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low power, HV-in regulator with depletion mosfet

as

past.

situations.

it

I hate the conventional mosfet symbol. I draw them as BJTs with insulated gates. Oh, I hate the usual IGBT symbol, too.

Hey, this is suitably goofy:

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John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
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Reply to
John Larkin
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also

We await your list of "lethal hazards". Why are you so afraid of actually making a true engineering claim? You're a fraud. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85140   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Le Tue, 04 Jun 2013 12:29:36 -0400, Phil Hobbs a écrit:

There's that one and some others if you can stand the huge SO8 package and insanely low 10.6V BVDS abs max :

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Maybe you can photocopy the datasheet and loose the annoying dots...

Available at Mouser, not Joergly priced, but still affordable.

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Thanks, 
Fred.
Reply to
Fred Bartoli
[snip]

It may be possible on a single substrate, i.e. single body diode. I'm pondering, and will let the group know. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85140   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

It would be a useful product with many applications.

Failing that, I think there are two dies in the digital transistors which come in SOT-23 and smaller packages.

However, making it on a single chip would allow a chip scale type of construction which would help in getting the heat out in a fault condition. IIRC, the SOT-23 packages are marginal power-wise for high fault voltages, and there are two of them, so they share with an AC fault.

Reply to
Spehro Pefhany

as

past.

situations.

it

I like the old fashioned symbols too, because they remind me which way the body diode goes.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 USA 
+1 845 480 2058 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

past.

situations.

Series opposing, right. In normal operation, neither of the body diodes turns on, so they just look like resistors. Once you get up near I_DSS, one body diode does start to conduct, but the other FET provides the current limit.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 USA 
+1 845 480 2058 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

I'm done similar body-to-body structures, but in enhanced mode, to implement directional power switching. As in these previously posted links...

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I'll try it out with depletion mode and see what I get.

What catches my attention is the possibility to use such a gimmick as an HV DISCONNECT mechanism... rather than absorptive... ride it out.

I've done similar schemes in bipolar back in my alternator days... turn off the field device during a transient, and ride it out in BVcex mode. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85140   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Body-to-body works nicely, though some non-linearity in the "resistance" versus voltage, then you reach IDSS in either direction.

So a monolithic structure IS possible. You just need to convince someone to build it ;-)

What interests me is the series disconnect connection in conjunction with the usual ESD diodes... perfect performance between rails, then limited current into the ESD structure. I have several monolithic processes available to me now that have depletion devices, so I get to play >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85140   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

formatting link 

--

John Larkin         Highland Technology, Inc 

jlarkin at highlandtechnology dot com 
http://www.highlandtechnology.com 

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom laser drivers and controllers 
Photonics and fiberoptic TTL data links 
VME thermocouple, LVDT, synchro   acquisition and simulation
Reply to
John Larkin

zener modulating Vgs of the FET. I'm not going to speculate about a bunch of what-if's as to what kind of environment the circuit has to tolerate, just too open ended. The original post said something about just 10mA load or so and a

48V supply, so that means he can easily power limit his source to something workable and eliminate all this crazy conjecture about spikes, blown junctions, unlimited rise times, and megalithic energy storage reservoirs all over the place ready to unleash destruction.

Smoke is fine, it lets you know there is fire in the wire..

But really, how about a soft start on that cap? As you said, current limit is unknown, that could upset the customers supply if it is also operating other items?

Just thinking out load.

Jamie

Reply to
Jamie

I use Dep-fets on inputs of devices that only supply a resistor if you want to use the device in current mode. It's easy for some current transmitter to short or a stupid pulled.

I think JL was the one that through me the bone on that one some time back when I was looking for a cheap in line current limiter.

Jfets were also an option but not too many in the low R range.

Jamie

Reply to
Jamie 

--
Facts often matter very little to you when you're confronted with the 
proposition that you've made an error, and you'll go to any lengths in 
order to make that proposition seem wrong.  

Kind of like if you were in a race where you were running 
neck-and-neck for a while with your competition, and then when you 
started to slow down and he started pulling ahead, you tripped him and 
won the race.
Reply to
John Fields

What a jerk you are.

--

John Larkin         Highland Technology, Inc 

jlarkin at highlandtechnology dot com 
http://www.highlandtechnology.com 

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom laser drivers and controllers 
Photonics and fiberoptic TTL data links 
VME thermocouple, LVDT, synchro   acquisition and simulation
Reply to
John Larkin

S as

ts

he past.

ituations.

n
k

ext -

r

Thanks, So it takes -1V (or so) to turn it off. (looking at the data sheet with 'new' eyes.) I guess the best thing is to just order a few.

For input protection I've only done the series (~1k) resistor and diodes to the power rails... which also has 'issues'.

George H.

t -

Reply to
George Herold

but also

I just browsed through the app note. $^&#($%($&^#^&)#^^& OMFH Every one of those circuits is a bad design. They look like a summer intern with no experience grade foolishness. Take figure 11, i don't see how to turn the FET off enough for it to work. It would require 4 volts across R2 at zero load current. A normal (enhancement) fet would work just fine.

?-)

Reply to
josephkk

Yep. Just make sure that U2-A,B have ESD diodes. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85140   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

.

That particular circuit originated with Advanced Linear Devices which produ ces depletion MOSFETs with very low thresholds like -0.2V and have fairly l ow currents at VGS=0, uA level. The choice of a depletion FET in a low vo ltage application buys you headroom you would lose using an enhancement FET .

Reply to
bloggs.fredbloggs.fred

also

Yeah, that Ixys appnote is horrible.

--

John Larkin         Highland Technology, Inc 

jlarkin at highlandtechnology dot com 
http://www.highlandtechnology.com 

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom laser drivers and controllers 
Photonics and fiberoptic TTL data links 
VME thermocouple, LVDT, synchro   acquisition and simulation
Reply to
John Larkin

Not nearly as horrible as your "regulator" suggestion...

Reply to
bloggs.fredbloggs.fred

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