My TI rep was being difficult, so I just bought an eval board from
Digikey for $100.
It makes a nice 4.993 volt output, but it's wicked noisy.
https://www.dropbox.com/scl/fo/8fybyu5l3w4tdgt1y0386/AFunYi9K15UgNpkQzEbYaVA?rlkey=j261b4ca5kc966vq2y03fw0md&dl=0
53% efficient into that 0.25 watt load.
john larkin <jl@glen--canyon.com> wrote:
My TI rep was being difficult, so I just bought an eval board from
Digikey for $100.
It makes a nice 4.993 volt output, but it's wicked noisy.
https://www.dropbox.com/scl/fo/8fybyu5l3w4tdgt1y0386/AFunYi9K15UgNpkQzEbYaVA?rlkey=j261b4ca5kc966vq2y03fw0md&dl=0
53% efficient into that 0.25 watt load.
Yikes, what a piece of junk. Small maybe, but lots of parts needed for >cleanup.
What does it do to the input rail?
Cheers
Phil Hobbs
On Wed, 9 Apr 2025 23:45:23 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@glen--canyon.com> wrote:
My TI rep was being difficult, so I just bought an eval board from
Digikey for $100.
It makes a nice 4.993 volt output, but it's wicked noisy.
https://www.dropbox.com/scl/fo/8fybyu5l3w4tdgt1y0386/AFunYi9K15UgNpkQzEbYaVA?rlkey=j261b4ca5kc966vq2y03fw0md&dl=0
53% efficient into that 0.25 watt load.
Yikes, what a piece of junk. Small maybe, but lots of parts needed for
cleanup.
What does it do to the input rail?
Cheers
Phil Hobbs
I didn't scope the input rail. I expect it has lots of noise and DC
load in bursts.
The architecture seems to be a simple forward converter with lots of
step-up, and regulates bang-bang in inefficient bursts. I expect that
if I reduced the input voltage, it woud get more efficient as the
bursts approach 100% duty cycle and it starts to lose regulation.
I took the rig down. It won't work in my application, as a high side
gate drive supply in a GaN half-bridge. Way too noisy.
I love the idea of a tiny cheap dc/dc converter on a chip, but not
this one.
$100 for this eval board is silly too. It comes with a generic
application brochure that says "go to the web site"
I now have, in theory, three TI support engineers, whose universal
support is "go to the forums."
I remember in the olden days when our TI guys would show up with a
briefcase full of data books and unexpected new samples.
My TI rep was being difficult, so I just bought an eval board from
Digikey for $100.
It makes a nice 4.993 volt output, but it's wicked noisy.
https://www.dropbox.com/scl/fo/8fybyu5l3w4tdgt1y0386/AFunYi9K15UgNpkQzEbYaVA?rlkey=j261b4ca5kc966vq2y03fw0md&dl=0
53% efficient into that 0.25 watt load.
john larkin <jl@glen--canyon.com> wrote:
My TI rep was being difficult, so I just bought an eval board from
Digikey for $100.
It makes a nice 4.993 volt output, but it's wicked noisy.
https://www.dropbox.com/scl/fo/8fybyu5l3w4tdgt1y0386/AFunYi9K15UgNpkQzEbYaVA?rlkey=j261b4ca5kc966vq2y03fw0md&dl=0
53% efficient into that 0.25 watt load.
I think this high frequency noise should be easy to filter by some CLC >Filter.
On 10 Apr 2025 08:48:48 GMT, Uwe Bonnes <bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
...
I think this high frequency noise should be easy to filter by some CLC >>Filter.
Not really. I need it to be close to the load, and that load is super
noise sensitive. I didn't check, but there is no doubt some
considerable and nasty emitted mag fields too.
In addition to all the high frequency crud, there's the basic burst
and its side effects in the hundreds of KHz range, would would take
giant parts to filter.
There are interesting parts around now that include their own power isolation. Some are capacitive, not inductive, so may be better.
john larkin <jl@glen--canyon.com> wrote:
On 10 Apr 2025 08:48:48 GMT, Uwe Bonnes
<bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
...
I think this high frequency noise should be easy to filter by some CLC >>>Filter.
Not really. I need it to be close to the load, and that load is super
noise sensitive. I didn't check, but there is no doubt some
considerable and nasty emitted mag fields too.
Of course, the vincinity of any isolated DCDC is super noisy. If
nothing else helps, think about battery power.
In addition to all the high frequency crud, there's the basic burst
and its side effects in the hundreds of KHz range, would would take
giant parts to filter.
Look at LDOs with good PSRR at high frequency. From the datasheet, the >TPS7A20XX is still in the 40 db range at 1 MHZ. The LT1963 may be
better, but is much more expensive, the TPS7A20 is rather cheap and >available.
There are interesting parts around now that include their own power
isolation. Some are capacitive, not inductive, so may be better.
What part do you expect to have capacitive power transport? Capacitive >signaling is however common.
B.t.w, looking at a ISOW7841, I also see frequency in the 50 Mhz
range.
Wuerth WPME-CDIP Capacitive Digital Isolator Powered talks about 13 MHz
On 10 Apr 2025 15:56:04 GMT, Uwe Bonnes <bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
john larkin <jl@glen--canyon.com> wrote:
On 10 Apr 2025 08:48:48 GMT, Uwe Bonnes
<bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
...
I think this high frequency noise should be easy to filter by some CLC >>>> Filter.
Not really. I need it to be close to the load, and that load is super
noise sensitive. I didn't check, but there is no doubt some
considerable and nasty emitted mag fields too.
Of course, the vincinity of any isolated DCDC is super noisy. If
nothing else helps, think about battery power.
I'm considering a bootstrap circuit to handle the switching power
assisted by a photovoltaic source for steady-state. I can bootstrap
off my own output pulse.
In addition to all the high frequency crud, there's the basic burst
and its side effects in the hundreds of KHz range, would would take
giant parts to filter.
Look at LDOs with good PSRR at high frequency. From the datasheet, the
TPS7A20XX is still in the 40 db range at 1 MHZ. The LT1963 may be
better, but is much more expensive, the TPS7A20 is rather cheap and
available.
There are interesting parts around now that include their own power
isolation. Some are capacitive, not inductive, so may be better.
What part do you expect to have capacitive power transport? Capacitive
signaling is however common.
B.t.w, looking at a ISOW7841, I also see frequency in the 50 Mhz
range.
I suspect it uses similar power isolation as the UCCpart.
Wuerth WPME-CDIP Capacitive Digital Isolator Powered talks about 13 MHz
ADE9113 has power isolation too, and it also sounds magnetic. I
thought I saw a capacitive power isolator somewhere.
On 2025-04-10 12:11, john larkin wrote:
On 10 Apr 2025 15:56:04 GMT, Uwe BonnesThat sounds like fun--if you do that, please let us know how it works!
<bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
john larkin <jl@glen--canyon.com> wrote:
On 10 Apr 2025 08:48:48 GMT, Uwe Bonnes
<bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
...
I think this high frequency noise should be easy to filter by some CLC >>>>> Filter.
Not really. I need it to be close to the load, and that load is super
noise sensitive. I didn't check, but there is no doubt some
considerable and nasty emitted mag fields too.
Of course, the vincinity of any isolated DCDC is super noisy. If
nothing else helps, think about battery power.
I'm considering a bootstrap circuit to handle the switching power
assisted by a photovoltaic source for steady-state. I can bootstrap
off my own output pulse.
In addition to all the high frequency crud, there's the basic burst
and its side effects in the hundreds of KHz range, would would take
giant parts to filter.
Look at LDOs with good PSRR at high frequency. From the datasheet, the
TPS7A20XX is still in the 40 db range at 1 MHZ. The LT1963 may be
better, but is much more expensive, the TPS7A20 is rather cheap and
available.
There are interesting parts around now that include their own power
isolation. Some are capacitive, not inductive, so may be better.
What part do you expect to have capacitive power transport? Capacitive
signaling is however common.
B.t.w, looking at a ISOW7841, I also see frequency in the 50 Mhz
range.
I suspect it uses similar power isolation as the UCCpart.
Wuerth WPME-CDIP Capacitive Digital Isolator Powered talks about 13 MHz
ADE9113 has power isolation too, and it also sounds magnetic. I
thought I saw a capacitive power isolator somewhere.
Jim Williams used to write about piezoelectric transformers, back in his >CC-fluorescent backlight days. (May they never return--fluorescent
lights suck eggs.)
The PVs are affordable and of course marvelously quiet, but they max
out typically below 100 uA. That gets tricky.
On 11/04/2025 3:56 am, john larkin wrote:
The PVs are affordable and of course marvelously quiet, but they max
out typically below 100 uA. That gets tricky.
You can get more powerful ones for "power over fibre" with a laser at
the other end. I vaguely remember there being an example in AOE3.
On Thu, 10 Apr 2025 12:36:34 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2025-04-10 12:11, john larkin wrote:
On 10 Apr 2025 15:56:04 GMT, Uwe BonnesThat sounds like fun--if you do that, please let us know how it works!
<bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
john larkin <jl@glen--canyon.com> wrote:
On 10 Apr 2025 08:48:48 GMT, Uwe Bonnes
<bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
...
I think this high frequency noise should be easy to filter by some CLC >>>>>> Filter.
Not really. I need it to be close to the load, and that load is super >>>>> noise sensitive. I didn't check, but there is no doubt some
considerable and nasty emitted mag fields too.
Of course, the vincinity of any isolated DCDC is super noisy. If
nothing else helps, think about battery power.
I'm considering a bootstrap circuit to handle the switching power
assisted by a photovoltaic source for steady-state. I can bootstrap
off my own output pulse.
The PVs are affordable and of course marvelously quiet, but they max
out typically below 100 uA. That gets tricky.
I could consider a tiny supercap, assuming that my users won't try to
make weeks-long pulses.
In addition to all the high frequency crud, there's the basic burst
and its side effects in the hundreds of KHz range, would would take
giant parts to filter.
Look at LDOs with good PSRR at high frequency. From the datasheet, the >>>> TPS7A20XX is still in the 40 db range at 1 MHZ. The LT1963 may be
better, but is much more expensive, the TPS7A20 is rather cheap and
available.
There are interesting parts around now that include their own power
isolation. Some are capacitive, not inductive, so may be better.
What part do you expect to have capacitive power transport? Capacitive >>>> signaling is however common.
B.t.w, looking at a ISOW7841, I also see frequency in the 50 Mhz
range.
I suspect it uses similar power isolation as the UCCpart.
ADE9113 has power isolation too, and it also sounds magnetic. I
Wuerth WPME-CDIP Capacitive Digital Isolator Powered talks about 13 MHz >>>
thought I saw a capacitive power isolator somewhere.
Jim Williams used to write about piezoelectric transformers, back in his
CC-fluorescent backlight days. (May they never return--fluorescent
lights suck eggs.)
I always thought the piezo transformer was cute. The real HV isolator
is a motor and a generator and a fiberglass shaft, all surface-mount
of course.
I threw out a bunch of incandescent bulbs and wish I'd kept a few. I
don't miss CFs at all.
On Fri, 11 Apr 2025 23:31:24 +1000, Chris Jones
<lugnut808@spam.yahoo.com> wrote:
On 11/04/2025 3:56 am, john larkin wrote:
The PVs are affordable and of course marvelously quiet, but they max
out typically below 100 uA. That gets tricky.
You can get more powerful ones for "power over fibre" with a laser at
the other end. I vaguely remember there being an example in AOE3.
I would love such a power optocoupler, if it were a reasonable size
and price.
There must be a market for a really quiet isolated dc/dc converter.
Maybe a sine wave thing.
On 12/04/2025 1:12 am, john larkin wrote:
On Fri, 11 Apr 2025 23:31:24 +1000, Chris Jones
<lugnut808@spam.yahoo.com> wrote:
On 11/04/2025 3:56 am, john larkin wrote:
The PVs are affordable and of course marvelously quiet, but they max
out typically below 100 uA. That gets tricky.
You can get more powerful ones for "power over fibre" with a laser at
the other end. I vaguely remember there being an example in AOE3.
I would love such a power optocoupler, if it were a reasonable size
and price.
There must be a market for a really quiet isolated dc/dc converter.
Maybe a sine wave thing.
[snip]
Yes I have been thinking about that, a really quiet DC-DC, e.g. with a magnetically-shielded transformer having both windings thoroughly electrostatically screened, or an optical isolator (but there is a worse limit to the efficiency for optical). The DC-DC inside Keithley
Sourcemeters is interesting in its construction though I have no idea
how well it performs.
Solar cells are cheap, and high-power IR LEDs are fairly cheap too, but
the combination won't be super-efficient nor small. If you want to avoid putting multiple solar cells in series, you could connect one solar cell
to a step-up transformer, and modulate the LED current so that there is
some AC for the transformer to step-up. To avoid DC in the windings you
could even put two solar cells in anti-parallel across the low voltage winding of the transformer, and illuminate the pair of solar cells
separately with two IR LEDs driven with opposite phase AC. Big solar
cells have a lot of capacitance though, so the frequency would have to
be lowish. If you want more isolation voltage, the light could be guided through a acrylic rods like a fat optical fibres. It'd be large, and not
as efficient as a transformer.
Hard-drive motors can run for a long time. Maybe you could make a motor-generator that lasts long enough. A little line-shaft across your
PCB for power distribution, with tiny flat belts to generators where you
need extra outputs. It'd look nice all made from ebonite and polished brass.
On Sun Apr 13 23:06:25 2025 Chris Jones wrote:of silica gel in the box to soak up moisture and the perovskites should last longer than you need them to.
On 12/04/2025 1:12 am, john larkin wrote:
On Fri, 11 Apr 2025 23:31:24 +1000, Chris Jones[snip]
<lugnut808@spam.yahoo.com> wrote:
On 11/04/2025 3:56 am, john larkin wrote:
The PVs are affordable and of course marvelously quiet, but they max >>>>> out typically below 100 uA. That gets tricky.
You can get more powerful ones for "power over fibre" with a laser at
the other end. I vaguely remember there being an example in AOE3.
I would love such a power optocoupler, if it were a reasonable size
and price.
There must be a market for a really quiet isolated dc/dc converter.
Maybe a sine wave thing.
Yes I have been thinking about that, a really quiet DC-DC, e.g. with a
magnetically-shielded transformer having both windings thoroughly
electrostatically screened, or an optical isolator (but there is a worse
limit to the efficiency for optical). The DC-DC inside Keithley
Sourcemeters is interesting in its construction though I have no idea
how well it performs.
Solar cells are cheap, and high-power IR LEDs are fairly cheap too, but
the combination won't be super-efficient nor small. If you want to avoid
putting multiple solar cells in series, you could connect one solar cell
to a step-up transformer, and modulate the LED current so that there is
some AC for the transformer to step-up. To avoid DC in the windings you
could even put two solar cells in anti-parallel across the low voltage
winding of the transformer, and illuminate the pair of solar cells
separately with two IR LEDs driven with opposite phase AC. Big solar
cells have a lot of capacitance though, so the frequency would have to
be lowish. If you want more isolation voltage, the light could be guided
through a acrylic rods like a fat optical fibres. It'd be large, and not
as efficient as a transformer.
If you hermetically seal the entire assembly in a metal box with feedthroughs, you could use perovskite solar cells for a nice bump in efficiency to lower the total area of cells you would need, and have great EMI shielding. Just include a little pkg
On 15/04/2025 13:47, Chris Jones wrote:
On 14/04/2025 3:40 am, Carl Ijames wrote:
On Sun Apr 13 23:06:25 2025 Chris Jones wrote:
On 12/04/2025 1:12 am, john larkin wrote:
On Fri, 11 Apr 2025 23:31:24 +1000, Chris Jones[snip]
<lugnut808@spam.yahoo.com> wrote:
On 11/04/2025 3:56 am, john larkin wrote:
The PVs are affordable and of course marvelously quiet, but they max >>>>>>> out typically below 100 uA. That gets tricky.
You can get more powerful ones for "power over fibre" with a laser at >>>>>> the other end. I vaguely remember there being an example in AOE3.
I would love such a power optocoupler, if it were a reasonable size
and price.
There must be a market for a really quiet isolated dc/dc converter.
Maybe a sine wave thing.
Yes I have been thinking about that, a really quiet DC-DC, e.g. with a >>>> magnetically-shielded transformer having both windings thoroughly
electrostatically screened, or an optical isolator (but there is a worse >>>> limit to the efficiency for optical). The DC-DC inside Keithley
Sourcemeters is interesting in its construction though I have no idea
how well it performs.
Solar cells are cheap, and high-power IR LEDs are fairly cheap too, but >>>> the combination won't be super-efficient nor small. If you want to avoid >>>> putting multiple solar cells in series, you could connect one solar cell >>>> to a step-up transformer, and modulate the LED current so that there is >>>> some AC for the transformer to step-up. To avoid DC in the windings you >>>> could even put two solar cells in anti-parallel across the low voltage >>>> winding of the transformer, and illuminate the pair of solar cells
separately with two IR LEDs driven with opposite phase AC. Big solar
cells have a lot of capacitance though, so the frequency would have to >>>> be lowish. If you want more isolation voltage, the light could be guided >>>> through a acrylic rods like a fat optical fibres. It'd be large, and not >>>> as efficient as a transformer.
If you hermetically seal the entire assembly in a metal box with
feedthroughs, you could use perovskite solar cells for a nice bump in
efficiency to lower the total area of cells you would need, and have
great EMI shielding. Just include a little pkg of silica gel in the
box to soak up moisture and the perovskites should last longer than
you need them to.
If you can choose the wavelength of illumination, there is no need to
use perovskites, as their ability to be tuned to match the spectrum of
sunlight has little benefit. I work with perovskite cells that stay in a
glove box full of very pure nitrogen (not me, I stay outside in the
air). Lots of things damage them, though they are getting better.
Interestingly, white LEDs don't like being inside the glove box in pure
nitrogen. They rapidly lose efficiency if they are operated in there,
but they recover if a little bit of oxygen is added (which we can't do,
because it harms the perovskites). So the LED solar simulator has to
stay outside. It has dozens of different LED wavelengths, some of them
are not bothered by being in nitrogen.
With an optical power isolator, the area of solar cells can be kept
small if the illumination can be prevented from spreading out much. So,
if a laser diode puts a few watts down a fibre, the receiving cell could
be tiny, perhaps only limited by not wanting it to melt.
It would be possible to couple a single high-powered fibre laser
to several photodiodes - perhaps connected in series to get a
more useful voltage - using a fibre beam splitter. Such
splitters are very cheap if you choose an infra-red wavelength
compatible with passive optical networking (GPON or XGPON) .
John
My TI rep was being difficult, so I just bought an eval board from
Digikey for $100.
It makes a nice 4.993 volt output, but it's wicked noisy.
https://www.dropbox.com/scl/fo/8fybyu5l3w4tdgt1y0386/AFunYi9K15UgNpkQzEbYaVA?rlkey=j261b4ca5kc966vq2y03fw0md&dl=0
53% efficient into that 0.25 watt load.
On 15/04/2025 19:40, Joe Gwinn wrote:
On Tue, 15 Apr 2025 15:17:58 +0100, John R Walliker
<jrwalliker@gmail.com> wrote:
On 15/04/2025 13:47, Chris Jones wrote:
On 14/04/2025 3:40 am, Carl Ijames wrote:
On Sun Apr 13 23:06:25 2025 Chris Jones wrote:
On 12/04/2025 1:12 am, john larkin wrote:
On Fri, 11 Apr 2025 23:31:24 +1000, Chris Jones[snip]
<lugnut808@spam.yahoo.com> wrote:
On 11/04/2025 3:56 am, john larkin wrote:I would love such a power optocoupler, if it were a reasonable size >>>>>>> and price.
The PVs are affordable and of course marvelously quiet, but they max >>>>>>>>> out typically below 100 uA. That gets tricky.
You can get more powerful ones for "power over fibre" with a laser at >>>>>>>> the other end. I vaguely remember there being an example in AOE3. >>>>>>>
There must be a market for a really quiet isolated dc/dc converter. >>>>>>> Maybe a sine wave thing.
Yes I have been thinking about that, a really quiet DC-DC, e.g. with a >>>>>> magnetically-shielded transformer having both windings thoroughly
electrostatically screened, or an optical isolator (but there is a worse >>>>>> limit to the efficiency for optical). The DC-DC inside Keithley
Sourcemeters is interesting in its construction though I have no idea >>>>>> how well it performs.
Solar cells are cheap, and high-power IR LEDs are fairly cheap too, but >>>>>> the combination won't be super-efficient nor small. If you want to avoid >>>>>> putting multiple solar cells in series, you could connect one solar cell >>>>>> to a step-up transformer, and modulate the LED current so that there is >>>>>> some AC for the transformer to step-up. To avoid DC in the windings you >>>>>> could even put two solar cells in anti-parallel across the low voltage >>>>>> winding of the transformer, and illuminate the pair of solar cells >>>>>> separately with two IR LEDs driven with opposite phase AC. Big solar >>>>>> cells have a lot of capacitance though, so the frequency would have to >>>>>> be lowish. If you want more isolation voltage, the light could be guided >>>>>> through a acrylic rods like a fat optical fibres. It'd be large, and not >>>>>> as efficient as a transformer.
If you hermetically seal the entire assembly in a metal box with
feedthroughs, you could use perovskite solar cells for a nice bump in >>>>> efficiency to lower the total area of cells you would need, and have >>>>> great EMI shielding. Just include a little pkg of silica gel in the >>>>> box to soak up moisture and the perovskites should last longer than
you need them to.
If you can choose the wavelength of illumination, there is no need to
use perovskites, as their ability to be tuned to match the spectrum of >>>> sunlight has little benefit. I work with perovskite cells that stay in a >>>> glove box full of very pure nitrogen (not me, I stay outside in the
air). Lots of things damage them, though they are getting better.
Interestingly, white LEDs don't like being inside the glove box in pure >>>> nitrogen. They rapidly lose efficiency if they are operated in there,
but they recover if a little bit of oxygen is added (which we can't do, >>>> because it harms the perovskites). So the LED solar simulator has to
stay outside. It has dozens of different LED wavelengths, some of them >>>> are not bothered by being in nitrogen.
With an optical power isolator, the area of solar cells can be kept
small if the illumination can be prevented from spreading out much. So, >>>> if a laser diode puts a few watts down a fibre, the receiving cell could >>>> be tiny, perhaps only limited by not wanting it to melt.
It would be possible to couple a single high-powered fibre laser
to several photodiodes - perhaps connected in series to get a
more useful voltage - using a fibre beam splitter. Such
splitters are very cheap if you choose an infra-red wavelength
compatible with passive optical networking (GPON or XGPON) .
John
Solar cells are silicon, which don't work at all with wavelengths
exceeding 900 nanometers, or shorter than about 500 nm.
Joe
Yes, but there are fibre-coupled detectors that work at longer
wavelengths. The only reason for using long wavelengths is that
there are lots of low-cost parts around (including fibre splitters)
that are used in GPON networks. The voltage per diode will of
course be lower with long wavelength devices.
John
#
It would be possible to couple a single high-powered fibre laser to
several photodiodes - perhaps connected in series to get a more useful >>voltage - using a fibre beam splitter. Such splitters are very cheap if >>you choose an infra-red wavelength compatible with passive optical >>networking (GPON or XGPON) . John
Solar cells are silicon, which don't work at all with wavelengths
exceeding 900 nanometers, or shorter than about 500 nm.
Joe
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