Win, where do they all come from ? (e-)

ADG1211.

Sorry, I didn't see the fC vs pC units. That's amazing. Would you be kind enough to measure the charge-injection vs common-mode switched voltage? As is often the case, the AD datasheet shows a strong switched-voltage dependency, rising to >0.2pC at 1.0V, >1pC at 5V with +/-5V supplies, and 3pC at 10V with +/-15V supplies.

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 Thanks,
    - Win

"qrk" a écrit dans le message de news: snipped-for-privacy@4ax.com...

Mark, they decided (Fairchild) they have to cancel my samples order and urge me to go through some distri.

As it seems I've found the right part, I'm afraid I won't look further into this direction. Should I have it I'd test it, but now...

Second time they do that. Stupid policy.

If you test it, let us know :-)

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Thanks,
Fred.

Just to clarify my question, the datasheet charge-injection plots commonly show a curve of changing charge-injection, going through zero at some point. The ADG1211's plots are in the low pC region, not the sub fC region. I'm wondering if you have found a special voltage, and what the charge-injection vs voltage plot is for the ADG1211 measured your way, with neither side of the switch tied to a low-Z input signal. You'll have to change the voltage on the capacitor or change both power-supply voltages together to do this test. Surely the result will be important for your application, besides being of interest to me and the others here?

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 Thanks,
    - Win

A bit OT, but following this interesting topic I did some search for FSA66 and found this:

This exact topic discussed here.

Looks like they're trying to make their forum appear well-visited by directly relying usenet posts from appropriate groups. Not sure I like this.

BTW, FSA66 looks like a very usable part for some RF front-end balanced mixer, possibly into the VHF region.

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Siol
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Rather than a heartless beep
Or a rude error message,
See these simple words: "File not found."

I didn't had much time to do this yesterday. To fully clarify things, there are 2 injected charges quanta, when switching. One on each switch side. More, the charges at opening and at closing are not necessarily equal, leaving a net charge on the node(s) after a complete on-off or off-on cycle. With the datasheet measurements conditions, we just see one side charge, the other side being shunted to ground by the source side generator and we just see the charge left at the switch opening transition. The net injected charge is unknown, as is the turn ON switching charge since it is dumped to groung through the switch channels.

As you've understood both charges are important to me, but not for the same reasons.

The hold charge (lets call it like this) is the one measured under the datasheet conditions (one side shorted to ground, the other side hooked to a

1nF cap). The voltage offset on the cap after the hold event measures the hold charge. The AD parts, ADG1211 as well as the ADG44x, make a nice job on this hold charge in the 500fC-1pC range depending on the part#. This charge is too high for my purpose, but it can easily be trimmed by adjusting one supply voltage, which is nothing else than setting the common mode voltage bias point where the charge perfectly cancels on the curves of the datasheet, as you have noted. In my test report ( ) the trimming sensitivity is about 1mV/fC of charge correction, which translates to about +14V/-15V supply voltages for the ADG444.

This hold charge is not a problem for me since it is trimmable and I have trimmed it down to the fC level (1uV step). This fC level is not the one I reported above as happy news.

Then comes the net injected charge (sum of both sides), which should sums over an ON/OFF cycle as exactly zero for a perfectly isolated switch (only capacitive coupling charge injection). That's where the ADG1211 makes a huge difference over the ADG444 (about 2E6 times better!).

I've done a complete set of measurements (both charges and DC leakage vs common mode). The set up was:

Fully ON or 1kHz | .---> SCOPE | AD8066 | V | _/ |\\ | ------o/ o-------+----+-------|+\\ | ___ | | | | >-+---|___|--+---> DVM | | | .-|-/ | | --- .-. --- | |/ | | --- 47n 100M | | --- 1n | | --- | | | | '------' --- | '-' | | | | | | === === === === GND GND GND GND

ADG1211_VS+

Indeed. Thanks for all that great data!

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 Thanks,
    - Win