRE 304 256 224 256
WIRE 336 256 304 256
WIRE -384 272 -384 -16
WIRE -32 288 -32 240
WIRE 224 288 224 256
WIRE 304 288 304 256
WIRE 48 336 32 336
WIRE 80 336 48 336
WIRE -384 416 -384 352
WIRE -32 416 -32 384
WIRE -32 416 -384 416
WIRE 48 416 -32 416
WIRE 224 416 224 368
WIRE 224 416 48 416
WIRE 304 416 304 352
WIRE 304 416 224 416
WIRE -384 464 -384 416
FLAG -384 464 0
FLAG 128 32 0
WIRE -384 464 -384 416
FLAG -384 464 0
SYMBOL res 208 272 R0
SYMATTR InstName R1
SYMATTR Value 33
SYMATTR Value 33
SYMBOL voltage -384 256 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
WINDOW 3 24 96 Invisible 2
SYMATTR Value PULSE(3.5 6 .001 .01)
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
WINDOW 3 24 96 Invisible 2
SYMATTR InstName V1
SYMBOL References\\LT1634-2.5 144 256 R90
WINDOW 3 -43 -151 VTop 2
WINDOW 0 -27 0 VBottom 2
SYMATTR InstName U2
SYMBOL cap 288 288 R0
SYMATTR InstName C1
SYMATTR Value 10µ
SYMBOL pmos 176 192 M180
SYMATTR InstName M1
SYMATTR Value HAT1072H
SYMBOL res 112 16 R0
SYMATTR InstName R2
SYMATTR Value 1k
SYMBOL pnp 112 224 M270
SYMATTR InstName Q1
SYMATTR Value 2N2907
SYMBOL npn 32 288 M0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL res 80 224 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
WINDOW 3 32 56 VTop 2
SYMATTR Value 10k
SYMBOL res 32 320 R0
SYMATTR InstName R5
SYMATTR Value 56k
SYMBOL res 64 240 R0
SYMATTR InstName R4
SYMATTR Value 680
TEXT -376 440 Left 2 !.tran 0 .1 0 startup
John S
Oct 12, 2012, 11:55:09 AM10/12/12
to
On 10/11/2012 4:15 PM, John Fields wrote:
>>> Thanks, John.
>>>
>>> With C2 equal to a minimum of 100湩, it looks like the output gets
>>> Thanks, John.
>>>
>>> stable pretty quick.
>>>
>>
>> Yes, but I found that various values of output capacitance could cause
>> oscillations. I am not equipped to handle that. Please let me know if
>> you find a solution.
>
> ---
> Anything > 100湩 works fine here.
>>>
>>
>> Yes, but I found that various values of output capacitance could cause
>> oscillations. I am not equipped to handle that. Please let me know if
>> you find a solution.
>
> ---
>
> BTW, I changed the LTC1050 to an LTC2050:
Good move!
> BTW, I changed the LTC1050 to an LTC2050:
With a slight modification, it works with .01uF or greater:
Version 4
SHEET 1 880 680
WIRE -240 -128 -384 -128
WIRE 0 -128 -240 -128
WIRE 432 -80 432 -128
WIRE -240 -64 -240 -128
WIRE -80 -48 -96 -48
WIRE 272 -48 -16 -48
WIRE 0 32 0 -128
WIRE 432 64 432 0
WIRE -240 80 -240 16
WIRE -192 80 -240 80
WIRE -96 80 -96 -48
WIRE -96 80 -112 80
WIRE -32 80 -96 80
WIRE 144 112 112 112
WIRE 272 112 272 -48
WIRE 272 112 224 112
WIRE 368 112 272 112
WIRE -32 144 -80 144
WIRE 0 208 0 192
WIRE 432 240 432 160
WIRE 0 208 0 192
WIRE 512 240 432 240
WIRE 544 240 512 240
WIRE -80 256 -80 144
WIRE 16 256 -80 256
WIRE 32 256 16 256
WIRE 128 256 112 256
WIRE 432 256 432 240
WIRE 16 256 -80 256
WIRE 32 256 16 256
WIRE 128 256 112 256
WIRE 432 256 128 256
WIRE -384 272 -384 -128
WIRE -240 272 -240 80
WIRE -80 304 -80 256
WIRE 432 304 432 256
WIRE -240 272 -240 80
WIRE -80 304 -80 256
WIRE 512 304 512 240
WIRE 16 336 16 256
WIRE 48 336 16 336
WIRE 128 336 128 256
WIRE 128 336 112 336
WIRE -384 416 -384 352
WIRE -240 416 -240 336
WIRE -240 416 -384 416
WIRE -80 416 -80 384
WIRE -80 416 -240 416
WIRE 432 416 432 384
WIRE 48 336 16 336
WIRE 128 336 128 256
WIRE 128 336 112 336
WIRE -384 416 -384 352
WIRE -240 416 -240 336
WIRE -240 416 -384 416
WIRE -80 416 -80 384
WIRE -80 416 -240 416
WIRE 432 416 -80 416
WIRE 512 416 512 368
WIRE 512 416 432 416
WIRE -384 464 -384 416
FLAG -384 464 0
FLAG 544 240 Vout
FLAG -384 464 0
FLAG 0 208 0
SYMBOL res 416 288 R0
SYMATTR InstName R1
SYMATTR Value 33
SYMATTR Value 33
SYMBOL voltage -384 256 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
WINDOW 3 24 96 Invisible 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
WINDOW 3 24 96 Invisible 2
SYMATTR Value PULSE(0 6 .01 .001)
SYMATTR InstName V1
SYMBOL pnp 368 160 M180
SYMATTR InstName V1
SYMATTR InstName Q1
SYMATTR Value 2N3906
SYMBOL res 16 240 M90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 10k
SYMATTR Value 2N3906
SYMBOL res 16 240 M90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL res -96 288 R0
WINDOW 0 -39 32 Left 2
WINDOW 3 -72 62 Left 2
SYMATTR InstName R3
SYMATTR Value 31250
WINDOW 0 -39 32 Left 2
WINDOW 3 -72 62 Left 2
SYMATTR InstName R3
SYMATTR Value 31250
SYMBOL References\\LT1634-2.5 -240 304 R0
WINDOW 3 12 -45 Left 2
WINDOW 0 15 -76 Left 2
SYMATTR InstName U2
SYMBOL res -256 -80 R0
SYMATTR InstName R4
SYMATTR Value 15K
WINDOW 3 12 -45 Left 2
WINDOW 0 15 -76 Left 2
SYMATTR InstName U2
SYMBOL res -256 -80 R0
SYMATTR InstName R4
SYMATTR Value 15K
SYMBOL cap 112 320 R90
WINDOW 0 65 33 VBottom 2
WINDOW 3 64 35 VTop 2
SYMATTR InstName C1
SYMATTR Value 1n
SYMBOL cap 496 304 R0
WINDOW 0 65 33 VBottom 2
WINDOW 3 64 35 VTop 2
SYMATTR InstName C1
SYMATTR Value 1n
SYMATTR InstName C2
SYMATTR Value .01u
SYMBOL Opamps\\LTC2050 0 112 R0
SYMATTR InstName U3
SYMBOL res 416 -96 R0
SYMATTR InstName U3
SYMATTR InstName R5
SYMATTR Value 10
SYMBOL res -208 64 M90
SYMATTR Value 10
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R6
WINDOW 3 32 56 VTop 2
SYMATTR Value 10k
SYMBOL cap -16 -64 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C3
SYMATTR Value 22p
SYMBOL res 128 96 M90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R7
WINDOW 3 32 56 VTop 2
SYMATTR Value 1000
TEXT -376 440 Left 2 !.tran .5
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