Ceramic cap hoarding

Not guilty, your honour. To be clear, I *do* hoard loads of ceramics, but none of them are remotely that large. ;-)

Digikey seems to have a few K in stock.

Is the value critical? There are lots of others from 0.68 to 1.5 uF in stock at Mouser.

Digikey seems to have a few K in stock.

Is the value critical? There are lots of others from 0.68 to 1.5 uF in stock at Mouser.

I had this problem a few weeks ago with a couple of ceramic caps. We found stock to get our run going, but I started checking around in case we ran i nto this again. Seems there are a number of values around 1 uF that are mu ch less in demand and so would do the job if you aren't worried about too m uch capacitance, which nearly no one using ceramic devices are. I'm not su re I was looking for an X7R device, might have been an X5R part, but the sa me should hold for X7R.

I was told back in January that ceramic caps were going on allocation. I d on't know how much hording is going on exactly, but I bet a *lot* of the ba ck ordering is future hording. I recall a report of an exercise in a colle ge class where a supply chain was set up. The first guy gave orders to the next, and this guy decided what to order from the next and so on with five or six layers. By the end of the exercise the orders to the last guy in t he chain were way up and down with wild oscillations. When the students as ked the first guy, he said the instructor had told him to order 100 each ti me. lol

I have some excess inventory. Maybe there is a profit opportunity.

Rick C.

Yes, MLCC caps are highly constrained right now. We have engineers redesigning boards around large MLCCs just to keep the plants open and customers supplied. Inductors aren't good, either. I'm told by suppliers that transistors and diodes are next.

AND don't care about the CV curve.

That's the issue. Murata and TDK actually publish C(V) curves, but everybody else AFAIK keeps them a deep dark secret.

Cheers

Phil Hobbs

or increase C_nominal by a factor of 10!

NT

I don't typically see much difference in the CV curve between X5R and X7R.

Rick C.

And KEMET, and Samsung (sometimes). Who does that leave? Taiyo Yuden does not. Venkel, if you're in high volume, I guess -- I haven't seen if they do or not.

Or if you're Joerg, none of these data "exist"...

Tim

I haven't seen Kemet or Samsung publish C(V) curves for individual part numbers. Do you have a link for either? It would be nice to have.

Cheers

Phil Hobbs

Used to be available as an executable only, now it's online. Murata too.

Samsung's website isn't much help, last I looked. Seems like a bit under half their datasheets randomly have characteristics. Digikey has several PDFs linked to a part, not just the you see in the search view. Click onto the part page.

Oh... and watch out for 404s, because they're dumb like that, too? Like this one would, except the Characteristics sheet is 404:

It looks like [working] char sheets are more common now, maybe they've been rolling them out ever so slowly?

Tim

IMHO, 0603 parts are going to see less usage over the next few years, and a lot of EOL notices. I don't think it's a coincidence that a lot of recent capacitor shortages involve 0603 parts.

Yes, the voltage ratings on 0603 caps are higher, but how often is that really an issue, even taking voltage coefficient into account? (Almost) nobody needs 50 volt 0603 caps.

Most data sheets I've seen lately come right out and tell you to use

-- john, KE5FX

Very nice, thanks!

Cheers

Phil hobbs

Maybe you don't, but since higher values drop by 80% or so at rated voltage, I use a lot of 50V caps on 12-15V rails.

Cheers

Phil Hobbs

I recently had to cross some parts and found that even a 50 volt MLCC has s ignificant capacitance drop at 12 volts. I want to say it was still below

Rick C.

You're a digital guy, so decoupling is about all you use caps for. Some of us have reasons to care about stuff like distortion and parametric effects due to C(V) problems. That's why film caps still exist.

Cheers

Phil Hobbs

In actual measurements, I've found that the stated value of a bypass capacitor is just about its least-important property. Once you're over

Some fun with a TDS 694C:

I know you can't ignore the voltage coefficient entirely -- and yes, those measurements were made at very low voltage -- but just for amusement's sake, try putting a 1 uF 16V part in your 15V circuit and measure its effect. It will probably have about 100 nF of usable capacitance... and I'll bet that makes absolutely no difference at all.

-- john, KE5FX

Is bypassing the only thing you use caps for? I'm an actual circuit designer. ;)

Cheers

Phil Hobbs