>On Tuesday, September 20, 2022 at 6:35:12 PM UTC-7, John Larkin wrote:
>> On Tue, 20 Sep 2022 18:23:56 -0700 (PDT), whit3rd <whi...@gmail.com>
>> wrote:
>> >On Tuesday, September 20, 2022 at 11:04:11 AM UTC-7, John Larkin wrote:
>> >> I want lots of voltage drop at 100 mA or so.
>> >>
>> >> A high voltage fast-recovery diode, like ES1G, might work.
>> >
>> >Or, a diode and 10 ohm resistor in series.
>> >
>> >The structure of a PIN diode should give fairly high forward resistivity,
>> >though I'm not sure where that'd be found in a datasheet.
>> HV diodes are usually PINs. That shows up in the I:V curve.
>
>For example, BYT62, from Vishay? It does seem to have the
>high forward voltage, and 2.4 kV breakdown...
That looks like a stack, probably three junctions.
Reply by whit3rd●September 22, 20222022-09-22
On Tuesday, September 20, 2022 at 6:35:12 PM UTC-7, John Larkin wrote:
> On Tue, 20 Sep 2022 18:23:56 -0700 (PDT), whit3rd <whi...@gmail.com>
> wrote:
> >On Tuesday, September 20, 2022 at 11:04:11 AM UTC-7, John Larkin wrote:
> >> I want lots of voltage drop at 100 mA or so.
> >>
> >> A high voltage fast-recovery diode, like ES1G, might work.
> >
> >Or, a diode and 10 ohm resistor in series.
> >
> >The structure of a PIN diode should give fairly high forward resistivity,
> >though I'm not sure where that'd be found in a datasheet.
> HV diodes are usually PINs. That shows up in the I:V curve.
For example, BYT62, from Vishay? It does seem to have the
high forward voltage, and 2.4 kV breakdown...
Reply by John Larkin●September 21, 20222022-09-21
On Tue, 20 Sep 2022 19:13:19 -0400, Carl <carl.ijamesxx@yyverizon.net>
wrote:
>On 9/20/22 17:20, John Larkin wrote:
>> On Tue, 20 Sep 2022 13:46:39 -0700 (PDT), Fred Bloggs
>> <bloggs.fredbloggs.fred@gmail.com> wrote:
>>
>>> On Tuesday, September 20, 2022 at 2:04:11 PM UTC-4, John Larkin wrote:
>>>> I want lots of voltage drop at 100 mA or so.
>>>>
>>>> A high voltage fast-recovery diode, like ES1G, might work.
>>>>
>>>> I suppose I could just put two ES1Gs in series, but that's not
>>>> sporting.
>>>>
>>>> MMBD5004S is two wimpy diodes in series, in SOT-23. That would drop
>>>> about 2 volts at 100 mA!
>>>>
>>>> This is a supply sequencing dilemma with the LT6803. A long story.
>>>
>>> Think of some other way. Diode solutions aren't all they're cracked up to be.
>>
>> I just need to drop about a volt. A diode would do that just fine.
>> Better yet 2 diodes in series so I can tune the drop.
>>
>> https://www.dropbox.com/s/j72tytvzae0ubf2/T660_Regs_Sep_20.jpg?raw=1
>>
>> Reg3 has an abs max input of 6 volts. I want at least 6.5 for my
>> linear regs. I can't use 3.3 as the input to reg3 because +1 FPGA core
>> has to come up before 3.3.
>>
>
>resistor and 5ish volt zener to ground?
Zener regs are very inefficient. The resistor has to be sized for the
max load current, and any less is burned up all the time.
A zener and emitter follower would work. Or a chunky emitter follower
off my +5 supply.
Reply by John Larkin●September 21, 20222022-09-21
On Wed, 21 Sep 2022 08:38:43 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:
>tirsdag den 20. september 2022 kl. 23.20.55 UTC+2 skrev John Larkin:
>> On Tue, 20 Sep 2022 13:46:39 -0700 (PDT), Fred Bloggs
>> <bloggs.fred...@gmail.com> wrote:
>>
>> >On Tuesday, September 20, 2022 at 2:04:11 PM UTC-4, John Larkin wrote:
>> >> I want lots of voltage drop at 100 mA or so.
>> >>
>> >> A high voltage fast-recovery diode, like ES1G, might work.
>> >>
>> >> I suppose I could just put two ES1Gs in series, but that's not
>> >> sporting.
>> >>
>> >> MMBD5004S is two wimpy diodes in series, in SOT-23. That would drop
>> >> about 2 volts at 100 mA!
>> >>
>> >> This is a supply sequencing dilemma with the LT6803. A long story.
>> >
>> >Think of some other way. Diode solutions aren't all they're cracked up to be.
>> I just need to drop about a volt. A diode would do that just fine.
>> Better yet 2 diodes in series so I can tune the drop.
>
>NPN and two resistors?
That would work, but is more parts than two diodes. I'd probably need
something bigger than a SOT23.
Reply by John Larkin●September 21, 20222022-09-21
On Wed, 21 Sep 2022 16:19:14 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:
>On a sunny day (Wed, 21 Sep 2022 07:34:49 -0700) it happened John Larkin
><jlarkin@highlandSNIPMEtechnology.com> wrote in
><d58mih9ta0jghuks7ibflhguba17jim6bl@4ax.com>:
>
>>On Wed, 21 Sep 2022 05:04:36 GMT, Jan Panteltje
>><pNaonStpealmtje@yahoo.com> wrote:
>>
>>>On a sunny day (Tue, 20 Sep 2022 11:04:03 -0700) it happened John Larkin
>>><jlarkin@highlandSNIPMEtechnology.com> wrote in
>>><akvjih1eeavtfqhlb82igfe28tvg8br8i5@4ax.com>:
>>>
>>>>I want lots of voltage drop at 100 mA or so.
>>>>
>>>>A high voltage fast-recovery diode, like ES1G, might work.
>>>>
>>>>I suppose I could just put two ES1Gs in series, but that's not
>>>>sporting.
>>>>
>>>>MMBD5004S is two wimpy diodes in series, in SOT-23. That would drop
>>>>about 2 volts at 100 mA!
>>>>
>>>>This is a supply sequencing dilemma with the LT6803. A long story.
>>>
>>>Old color sets had a 4 kV rectfer for focus, consisted
>>> of a ceramic tube with a zillion ? diodes in series
>>> https://www.ebay.com/itm/192966681173?hash=item2cedb5e255:g:FqgAAOSwxhNjE38d&_trksid=p5731.m3795
>>> https://www.ebay.com/itm/194844748455
>>>
>>>;-)
>>
>>I think one plate/junction of a selenium rectifier dropped about 2
>>volts.
>
>You could make something with a transistor Vbe and diode in series:
> |
> ___
> \ /
> ---
> |
> _________
> | |
> | |
>[ ] X |c
> | |/
> |------| NPN
> | |\/e
>[ ] 1k |
> | |
> ---------
> |
Yes, there are lots of ways to use a transistor here. Don't need the
upper series diode.
A small Darlington would give me more drop. Or one of those "logic
transistors" with internal resistors.
The only darls we have in stock are ancient TO-92, hand load and
solder stuff. Yuk. Mosfets pretty much made darlingtons obsolete.
A logic-threshold mosfet like FDV301, drain to gate, would sort of
work. Roughly 2 volts at 200 mA; 400 mW is a bit much for a SOT23.
Reply by Jan Panteltje●September 21, 20222022-09-21
On a sunny day (Wed, 21 Sep 2022 07:34:49 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<d58mih9ta0jghuks7ibflhguba17jim6bl@4ax.com>:
>On Wed, 21 Sep 2022 05:04:36 GMT, Jan Panteltje
><pNaonStpealmtje@yahoo.com> wrote:
>
>>On a sunny day (Tue, 20 Sep 2022 11:04:03 -0700) it happened John Larkin
>><jlarkin@highlandSNIPMEtechnology.com> wrote in
>><akvjih1eeavtfqhlb82igfe28tvg8br8i5@4ax.com>:
>>
>>>I want lots of voltage drop at 100 mA or so.
>>>
>>>A high voltage fast-recovery diode, like ES1G, might work.
>>>
>>>I suppose I could just put two ES1Gs in series, but that's not
>>>sporting.
>>>
>>>MMBD5004S is two wimpy diodes in series, in SOT-23. That would drop
>>>about 2 volts at 100 mA!
>>>
>>>This is a supply sequencing dilemma with the LT6803. A long story.
>>
>>Old color sets had a 4 kV rectfer for focus, consisted
>> of a ceramic tube with a zillion ? diodes in series
>> https://www.ebay.com/itm/192966681173?hash=item2cedb5e255:g:FqgAAOSwxhNjE38d&_trksid=p5731.m3795
>> https://www.ebay.com/itm/194844748455
>>
>>;-)
>
>I think one plate/junction of a selenium rectifier dropped about 2
>volts.
You could make something with a transistor Vbe and diode in series:
|
___
\ /
---
|
_________
| |
| |
[ ] X |c
| |/
|------| NPN
| |\/e
[ ] 1k |
| |
---------
|
Reply by Lasse Langwadt Christensen●September 21, 20222022-09-21
tirsdag den 20. september 2022 kl. 23.20.55 UTC+2 skrev John Larkin:
> On Tue, 20 Sep 2022 13:46:39 -0700 (PDT), Fred Bloggs
> <bloggs.fred...@gmail.com> wrote:
>
> >On Tuesday, September 20, 2022 at 2:04:11 PM UTC-4, John Larkin wrote:
> >> I want lots of voltage drop at 100 mA or so.
> >>
> >> A high voltage fast-recovery diode, like ES1G, might work.
> >>
> >> I suppose I could just put two ES1Gs in series, but that's not
> >> sporting.
> >>
> >> MMBD5004S is two wimpy diodes in series, in SOT-23. That would drop
> >> about 2 volts at 100 mA!
> >>
> >> This is a supply sequencing dilemma with the LT6803. A long story.
> >
> >Think of some other way. Diode solutions aren't all they're cracked up to be.
> I just need to drop about a volt. A diode would do that just fine.
> Better yet 2 diodes in series so I can tune the drop.
>On Tuesday, September 20, 2022 at 9:33:17 PM UTC-4, John Larkin wrote:
>> On Wed, 21 Sep 2022 01:22:36 +0300, Dimiter_Popoff <d...@tgi-sci.com>
>> wrote:
>>
>> >On 9/21/2022 0:59, John Larkin wrote:
>> >> On Wed, 21 Sep 2022 00:13:29 +0300, Dimiter_Popoff <d...@tgi-sci.com>
>> >> wrote:
>> >>
>> >>> On 9/20/2022 21:04, John Larkin wrote:
>> >>>> I want lots of voltage drop at 100 mA or so.
>> >>>>
>> >>>> A high voltage fast-recovery diode, like ES1G, might work.
>> >>>>
>> >>>> I suppose I could just put two ES1Gs in series, but that's not
>> >>>> sporting.
>> >>>>
>> >>>> MMBD5004S is two wimpy diodes in series, in SOT-23. That would drop
>> >>>> about 2 volts at 100 mA!
>> >>>>
>> >>>> This is a supply sequencing dilemma with the LT6803. A long story.
>> >>>>
>> >>>
>> >>> I am sure you'll find your way with the problem calling for the
>> >>> diode without any help.
>> >>
>> >> It's an electronic discussion group! In theory at least. Sometimes.
>> >
>> >I was just making an excuse for the rant I was about to post, of course
>> >I did not mean your post was inappropriate, quite the contrary.
>> >
>> >>
>> >>> I am going to insert a rant-ish comment about the "long story".
>> >>>
>> >>> Every time I have used some readily available convertor part,
>> >>> LTC, Maxim many ears earlier, there were long stories.
>> >>> Which is why to this day I make my own regulators, 1/2 74hc123
>> >>> and 1/2 lmc6482, typically. Plus a mosfet and its driver of course.
>> >>> Somewhat more complex and the story may be long again on
>> >>> some occasions but the ending is happy and calls for a lot
>> >>> less compromise. Having control over the loop overall etc.
>> >>> gives you that.
>> >>
>> >> Home-made is a lot of parts. Lots of integrated switchers work fine.
>> >
>> >They take more part obviously but they don't take a much larger area
>> >on the board. I am sure lots of integrated switchers work fine, and
>> >the few (not more than 5-6) I remember using did work but had either
>> >stability issues or noise or whatever, I don't remember, I only
>> >remember there were issues beyond my control as they were integrated.
>> >I may have been too demanding, of course.
>> >
>> >>
>> >> Synchronous switchers can have bad EMI issues.
>> >>
>> >> Some parts are poorly defined as regards cap ESR and loop stability.
>> >>
>> >> Best to breadboard.
>> >>
>> >
>> >Breadboard does not help much with switchers where routing is essential.
>> >But I have found out that even for my "home made" switchers ltspice is
>> >reasonably accurate evaluating stability over load and input variations,
>> >as well as step response etc.
>> I really like TPS54302. It's a tiny SOT23 switcher, spread-spectrum,
>> well behaved. But I can't get the TI Pspice model to work in LT Spice
>> and I haven't the energy to learn Tina. I'll breadboard it.
>>
>> I think I can use it as a +7 to -7 converter.
>
>
>https://webench.ti.com/power-designer/switching-regulator/export/217?noparams=0
>Export LM25088MH-1/NOPB ? 7V-7V to -7.00V @ 2A
>
>cheers
Webench requires a login (why make people log in to sell stuff?) and
doesn't work on my machines.
I suspect that LT Spice added a couple billion dollars to ADI's
purchase price of LT. And it crushed the sales of several expensive
simulators. Mike E says that LT Spice is used 1000 times more than all
other circuut sim programs.
There are advantages to breadboarding tricky stuff like switchers,
even if the sims work. EMI. Thermals. Caps. Inductors. Reality.
https://www.dropbox.com/sh/ajtqs7c1nswfhey/AABi7r0gchljjrxka4aHZItfa?dl=0https://www.dropbox.com/sh/8nd4dibu77znh44/AAAkO6lEHy9FZ50od2-mqt0va?dl=0
Actually, I have a LOT of test data on TPS54302, just none for the
inverter case.
Someone used to sell a pseudorandom noise generator chip. This is one!
Reply by John Larkin●September 21, 20222022-09-21
On Wed, 21 Sep 2022 05:04:36 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:
>On a sunny day (Tue, 20 Sep 2022 11:04:03 -0700) it happened John Larkin
><jlarkin@highlandSNIPMEtechnology.com> wrote in
><akvjih1eeavtfqhlb82igfe28tvg8br8i5@4ax.com>:
>
>>I want lots of voltage drop at 100 mA or so.
>>
>>A high voltage fast-recovery diode, like ES1G, might work.
>>
>>I suppose I could just put two ES1Gs in series, but that's not
>>sporting.
>>
>>MMBD5004S is two wimpy diodes in series, in SOT-23. That would drop
>>about 2 volts at 100 mA!
>>
>>This is a supply sequencing dilemma with the LT6803. A long story.
>
>Old color sets had a 4 kV rectfer for focus, consisted
> of a ceramic tube with a zillion ? diodes in series
> https://www.ebay.com/itm/192966681173?hash=item2cedb5e255:g:FqgAAOSwxhNjE38d&_trksid=p5731.m3795
> https://www.ebay.com/itm/194844748455
>
>;-)
I think one plate/junction of a selenium rectifier dropped about 2
volts.
Reply by Jan Panteltje●September 21, 20222022-09-21
On a sunny day (Tue, 20 Sep 2022 11:04:03 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<akvjih1eeavtfqhlb82igfe28tvg8br8i5@4ax.com>:
>I want lots of voltage drop at 100 mA or so.
>
>A high voltage fast-recovery diode, like ES1G, might work.
>
>I suppose I could just put two ES1Gs in series, but that's not
>sporting.
>
>MMBD5004S is two wimpy diodes in series, in SOT-23. That would drop
>about 2 volts at 100 mA!
>
>This is a supply sequencing dilemma with the LT6803. A long story.