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From: Jan Panteltje on 11 May 2010 18:55
On a sunny day (Tue, 11 May 2010 11:09:15 -0400) it happened Spehro Pefhany
<speffSNIP(a)interlogDOTyou.knowwhat> wrote in
<pmsiu5lgns06si5pql6tdfuohroam4kqju(a)4ax.com>:

>On Tue, 11 May 2010 14:21:58 GMT, Jan Panteltje
><pNaonStpealmtje(a)yahoo.com> wrote:
>
>>But that cannot beat, but only augment something like his:
>> http://panteltje.com/panteltje/pic/freq_pic/index.html
>>Everything has its use.
>
>It would be interesting to see how the 18FxxKxx would do in that
>circuit. I'm guessing >150MHz typically.

150 MHz, radio hams would like that for 144 MHz.
Maybe one of thsoe days....

From: JosephKK on 12 May 2010 00:16
On Tue, 11 May 2010 00:29:25 -0700 (PDT), Didi <dp(a)tgi-sci.com> wrote:

>On May 11, 6:33 am, legg <l...(a)nospam.magma.ca> wrote:
>> On Mon, 10 May 2010 09:53:57 -0700 (PDT), Didi <d...(a)tgi-sci.com> wrote:
>> >Not so long ago I put them in a design (the other Microchip part which
>> >has
>> >made it into my designs is an I2C EEPROM).
>> >Worked as expected while driving tiny MOSFETs (two in an SO-8).
>>
>> >But when it came to an IRF540 - plain old IRF540 - they failed
>> >miserably.
>> >I first looked at them driving the IRF "empty", i.e. the drain
>> >hanging, source
>> >practically grounded (well, via 0.1 Ohm or so). Never got past this
>> >with this
>> >driver.
>>
>> >The edges got really bad - 500 nS if not worse, way beyond spec. I
>> >checked
>> >what happened with a series 10 Ohm resistor, nothing worth noting. OK,
>> >at
>> >the driver output the initial perhaps 1/5th or 1/4th of the voltage
>> >excursion
>> >got better.
>>
>> >Before I began trying things out etc. I replaced the TC4426 with a
>> >good old
>> >MC33151. Worked same as it has worked last 20+ years for me, well
>> >under
>> >100 nS (was something about 50-60).
>>
>> >I did not pursue it further, there was no point stopping at it. Got it
>> >working
>> >with the 33151, which was designed in times when apparently someone
>> >would have noticed if a design did not work :-).
>>
>> >But a few days later I am still curious what was that. Looked as if
>> >some
>> >foldback current limiting - wanted by the designer or not - took
>> >effect, perhaps
>> >I could have eliminated it with a larger current limiting resistor so
>> >things would
>> >get usable (much worse than with the 33151, obviously, it would have
>> >taken
>> >perhaps 50+ Ohm).
>>
>> >Any thoughts?
>>
>> >Dimiter
>>
>> As was related in an earlier thread, the input hysterisis of the 4426
>> and similar parts is not enforced on the input signal pin, but after a
>> linear input stage comprised of an nmos fet. This means that input
>> hysterisis cannot be specified for these parts as a percentage of the
>> input signal logic level - so input noise and ground bounce on the
>> devices' supply pins may be an issue.
>
>Well the input is 5V CMOS, well below 10 nS edge. If that is not
>enough for them I can't imagine what is.
>Ground bounce if any will be solely inside the chip, like I explained
>in an earlier post a 1206 1uF (ceramic) is pinned to the power/GND
>pins, at the bottom side of the board. The connecting vias also
>connect the thing to the power/GND planes respectively.
>So it is neither of these, I would not have posted this if things
>were that easy :-).
>
>> In a dual driver situation, you might even find that one driver is
>> upsetting the other, so check the the input and output state of the
>> static side when the funny behavior is occuring on the other. There
>> may be symptoms there, that you wouldn't normally look for, or expect.
>
>The other driver is driven and unused. Does not change state at
>all, the input is either 0 or 5V (don't remember which it was).
>Nothing worth noting at it.


I would have "paralleled" the two with individual 10R to the gate.
>
>Dimiter
>
>------------------------------------------------------
>Dimiter Popoff Transgalactic Instruments
>
>http://www.tgi-sci.com
>------------------------------------------------------
>http://www.flickr.com/photos/didi_tgi/sets/72157600228621276/
>
From: Didi on 12 May 2010 06:36
On May 12, 7:16 am, "JosephKK"<quiettechb...(a)yahoo.com> wrote:
> On Tue, 11 May 2010 00:29:25 -0700 (PDT), Didi <d...(a)tgi-sci.com> wrote:
> >On May 11, 6:33 am, legg <l...(a)nospam.magma.ca> wrote:
> >> On Mon, 10 May 2010 09:53:57 -0700 (PDT), Didi <d...(a)tgi-sci.com> wrote:
> >> >Not so long ago I put them in a design (the other Microchip part which
> >> >has
> >> >made it into my designs is an I2C EEPROM).
> >> >Worked as expected while driving tiny MOSFETs (two in an SO-8).
>
> >> >But when it came to an IRF540 - plain old IRF540 - they failed
> >> >miserably.
> >> >I first looked at them driving the IRF "empty", i.e. the drain
> >> >hanging, source
> >> >practically grounded (well, via 0.1 Ohm or so). Never got past this
> >> >with this
> >> >driver.
>
> >> >The edges got really bad - 500 nS if not worse, way beyond spec. I
> >> >checked
> >> >what happened with a series 10 Ohm resistor, nothing worth noting. OK,
> >> >at
> >> >the driver output the initial perhaps 1/5th or 1/4th of the voltage
> >> >excursion
> >> >got better.
>
> >> >Before I began trying things out etc. I replaced the TC4426 with a
> >> >good old
> >> >MC33151. Worked same as it has worked last 20+ years for me, well
> >> >under
> >> >100 nS (was something about 50-60).
>
> >> >I did not pursue it further, there was no point stopping at it. Got it
> >> >working
> >> >with the 33151, which was designed in times when apparently someone
> >> >would have noticed if a design did not work :-).
>
> >> >But a few days later I am still curious what was that. Looked as if
> >> >some
> >> >foldback current limiting - wanted by the designer or not - took
> >> >effect, perhaps
> >> >I could have eliminated it with a larger current limiting resistor so
> >> >things would
> >> >get usable (much worse than with the 33151, obviously, it would have
> >> >taken
> >> >perhaps 50+ Ohm).
>
> >> >Any thoughts?
>
> >> >Dimiter
>
> >> As was related in an earlier thread, the input hysterisis of the 4426
> >> and similar parts is not enforced on the input signal pin, but after a
> >> linear input stage comprised of an nmos fet. This means that input
> >> hysterisis cannot be specified for these parts as a percentage of the
> >> input signal logic level - so input noise and ground bounce on the
> >> devices' supply pins may be an issue.
>
> >Well the input is 5V CMOS, well below 10 nS edge. If that is not
> >enough for them I can't imagine what is.
> >Ground bounce if any will be solely inside the chip, like I explained
> >in an earlier post a 1206 1uF (ceramic) is pinned to the power/GND
> >pins, at the bottom side of the board. The connecting vias also
> >connect the thing to the power/GND planes respectively.
> >So it is neither of these, I would not have posted this if things
> >were that easy :-).
>
> >> In a dual driver situation, you might even find that one driver is
> >> upsetting the other, so check the the input and output state of the
> >> static side when the funny behavior is occuring on the other. There
> >> may be symptoms there, that you wouldn't normally look for, or expect.
>
> >The other driver is driven and unused. Does not change state at
> >all, the input is either 0 or 5V (don't remember which it was).
> >Nothing worth noting at it.
>
> I would have "paralleled" the two with individual 10R to the gate.

Well so would have I, but the unused one will not be that forever.
It will drive another gate when things get that far :-) . The FET
is not soldered on that board, but the control circuitry is (duals
etc. which are needed also elsewhere).

Dimiter
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