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Re: LS/HCT/etc. logic familes
On 2017-07-15 13:30, John Larkin wrote:
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In your case that is certainly the right strategy. On many of my designs  
I have to pinch pennies. Once I designed a nice TDR for a client which  
ran under $10 in production and I felt real good about the results. Then  
the client called and asked "Well, it is a really nice design but, ahem,  
how shall I say, could you design another one that is maybe only 80% as  
good but costs under $5?".


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Yes, though I am usually after more oomph. 10 amp range and Rdson values  
or equivalents in the 1 ohm vicinity.

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: LS/HCT/etc. logic familes
wrote:

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New part:

https://www.eeweb.com/company-news/ixys/new-low-cost-dual-5a-gate-driver-ic

Dual 5 amps, 20 volts, 7 ns r/f, about 1 ohm each driver, 44 cents in
quantity.

Might be nice in a dc/dc converter too. Drive a transformer directly.



--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: LS/HCT/etc. logic familes
On 2017-07-15 17:02, John Larkin wrote:
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Buy one - get one free, and ohm-range for Rdson. Great! Thanks.


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With 20V abs max for VCC that may be a nice use for it.

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: LS/HCT/etc. logic familes
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The IXYS drivers go all the way up to 30A.  Maybe they have a bigger one  
now, too.

I used the 15A versions years ago to drive IGBT modules (+/-15V), no  
problem.

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
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Re: LS/HCT/etc. logic familes
On Tuesday, July 11, 2017 at 9:49:07 PM UTC+2, Tim Williams wrote:
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Maybe I am getting it wrong, but are you driving the FET gate directly with one logic part, and driving the same FET gate with a emitter follower stage?

Cheers

Klaus

Re: LS/HCT/etc. logic familes
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Yes,
https://www.seventransistorlabs.com/Images/BoostedLogicGateDrive.png

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
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Re: LS/HCT/etc. logic familes
On Wednesday, July 12, 2017 at 3:01:20 AM UTC+2, Tim Williams wrote:
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It's nice

But, won't you get momentary shorting of the gate due to the "propagation delay" in the emitter followers? But I guess that part can handle a brief short of the output...

Cheers

Klaus

Re: LS/HCT/etc. logic familes
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Won't you get "momentary shorting" driving a capacitance in the first place?  
Or a transmission line*?  ;-)

(*No.  A transmission line /is/ actually a resistance, until stuff reflects  
down it, that is. :) )

The "delay" of an emitter follower is very small, actually; at most, it's  
the forward recovery of the B-E junction, negligible to HC logic (fractional  
ns?).  It manifests as an R || C, as far as the gate is concerned. :)

The interesting observation to make, is that the gate is ultimately a  
"complementary" pair of transistors driving a node.  The limit is thermal  
only*.  They're _absolutely fine_ driving a short for, eh... milliseconds at  
a time?

(In practice, you can get away with shorting logic outputs for indeterminate  
time periods.  It's not /recommended/, but you can get away with it.)

Indeed, the follower /helps/ the direct-connected one, by forcing the load  
along.  Where it would be dumping into a large (in my case 4nF) capacitance  
for hundreds of nanoseconds, instead it's only doing it for 50ns.

By the same reasoning: it's not recommended to parallel Schmitt trigger  
gates (HC14 in my case), but in practice, they're /monolithically matched/,  
so they'll all transition within fractions of a nanosecond, and even if they  
don't, they'll only be "fighting" each other for that same fraction of a  
nanosecond.

The underlying lesson being: digital theory** is great for static  
validation, but when it becomes necessary to take a hard, up-close look at  
it -- on scales similar to the rise or propagation times of the gates -- it  
fails to be representative of the real device physics, and we must go back  
to analog analysis methods instead.  That is to say: I may be using 74HC  
gates, but it's an analog circuit. :-)

(**That is, the connectivity rules and event based time-domain analysis that  
most digital simulators employ.)

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
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Re: LS/HCT/etc. logic familes
wrote:

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Here's a 100 volt pulse into a 50 ohm load, transformer coupled. The
fet gate drivers are TinyLogic triple buffers, 13 cents each.

https://dl.dropboxusercontent.com/u/53724080/Circuits/Fast_Stuff/HV_100v_Pulse.jpg

One trick is to run them at abs max Vcc.



--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: LS/HCT/etc. logic familes
On 2017-07-11 13:15, John Larkin wrote:
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... and not pump out too many pulses per second. Otherwise the plastic  
package might start to bubble and smell funky.

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: LS/HCT/etc. logic familes
On 11/07/2017 17:55, snipped-for-privacy@gmail.com wrote:
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40109 level shifter

piglet


Re: LS/HCT/etc. logic familes
On Tue, 11 Jul 2017 09:55:24 -0700 (PDT), snipped-for-privacy@gmail.com
wrote:

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Level shifters...

   <http://www.analog-innovations.com/SED/LevelTranslator.pdf>


<http://www.analog-innovations.com/SED/LogicLevelTranslator74HC14-RevA.pdf>

   <http://www.analog-innovations.com/SED/LogicLevelTranslator.pdf>
        
                                        ...Jim Thompson
--  
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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Re: LS/HCT/etc. logic familes
wrote:

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Yep.  74HC4xxx versions of the old-line 4000-series are readily
available.

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                                        ...Jim Thompson
--  
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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Re: LS/HCT/etc. logic familes
On 2017-07-11 10:15, Jim Thompson wrote:
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Even the CD4000 series is. They are essential in many apps where you do  
not have a well regulated supply or where the supply consist of a 9V  
battery. Or alarm systems and such with a 12V battery. There you can't  
use 74HC.

Any (hopefully good) news on your health?

[...]

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: LS/HCT/etc. logic familes
wrote:

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CT-Scan on the 19th.
        
                                        ...Jim Thompson
--  
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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Re: LS/HCT/etc. logic familes
On Tue, 11 Jul 2017 10:58:54 -0700, the renowned Jim Thompson

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Fingers crosssed.  

--sp  

--  
Best regards,  
Spehro Pefhany

Re: LS/HCT/etc. logic familes
On Tue, 11 Jul 2017 19:02:52 -0400, Spehro Pefhany

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I have a positive outlook.  But I could be wrong.
        
                                        ...Jim Thompson
--  
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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Re: LS/HCT/etc. logic familes
Joerg wrote:
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IIRC 74C (not HC) also had a supply range like 4000.




Re: LS/HCT/etc. logic familes
On 2017-07-19 19:27, Tom Del Rosso wrote:
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Yes, but they are gone.

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: LS/HCT/etc. logic familes
wrote:

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A uC needs a program, which needs to be properly documented and
formally released. Then each chip needs to be programmed. That can
cost kilobucks, so it will take a lot of production units to justify
that. A few MSI chips is often the pragmatic way to get things done.




--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


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