No relatively expensive high side current monitor, comparator or latch ICs either. You're wasting your time and money using these items if all you need is a fast electronic "fuse". A single BJT, in conjunction with the MOSFET, is all that is required for UVLO, overcurrent and short circuit protection. Throw in a voltage reference, like the TL431, if the switch has to cover a wide voltage range.
I sort of doubt it.
John
Post a schematic or show a link. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
The only thing bipartisan in this country is hypocrisy
That's okay. Forgot to add >
Oh sure!
>
Still doubt it. Show us.
John
We'd be happy to analyze your circuit, and point out where it fails to do what you think its doing.
--
Thanks,
- Win
"oparr" doesn't know he's about to bite the dust and look like an idiot ;-) ...Jim Thompson
-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at
-- If you're not prepared to show your work, what was the purpose of the original post? JF
Well, there's >
There are well kept secrets in everyday electronics.
>
-- That's certainly true, but keeping those secrets safe usually involves maintaining a low profile and not blabbing about them in public. "Loose lips sink ships", you know, so, again, what was the purpose of the original post? JF
He's a Larkin spin-off... allusions/illusions of grandeur :-) ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
The only thing bipartisan in this country is hypocrisy
Since you won't reveal your circuit, maybe you can explain your business model to us.
John
He can do most of that (if he's prepared to be crappy enough) by using one of those beta-dependent BJT circuits of yours--stick a BJT in series with the source of the MOSFET, and give it just enough base current to almost saturate at the highest current you want to allow.
NOT how you'd want to do it in real life, but it'd limit the current and so on.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
That would work at the microamp sort of level. Not very useful.
The thing I like about beta limiting, in addition to its electrical virtues, is that everybody has been taught many, many times to never, never do it. I can't pass up a challenge like that. People who will cheerfully use a jfet with 10:1 Idss ratings won't consider beta design using a BCX71K with a less than 2:1 HFE spread.
I really like the Supertex depletion fets as signal-level protectors.
John
Yep. Larkin's magic bag of tricks can certainly give one heartburn ;-) ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
The only thing bipartisan in this country is hypocrisy
Hell! I regularly design around PNP's with a worst-case beta of 1 (yep, one!)
I love chip processes that have depletion-mode FET's... just great for Bandgap starters. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
The only thing bipartisan in this country is hypocrisy
Don't all fabs have JFETs? Maybe not defined and 'scoped out, but aren't they at least able to accommodate them if you roll your own?
--
Thanks,
- Win
Some fabs have an N-well resistor that is sort of a JFET. The problem is you want one that cuts off sharply enough that start-up goes away completely. I've only seen a few useable for low voltage circuits, such as in RFID tags. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
The only thing bipartisan in this country is hypocrisy
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