Re: [time-nuts] ULN regulator with more current capability than LT3042?

[ed breya]

Before adding complexity of parallel devices or external passing, why 
not just try the old parallel-resistor trick? If the load takes a 
certain minimum current under all conditions, provide less than that via 
a resistor from the raw source to the regulated output, likewise under 
all conditions. The main regulator will still do its thing, but not have 
to supply all the current. You're just looking to get a little more 
margin between the spec current and actual load. The short-circuit 
current would be increased too, so take that into account.


Now some will say, "what about the ripple voltage from the raw supply 
causing ripple current going right to the output?" Depending on the 
regulator's characteristics, I think it should be able to handle it just 
fine - it's easy enough to hook it up and see how it works.


It would be good have OVP on the output regardless of the regulation 
scheme to protect the load if it's sensitive to OV. Obviously, the 
parallel resistor one could allow the voltage to go high if some load is 
lost, but the same can happen with a regulator failure too.


Ed

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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[John Miles]

> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of John
> Ackermann N8UR
>
> Reviving the conversation about superb voltage regulators, I am looking
> for one to run the analog and PLL bits of a high performance frequency
> synthesizer chip.
> 
> The current drain looks to be about 160-180 mA at 1.8 V, which is
> uncomfortably close to the limit for the LT3042 (200 mA).  The
> manufacturer's evaluation board uses a MAX8869, which appears to be
> nowhere in the LT3042's league, but will source 1 A.
> 
> Any recommendations for a 1.8 V regulator a little beefier than the
> LT3042, but with similar noise performance?

These days, the best RF synthesizer and clock generator chips include dedicated 
low-noise LDOs inside the package.  It's rarely worthwhile to use a quieter 
regulator than the manufacturer recommends, or one that's quieter than whatever 
is on their own demo board. 

One very nifty example is the LMK61E2, which I X-rayed a while back:
http://www.ke5fx.com/LMK61E2_30kVp_20s.png

The overall package is only about 1 cm square.  The synthesizer has its own 
die, while the input regulators and (presumably) their bypass caps are mounted 
directly above the Vdd input pad.  According to TI, the PSRR of the internal 
LDO that runs the analog section is better than 70 dB at offsets below 1 MHz.  
So you could even power it directly from a switcher, assuming you keep a leash 
on its harmonics. 

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[Gerhard Hoffmann]

Am 20.03.2018 um 10:09 schrieb Attila Kinali:

Hoi Gerhard,

On Sun, 18 Mar 2018 21:41:28 +0100
Gerhard Hoffmann  wrote:


Use the LT3042 with an external power transistor, such as D44VH10G:

<
https://www.flickr.com/photos/137684711@N07/29197476530/in/album-72157662535945536/
  >

Performance is about the same as the LT3042 alone. That is exactly the
circuit from the data sheet

Have you measured it's dynamic performance?
I did some spice simulations some time ago and noticed that there are
some load conditions where this circuit is very close to oscillation
(ie load changes lead to heavy ringing)of course, this is under
the assumption that the spice model of the LT3042 is accurate in that
regard.

No, I didn't. My oscillators are quite boring loads for a regulator.

regards, Gerhard

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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[Attila Kinali]

Hoi Gerhard,

On Sun, 18 Mar 2018 21:41:28 +0100
Gerhard Hoffmann  wrote:

> Use the LT3042 with an external power transistor, such as D44VH10G:
> 
> < 
> https://www.flickr.com/photos/137684711@N07/29197476530/in/album-72157662535945536/
>  
>  >
> 
> Performance is about the same as the LT3042 alone. That is exactly the 
> circuit from the data sheet

Have you measured it's dynamic performance?
I did some spice simulations some time ago and noticed that there are
some load conditions where this circuit is very close to oscillation
(ie load changes lead to heavy ringing)of course, this is under
the assumption that the spice model of the LT3042 is accurate in that
regard.

Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[Bruce Griffiths]

I have a quad LT3042 board somewhere.
I should get around to measuring its output noise.

Bruce 
> On 20 March 2018 at 03:11 John Ackermann N8UR  wrote:
> 
> 
> Thanks, all.  I think I'll end up using the 3042 with pass transistor, 
> partly for reasons of cost.  I have no idea whether paralleling two 
> 3042s would result in lower noise from the device, and there are already 
> three or four fairly pricey chips on the board.
> 
> I appreciate all the info!
> 
> John
> 
> 
> On 03/18/2018 06:43 PM, Charles Steinmetz wrote:
> > Tom wrote:
> > 
> >> Run two in parallel for twice the current and less noise?
> > 
> > This is actually a better solution than using an LT3045, for two 
> > reasons.  First, as Tom noted, by paralleling two devices, the noise is 
> > reduced by sqrt 2 = ~1.4:
> > 
> > "Designed as a precision current reference followed by a high 
> > performance voltage buffer, the LT3042 is easily paralleled to increase 
> > output current, spread heat on the PCB and further reduce noise -- 
> > output noise decreases by the square-root of the number of devices in 
> > parallel."  [LT Journal of Analog Innovation, v25 n1 Apr 2015]. 
> > 
> > 
> > Second, it reduces the dissipation of each regulator, so they run 
> > cooler.  And as LT says, it allows spreading the heat on the board (but 
> > it is not advisable to put them too far apart).
> > 
> > The primary disadvantage is that two 3042s cost about half again more 
> > than one 3045.  Also, board space may be a factor in some applications.
> > 
> > So, unless you are extremely tight on board space or the ~1.5x cost 
> > increase is prohibitive, two 3042s in parallel are a better solution 
> > than one 3045 if you are seeking the lowest noise possible.
> > 
> > Best regards,
> > 
> > Charles
> > 
> > 
> > ___
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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[Bruce Griffiths]

The details are on the LT3042 datasheet.

A small series ballast resistor is used in series with each output and the Iref 
terminals are connected in parallel so only the offset of the unity gain output 
buffer is of significance.

Bruce

> 
> On 20 March 2018 at 02:23 Peter Vince  wrote:
> 
> Please forgive this naive question, but I am concerned about the idea of
> simply running two regulators in parallel. Just like you don't put two
> batteries in parallel, how do you ensure accurate load balancing between
> the two? I would worry that one of them, with a fractionally higher
> voltage, would be driven into saturation, thus ruining any noise
> isolation. I must be missing something here?
> 
> Peter
> 
> On 18 March 2018 at 22:43, Charles Steinmetz  
> wrote:
> 
> > > 
> > Tom wrote:
> > 
> > Run two in parallel for twice the current and less noise?
> > >
> > 
> > This is actually a better solution than using an LT3045, for two 
> > reasons.
> > First, as Tom noted, by paralleling two devices, the noise is 
> > reduced by
> > sqrt 2 = ~1.4:
> > 
> > "Designed as a precision current reference followed by a high 
> > performance
> > voltage buffer, the LT3042 is easily paralleled to increase output 
> > current,
> > spread heat on the PCB and further reduce noise -- output noise 
> > decreases
> > by the square-root of the number of devices in parallel." [LT 
> > Journal of
> > Analog Innovation, v25 n1 Apr 2015]. 
> > 
> > 
> > Second, it reduces the dissipation of each regulator, so they run 
> > cooler.
> > And as LT says, it allows spreading the heat on the board (but it 
> > is not
> > advisable to put them too far apart).
> > 
> > The primary disadvantage is that two 3042s cost about half again 
> > more than
> > one 3045. Also, board space may be a factor in some applications.
> > 
> > So, unless you are extremely tight on board space or the ~1.5x cost
> > increase is prohibitive, two 3042s in parallel are a better 
> > solution than
> > one 3045 if you are seeking the lowest noise possible.
> > 
> > Best regards,
> > 
> > Charles
> > 
> > ___
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> > ailman/listinfo/time-nuts
> > and follow the instructions there.
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> > 
> > > 
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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[John Ackermann N8UR]

Thanks, all.  I think I'll end up using the 3042 with pass transistor, 
partly for reasons of cost.  I have no idea whether paralleling two 
3042s would result in lower noise from the device, and there are already 
three or four fairly pricey chips on the board.


I appreciate all the info!

John


On 03/18/2018 06:43 PM, Charles Steinmetz wrote:

Tom wrote:


Run two in parallel for twice the current and less noise?


This is actually a better solution than using an LT3045, for two 
reasons.  First, as Tom noted, by paralleling two devices, the noise is 
reduced by sqrt 2 = ~1.4:


"Designed as a precision current reference followed by a high 
performance voltage buffer, the LT3042 is easily paralleled to increase 
output current, spread heat on the PCB and further reduce noise -- 
output noise decreases by the square-root of the number of devices in 
parallel."  [LT Journal of Analog Innovation, v25 n1 Apr 2015]. 



Second, it reduces the dissipation of each regulator, so they run 
cooler.  And as LT says, it allows spreading the heat on the board (but 
it is not advisable to put them too far apart).


The primary disadvantage is that two 3042s cost about half again more 
than one 3045.  Also, board space may be a factor in some applications.


So, unless you are extremely tight on board space or the ~1.5x cost 
increase is prohibitive, two 3042s in parallel are a better solution 
than one 3045 if you are seeking the lowest noise possible.


Best regards,

Charles


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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[Peter Vince]

Please forgive this naive question, but I am concerned about the idea of
simply running two regulators in parallel.  Just like you don't put two
batteries in parallel, how do you ensure accurate load balancing between
the two?  I would worry that one of them, with a fractionally higher
voltage, would be driven into saturation, thus ruining any noise
isolation.  I must be missing something here?

 Peter


On 18 March 2018 at 22:43, Charles Steinmetz  wrote:

> Tom wrote:
>
> Run two in parallel for twice the current and less noise?
>>
>
> This is actually a better solution than using an LT3045, for two reasons.
> First, as Tom noted, by paralleling two devices, the noise is reduced by
> sqrt 2 = ~1.4:
>
> "Designed as a precision current reference followed by a high performance
> voltage buffer, the LT3042 is easily paralleled to increase output current,
> spread heat on the PCB and further reduce noise -- output noise decreases
> by the square-root of the number of devices in parallel."  [LT Journal of
> Analog Innovation, v25 n1 Apr 2015]. 
>
> Second, it reduces the dissipation of each regulator, so they run cooler.
> And as LT says, it allows spreading the heat on the board (but it is not
> advisable to put them too far apart).
>
> The primary disadvantage is that two 3042s cost about half again more than
> one 3045.  Also, board space may be a factor in some applications.
>
> So, unless you are extremely tight on board space or the ~1.5x cost
> increase is prohibitive, two 3042s in parallel are a better solution than
> one 3045 if you are seeking the lowest noise possible.
>
> Best regards,
>
> Charles
>
>
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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[Charles Steinmetz]

Tom wrote:


Run two in parallel for twice the current and less noise?


This is actually a better solution than using an LT3045, for two 
reasons.  First, as Tom noted, by paralleling two devices, the noise is 
reduced by sqrt 2 = ~1.4:


"Designed as a precision current reference followed by a high 
performance voltage buffer, the LT3042 is easily paralleled to increase 
output current, spread heat on the PCB and further reduce noise -- 
output noise decreases by the square-root of the number of devices in 
parallel."  [LT Journal of Analog Innovation, v25 n1 Apr 2015]. 



Second, it reduces the dissipation of each regulator, so they run 
cooler.  And as LT says, it allows spreading the heat on the board (but 
it is not advisable to put them too far apart).


The primary disadvantage is that two 3042s cost about half again more 
than one 3045.  Also, board space may be a factor in some applications.


So, unless you are extremely tight on board space or the ~1.5x cost 
increase is prohibitive, two 3042s in parallel are a better solution 
than one 3045 if you are seeking the lowest noise possible.


Best regards,

Charles


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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[Bob kb8tq]

Hi

Getting the heat off of the regulator package may have other benefits ( like 
improved
stability).  A lot depends on just where the heat goes in each case …..

Bob

> On Mar 18, 2018, at 4:41 PM, Gerhard Hoffmann  wrote:
> 
> 
> 
> Am 18.03.2018 um 21:13 schrieb John Ackermann N8UR:
>> Reviving the conversation about superb voltage regulators, I am looking for 
>> one to run the analog and PLL bits of a high performance frequency 
>> synthesizer chip.
>> 
>> The current drain looks to be about 160-180 mA at 1.8 V, which is 
>> uncomfortably close to the limit for the LT3042 (200 mA).  The 
>> manufacturer's evaluation board uses a MAX8869, which appears to be nowhere 
>> in the LT3042's league, but will source 1 A.
>> 
>> Any recommendations for a 1.8 V regulator a little beefier than the LT3042, 
>> but with similar noise performance?
>> 
> 
> 
> Use the LT3042 with an external power transistor, such as D44VH10G:
> 
> < 
> https://www.flickr.com/photos/137684711@N07/29197476530/in/album-72157662535945536/
>  >
> 
> Performance is about the same as the LT3042 alone. That is exactly the 
> circuit from the data sheet.
> 
> < 
> https://www.flickr.com/photos/137684711@N07/29452163806/in/album-72157662535945536/
>  >
> 
> The layout for Altium Designer is available.
> 
> The LT3045 is not so much bigger that it makes a real progress. The currents 
> are valid only
> for tiny voltage drops anyway.
> 
> regards,
> Gerhard
> 
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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[Gerhard Hoffmann]

Am 18.03.2018 um 21:13 schrieb John Ackermann N8UR:
Reviving the conversation about superb voltage regulators, I am 
looking for one to run the analog and PLL bits of a high performance 
frequency synthesizer chip.


The current drain looks to be about 160-180 mA at 1.8 V, which is 
uncomfortably close to the limit for the LT3042 (200 mA).  The 
manufacturer's evaluation board uses a MAX8869, which appears to be 
nowhere in the LT3042's league, but will source 1 A.


Any recommendations for a 1.8 V regulator a little beefier than the 
LT3042, but with similar noise performance?





Use the LT3042 with an external power transistor, such as D44VH10G:

< 
https://www.flickr.com/photos/137684711@N07/29197476530/in/album-72157662535945536/ 
>


Performance is about the same as the LT3042 alone. That is exactly the 
circuit from the data sheet.


< 
https://www.flickr.com/photos/137684711@N07/29452163806/in/album-72157662535945536/ 
>


The layout for Altium Designer is available.

The LT3045 is not so much bigger that it makes a real progress. The 
currents are valid only

for tiny voltage drops anyway.

regards,
Gerhard

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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[John Ackermann N8UR]

Thanks, Bruce!!!

On 03/18/2018 04:19 PM, Bruce Griffiths wrote:

Use an LT3045, its the 0.5A version of the LT3042.

Bruce

On 19 March 2018 at 09:13 John Ackermann N8UR  wrote:


Reviving the conversation about superb voltage regulators, I am looking
for one to run the analog and PLL bits of a high performance frequency
synthesizer chip.

The current drain looks to be about 160-180 mA at 1.8 V, which is
uncomfortably close to the limit for the LT3042 (200 mA).  The
manufacturer's evaluation board uses a MAX8869, which appears to be
nowhere in the LT3042's league, but will source 1 A.

Any recommendations for a 1.8 V regulator a little beefier than the
LT3042, but with similar noise performance?

Thanks!
John
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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[Tom Miller]

- Original Message - 
From: "John Ackermann N8UR" 
To: "Discussion of precise time and frequency measurement" 


Sent: Sunday, March 18, 2018 4:13 PM
Subject: [time-nuts] ULN regulator with more current capability than LT3042?


Reviving the conversation about superb voltage regulators, I am looking 
for one to run the analog and PLL bits of a high performance frequency 
synthesizer chip.


The current drain looks to be about 160-180 mA at 1.8 V, which is 
uncomfortably close to the limit for the LT3042 (200 mA).  The 
manufacturer's evaluation board uses a MAX8869, which appears to be 
nowhere in the LT3042's league, but will source 1 A.


Any recommendations for a 1.8 V regulator a little beefier than the 
LT3042, but with similar noise performance?


Thanks!
John
___


Run two in parallel for twice the current and less noise?

Regards 


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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[Bruce Griffiths]

Use an LT3045, its the 0.5A version of the LT3042.

Bruce
> On 19 March 2018 at 09:13 John Ackermann N8UR  wrote:
> 
> 
> Reviving the conversation about superb voltage regulators, I am looking 
> for one to run the analog and PLL bits of a high performance frequency 
> synthesizer chip.
> 
> The current drain looks to be about 160-180 mA at 1.8 V, which is 
> uncomfortably close to the limit for the LT3042 (200 mA).  The 
> manufacturer's evaluation board uses a MAX8869, which appears to be 
> nowhere in the LT3042's league, but will source 1 A.
> 
> Any recommendations for a 1.8 V regulator a little beefier than the 
> LT3042, but with similar noise performance?
> 
> Thanks!
> John
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[time-nuts] ULN regulator with more current capability than LT3042?

[John Ackermann N8UR]

Reviving the conversation about superb voltage regulators, I am looking 
for one to run the analog and PLL bits of a high performance frequency 
synthesizer chip.


The current drain looks to be about 160-180 mA at 1.8 V, which is 
uncomfortably close to the limit for the LT3042 (200 mA).  The 
manufacturer's evaluation board uses a MAX8869, which appears to be 
nowhere in the LT3042's league, but will source 1 A.


Any recommendations for a 1.8 V regulator a little beefier than the 
LT3042, but with similar noise performance?


Thanks!
John
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