[time-nuts] TAPR TICC boxed (input protection)
davidwhess at gmail.com
Sun Apr 9 14:00:54 EDT 2017
On Sat, 8 Apr 2017 21:43:31 +0200, you wrote:
>Am 08.04.2017 um 17:52 schrieb David:
>> If they are not being tested, then where is the maximum specified
>> leakage number coming from? For a small signal bipolar transistor it
>> will typically be 25nA, 50nA, or 100nA, but the InterFET datasheet (1)
>> shows 10pA maximum and 1pA maximum for the A versions.
>The large print giveth and the small print taketh away.
>Usually there are footnotes and weasel words like "sample tested",
>"by characterisation" or "not production tested".
>The time such a small device sits on the wafer tester costs much more
>than the silicon. For 100 msec.
>At 1 pA it takes an eternity until the capacitances in the setup
>are charged. Just the waiting time makes such a diode or FET
>a premium part.
Low leakage is the defining characteristic of these JFETs so they
better be testing them.
The Calogic datasheet was the only one I checked which said anything
like "For design reference only, not 100% tested" and it did not apply
to the leakage current.
The non-A parts are only tested down to 10pA.
>Back to input protection:
>Someone in the sci.electronics.design group mentioned these
>< https://www.digikey.de/products/de?keywords=cmpd6001s >
>but, as usual, typical values, and watch the plot with the temperature
>as parameter. At least they are cheap.
I think these were pointed out to me before. Since I would have to
test them to guaranty leakage below 500pA, I might as well test a
cheap small signal transistor.
If you want a laugh, take a look at NXP's various "low leakage
diodes"; they only specify and test them down to nanoamps. But I
assume for most new EEs that *is* low leakage.
>Also interesting, while not exactly low leakage diodes, are these
>USB3 lightning arrestors:
>< https://www.digikey.de/products/de?keywords=296-25509-1-nd >
>Looks like they don't spoil the timing.
USB is not leakage sensitive. It looks like these were only tested to
the same 100nA standard as many transistors which makes sense; they
just need to weed out bad parts.
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