High dielectric constan caps, some weirdness

I read that as R > 1000 ohm farads/0.000022 farads = 45.4 megohms. IOW they guarantee that the self-discharge time constant is greater than

Blech. X7R should be more like -10% at rated voltage.

Cheers

Phil Hobbs

Hmm, interesting, Foxit reader shows a dot instead of a slash.

That's why this graph surprised me. I've sent an inquiry but not sure whether it gets answered in due time and I am not related to the emporor or any of that :-)

Sure it's not 1000/C in Farads? That would be about 50 megs.

I don't think you'll have any problems in 40 seconds.

Do you have room for something like a polymer aluminum cap?

=A0IOW

X7R capacitance does not fall off 65% @ 5V regardless of rated voltage. Someone slipped in the wrong graph, a 6.3V Z5U or some such.

James

An ohm-farad is the same as a second. They're specifying the self-discharge time constant.

Cheers

Phil Hobbs

Potato - Potatoe!~

Still 50 megs. Well, 45.45...

Thanks Dr. Hobbs.

Ok, but in a datasheet that is not supposed to happen.

I don't think so either. But it would be nice to know to be able to put some rationale about this function into the module spec. It's kind of an unusual circuit that keeps doing some stuff while there no longer is any power available.

Not really. I've got almost 250 mils of height to work with but it's a high-temp environment. Ideally we don't want to have any electrolytics, and most definitely not tantalum. Normally an X7R cap should do this nicely but I can't put one in there when the datasheet says otherwise, even in case the information in there should be wrong.

What irks me is the fact that Digikey and others are starting to have bland links, instead of a datasheet all you get is meaningless sutff like photos. I shouldn't have to scour the web for the datasheet.

Well, I was also going to suggest a polymer tantalum, but I don't dare mention it now.

Doesn't matter, since Digikey hardly stocks any of the stuff they list.

Well, it isn't QUITE that bad, yet, but a hell of a lot of stuff is getting hard to find. It isn't only Digi-Key and others not stocking items, also the manufacturers are stopping production of a wide range of parts. Panasonic has canned whole lines of parts (transistors, regulators, diodes, etc.)

Jon

This is typical: do a parts search on the Digikey site and get, say,

Mouser is about as bad lately. What's the point of listing parts that aren't stocked and apparently can't be ordered?

Just because they're not stocked, doesn't mean the parts can't be ordered. I don't know why you'd order non-stocked parts from DigiKey, but it can be done.

Ok, so why buy anything if you simply can't have it same-day? "Non stocked" just means you can't get it instantly. It then becomes the same purchase as a purchase from literally anyone else on Earth: submit a quote with price and ETA, decide if you want it or not, then sit and wait.

Indeed, Digikey is even better than the usual process, because they specify price on almost all "non stocked" items, and you can usually establish a rough ETA by adding to your cart and seeing what it says.

My one "non stock" story, I ordered a Vishay/IR diode which was out of stock; ETA was something like 6 weeks, actually took something like 8 or 10, give or take a call about it. Without a deadline on that particular project, I was fine waiting.

At work, every day, we buy transformers and capacitors that physically don't exist before they are ordered. But they arrive as scheduled. Why should I be afraid that something doesn't physically exist before buying it?*

Tim

or

Hmm, that's true. Maybe an alien life-form from Earth's future slipped it in there, as some sort of cryptic message/warning.

What's the stock market been doing? ;-)

--James

Yesterday they actually confirmed that the graph is correct (!). So, I went with another manufacturer, I don't have much time left to dwell on such things for this design project.

Slid down 63 points yesterday but I stay out of it for the most part right now. Until I know what shakes out in Europe and (hopefully soon) get a feel on how the elections will go.

Right. I won't buy anything from DigiKey that I can't have immediately. Instant delivery is the only reason I'd ever buy from DigiKey. Like many here, I do use DigiKey as a gauge of availability.

If you like spending too much of your boss' money, sure. ;-)

Because the only reason I buy from DigiKey, in the first place, is because I need it *now*. If I can wait, I don't need DigiKey.

Everyone's needs are different, but if an item isn't stocked at DigiKey, the chances are good that it's never stocked anywhere. Custom parts are a whole different kettle.

D/1979255

I can tell you right up front that the ceramics are too leaky for that. Maybe polymer tantalums will work. Otherwise,you need the space for polymer caps.

Test if you don't believe me. I so would like to have current test data.

?-)

"high

charge

resistance

some

IOW

are

emporor

That is such a 1970s attitude. According to some, passe by 1990s. YMMV

?-(