X5R vs X7R MLCC

X7R is usually all upside. They are also better at higher temperatures if that's ever a concern.

I don't need a Tesla, unless they build mountain bikes :-)

I think someone asked Elon about "scooters" once and he seemed to feel that was "beneath" the image of Tesla while motorcycles and everything large is not. Basically the company is an extension of his ego.

But obviously any type of bike they come up with would be battery powered which defeats the whole point of the mountain bike thing.

Doesn't mean you don't know anyone interested... I'm just sayin'...

Rick C.

Tesla referral code -++-

and I want to place an order to support production for a while. In perfor ming a Digikey/Mouser search I see there are now X7R devices in the same fo otprint. I know the X7R will be more stable under DC voltage which is an a dvantage *if* there is much DC on the input. The amplifier circuit has a 6 volt DC bias on the input (half way to the +12 volt rail). The caps preve nt the input from seeing this bias. The design passes all functional tests in production (including frequency response) with the X5R devices.

are only four devices on the board, so a small increase in price is not so significant. I'm just wondering if there is any technical downside to usin g the X7R formulation in place of the X5R. Or is the X7R formulation all u pside relative to the X5R?

Not sure, with some caps the manufacturer is more important than the number. I've never had any problems with ceramics. We use a lot of x7r 0.1 uF.

George H.

It's actually quite a market for mountain biker. I know several who have crossed over to the dark side for mostly medical reasons. One bought a German E-bike, the other built it by himself.

up and I want to place an order to support production for a while. In perf orming a Digikey/Mouser search I see there are now X7R devices in the same footprint. I know the X7R will be more stable under DC voltage which is an advantage *if* there is much DC on the input. The amplifier circuit has a 6 volt DC bias on the input (half way to the +12 volt rail). The caps pre vent the input from seeing this bias. The design passes all functional tes ts in production (including frequency response) with the X5R devices.

e are only four devices on the board, so a small increase in price is not s o significant. I'm just wondering if there is any technical downside to us ing the X7R formulation in place of the X5R. Or is the X7R formulation all upside relative to the X5R?

Yeah, the generic 0.1 uF decoupling caps are already X7R. Much of this boa rd was so tight I would use X5R where I had to so they would fit an 0603 fo otprint or in this particular case a 1210 footprint (22 uF, 25V). The same part in X7R would have been the next size up.

I seem to recall having selected a wrong part that was discovered about a y ear later, too low a voltage. Even in just that year the density had impro ved enough so I found a part that was rated to the higher voltage in the sa me footprint.

I think I will buy some reels of X5R parts because of the price, but I will consider X7R if X5R becomes unobtainium.

Rick C.

Tesla referral code ++++

Apples to apples, X7R is better, for sure. However, high-density MLCCs are all over the map in performance depending on both manufacturer and part number. You really have to find the characteristic curves to know.

We've all been feeling the MLCC shortage this year, so I put up a blog post with links to a bunch of makers' characteristic curves.

Samsung has decent characteristic curves published on Digikey. (Note that it's the characteristics link and not the datasheet link that you want. Cute eh?)

Cheers

Phil Hobbs

Grin.. W. Allen, "The food stinks", "Yeah, and the portions are small." GH

I was just informed 2 days ago that my Digi-Key order of Samsung caps is on back order :-(

Going to run a production batch with untested no-namers...wish me luck!

I'd test them first. It's not that hard--put two in series and bias the middle.

Cheers

Phil Hobbs

I thought I invented that!

(Actually, I did.)

John Larkin wrote

Terrible. Better use tantalum? What am I missing here?

Huh, what did you measure? Did you very the frequency till you found the point where C/2 = 50 ohms? ... splitting the voltage between C's and FG 50 ohm source.

George H.

Checking for what, even voltage? Then check with a capacitance meter???

Rick C.

Tesla referral code +-+-+

No, you put a large resistor across the ends so there's no DC on the meter, ground one end, bias the middle via another large resistor, and put a C meter across the ends. No muss, no fuss.

Cheers

Phil Hobbs

Right, I tweaked the frequency to find the -3 dB point, with the 50 ohm generator. Of course, that measures C/2. Both caps see the same DC voltage.

I feel better doing this than trusting some digital display. As I turn the frequency knob, I can see the smooth change of voltage vs frequency and be confident everything is OK. Maybe see the ESL and ESR at higher frequencies.

It's fun to drive one of these nonlinear caps with a big square wave too.

There's nothing missing here. I just measured a cap.

That 4.7u is fine to filter the output of a 1.2 or 3.3 volt switcher, or for AC coupling. Or use the 47u 6.3v version, which has an even worse cv curve.

Tantalums have a lot of ESR, which is sometimes good, sometimes bad. They are always big and expensive.

John Larkin wrote

Yes, OK tantalums are more expensive, I use those all the time for linear regulator decoupling. Again, do not save on parts... I could not see me use a capacitor for AC coupling between stages if its value could be 10x out of specified range.

Makes me wonder too how microphonic those caps are? With microphonic I mean creating voltages when vibrating?

I sort of like to tap on boards with a pen... to find dry joints etc.. Was no there a tread about it here years ago? And the reverse, making sound when AC is applied.

But then I am biased, I like tantalums, never had a problem with those.. except when put in the wrong way around...

Hey, I assume COG/NPO caps don't have any voltage coef. (I use those for AC coupling, signal filters.)

You have to picky about manufacturers, someone saved a few cents on cheaper tants, and the 35V ones failed at 15-20V... semi my mistake as I used them on a 24V supply line. (older design... in the past I don't think tant's were so flaky.)

George H.

George Herold wrote

Assuming is a dangerous thing... but poly based caps should be OK, use those in my LC meter. I will measure some of those ceramic caps when I get around to it.