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Multiple regulated voltages

Started by Piotr Wyderski June 13, 2019
I need +/-10V (about 1A), +/-2.5V (about 100mA) and 5V (about 60mA).
I was shocked that it is virtually impossible to find a negative voltage
LDO capable of hundreds of milliamps and reasonably cheap. It seems
that producing all these rails with a bunch of opamp-boosted emitter 
followers will be cheaper than a single adjustable negative LDO.
I already have a decent 2.5V reference (LTC6655) in the project so why
exactly should I avoid the temptation of making this PSU out of discrete 
elements? Noise properties should be comparable to that of an LDO and
I can shape thermal/max voltage issues with a proper transistor.

	Best regards, Piotr
Piotr Wyderski wrote...
> > I need +/-10V (about 1A), +/-2.5V (about 100mA) and 5V > (about 60mA). I was shocked that it is virtually > impossible to find a negative voltage LDO capable of > hundreds of milliamps and reasonably cheap.
I'm surprised you want to waste 1.8 watts on 5V and 2.5V linear regulators. It's easy to make negative buck converters from positive boost converters. -- Thanks, - Win
Winfield Hill wrote:

> I'm surprised you want to waste 1.8 watts on 5V and > 2.5V linear regulators. It's easy to make negative > buck converters from positive boost converters.
The fans consume 65W, so there is no real reason to care about 2 additional watts. And the rails will be quiet, which is a nice feature in the vincinity of a 24-bit ADC. Best regards, Piotr
On Thursday, June 13, 2019 at 2:14:08 PM UTC-4, Piotr Wyderski wrote:
> I need +/-10V (about 1A), +/-2.5V (about 100mA) and 5V (about 60mA). > I was shocked that it is virtually impossible to find a negative voltage > LDO capable of hundreds of milliamps and reasonably cheap. It seems > that producing all these rails with a bunch of opamp-boosted emitter > followers will be cheaper than a single adjustable negative LDO. > I already have a decent 2.5V reference (LTC6655) in the project so why > exactly should I avoid the temptation of making this PSU out of discrete > elements? Noise properties should be comparable to that of an LDO and > I can shape thermal/max voltage issues with a proper transistor. > > Best regards, Piotr
What do you have for input voltage/current? I guess the LM337 doesn't count as LDO. Two wall warts for the +/- 10V? There are also a number of DC-DC converter modules. But 1 amp may cost too much. George H.
Winfield Hill <winfieldhill@yahoo.com> wrote in 
news:qdu5ft0260h@drn.newsguy.com:

> Piotr Wyderski wrote... >> >> I need +/-10V (about 1A), +/-2.5V (about 100mA) and 5V >> (about 60mA). I was shocked that it is virtually >> impossible to find a negative voltage LDO capable of >> hundreds of milliamps and reasonably cheap. > > I'm surprised you want to waste 1.8 watts on 5V and > 2.5V linear regulators. It's easy to make negative > buck converters from positive boost converters. > >
Our oem lvsmps with multiple outputs were practically the same as the single output jobs. Usually a bit smaller than a brick. We made about 400V and then downconvert for the actual output voltages. Running the 400V rail clean made the supply LV setpoints easier to manage and keep clean.
George Herold wrote...
> >On Thursday, June 13, 2019 at 2:14:08 PM UTC-4, Piotr Wyderski wrote: >> I need +/-10V (about 1A), +/-2.5V (about 100mA) and 5V (about 60mA). >> I was shocked that it is virtually impossible to find a negative voltage >> LDO capable of hundreds of milliamps and reasonably cheap. > > I guess the LM337 doesn't count as LDO.
Why would one need an LDO to go from -10V to -2.5V? -- Thanks, - Win
On 13 Jun 2019 12:28:30 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:

>George Herold wrote... >> >>On Thursday, June 13, 2019 at 2:14:08 PM UTC-4, Piotr Wyderski wrote: >>> I need +/-10V (about 1A), +/-2.5V (about 100mA) and 5V (about 60mA). >>> I was shocked that it is virtually impossible to find a negative voltage >>> LDO capable of hundreds of milliamps and reasonably cheap. >> >> I guess the LM337 doesn't count as LDO. > > Why would one need an LDO to go from -10V to -2.5V?
Some people have taken to calling any linear regulator an LDO. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Thursday, June 13, 2019 at 3:28:53 PM UTC-4, Winfield Hill wrote:
> George Herold wrote... > > > >On Thursday, June 13, 2019 at 2:14:08 PM UTC-4, Piotr Wyderski wrote: > >> I need +/-10V (about 1A), +/-2.5V (about 100mA) and 5V (about 60mA). > >> I was shocked that it is virtually impossible to find a negative voltage > >> LDO capable of hundreds of milliamps and reasonably cheap. > > > > I guess the LM337 doesn't count as LDO. > > Why would one need an LDO to go from -10V to -2.5V? >
Grin you wouldn't. I assumed the LDO was for the -10 V. George h.
> > -- > Thanks, > - Win
On a sunny day (Thu, 13 Jun 2019 20:14:06 +0200) it happened Piotr Wyderski
<peter.pan@neverland.mil> wrote in <qdu3pb$vnn$1@node2.news.atman.pl>:

>I need +/-10V (about 1A), +/-2.5V (about 100mA) and 5V (about 60mA). >I was shocked that it is virtually impossible to find a negative voltage >LDO capable of hundreds of milliamps and reasonably cheap. It seems >that producing all these rails with a bunch of opamp-boosted emitter >followers will be cheaper than a single adjustable negative LDO. >I already have a decent 2.5V reference (LTC6655) in the project so why >exactly should I avoid the temptation of making this PSU out of discrete >elements? Noise properties should be comparable to that of an LDO and >I can shape thermal/max voltage issues with a proper transistor. > > Best regards, Piotr
As long as you do not specify tolerances and ripple, you may as well use a tapped transformer a few diodes and capacitors and some oscillator. That is how PC power supplies work.
On Thursday, June 13, 2019 at 3:40:36 PM UTC-4, John Larkin wrote:
> On 13 Jun 2019 12:28:30 -0700, Winfield Hill <winfieldhill@yahoo.com> > wrote: > > >George Herold wrote... > >> > >>On Thursday, June 13, 2019 at 2:14:08 PM UTC-4, Piotr Wyderski wrote: > >>> I need +/-10V (about 1A), +/-2.5V (about 100mA) and 5V (about 60mA). > >>> I was shocked that it is virtually impossible to find a negative voltage > >>> LDO capable of hundreds of milliamps and reasonably cheap. > >> > >> I guess the LM337 doesn't count as LDO. > > > > Why would one need an LDO to go from -10V to -2.5V? > > Some people have taken to calling any linear regulator an LDO.
Right, I have no idea what an LDO is or isn't. I use the LT3080, called an LDO, but typical app has a drop out of 1.2 V. George h.
> > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com