Is a lower ESR always a better thing without qualification? That is to say, no thinking has to be done, just change the caps.We are changing some bulk decoupling caps to a part with 50% lower ESR. 150uF 16V tant. Doesn't this change the inrush current when turning on the device on empty caps?
ESR can be a good thing sometimes.
If your circuit has high inductance traces teh ESR can damp the resonant tank circuit and reduce ringing. Also ESR may be required by some switching regulators for stability.
So a sort answer, lower ESR is not ALWAYS better but it often is.
And in LDO regulators. Where they don't always tell you how critical the lower limit is because the marketeers might think that wouldn't look good.
Tantalums? I've had my fair share of kaboom experiences with them and its back to electrolytics here.
-- Regards, Joerg http://www.analogconsultants.com
I once got hit by a piece... It punched through my skin and had to be removed in a tiny surgery. Weird.
-- Johannes You can have it: Quick, Accurate, Inexpensive. Pick two.
What's the operating voltage?
Tantalums have a bad habit of detonating when used as supply bypasses. Inrush current heats up tiny asperites, then the tantalum becomes fuel and the MnO2 is the oxidizer. Boom. A change in vendor, plus lower esr, may introduce problems that you haven't seen before. Our rule is: no tantalums on supply rails.
Some voltage regulators, both linear and switchers, get unstable with low esr-loads.
John
Then you are Robocap, aren't you?
-- Thanks, Fred.
LOL That one was good!
Another one: My girlfriend read over a page of my books that i had left open on my desk. All over the day she was very silent and then during dinner she asled: "Why do you read all that stuff about Tantra-Capacitors? And that it brings a high capacity but is dangerous? What are you preparing for?"
I spent a whole night showing her what the difference between Tantal- and Tantra- was... Rather on the Tantal- side (to stay OT here) :-)
-- Johannes You can have it: Quick, Accurate, Inexpensive. Pick two.
Low ESR (and ESL) capacitors should be used whenever you need a fast surge or frequency response like in most low-voltage (3.3V and lower) circuits, for instance.
When using electrolytics, by the way, one should pay attention to load life and temperature ratings if you care about reliability and longevity.
Very strange - I use tantalums on almost 100% of my boards, and have only destroyed one. That happened when a 12V battery lead got shorted to the 3.3V supply regulated supply which had a tantalum on it. I think the tantalum was rated for about 6V. It just smoked and got a crack in it. A part next to it was more interesting, however. I can't remember the part number, but I had a TI CAN 3.3V transceiver in a SOIC-8 package nearby - and about half of the package blew out, leaving a gigantic hole in the chip. (and lots of magic smoke in my lab). That was exciting.
But anyways - under normal usage - I have never, ever had a tantalum explode, crack, or have any other problems.
-Mike
:-) Great luck there was not 'nuf dI/dt in that...
Had that with a BC548 once. It kept on glowing in the crater :-)
Don't try to use it in SMPS. Never ... ... ever.
-- Johannes You can have it: Quick, Accurate, Inexpensive. Pick two.
Thanks to all that replied. It turned out that the LDO would be unstable with a low ESR cap on its output. As a kind of manager, I really had to put the brakes on the "lower ESR is always better" idea....
My thoughts It must allways be best with low ESR . Remember that the ESR will disipate heat in the capacitor, and this heat is damaging the cap in short time.. If there is no heat ,then a electronic circuit can live forever. Heat is also a waist of power, and we always try to design to the lowest power-use. If a circuit will be unstable ,if the caps is changed with better caps, then the design is bad.. if resistors was needed ,then you put a resistor, and do not use the ESD resistor.
Alex in Denmark I'm new to this group, so I introduce myself here as an engineer working in the electronic field..( in most countries , think my degree would be like BSC ), I have 30 Y experience in repair of electronics, and 2Y experience with taking care of a electronic lab at university.. I live in Sonderborg Denmark..
With power supplies, the first and most difficult problem is to determine the characteristics of the load, i.e., the surge current or frequency response required. Once that's done, it's just a matter of going shopping for the correct regulator and then following the vendor's application notes in regard to what capacitors to use, and how many, to insure that the regulator is stable while at the same time providing a fast frequency response.
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