What is X7R and X5R of ceramic capacitor? - Page 1
Forum section: electronics / beginners

author: javad2040
author_rank: Contributor
timestamp: August 17, 2017, 09:08:40 am
content: hi.I design a pcb for Xilinx Spartan 6 FPGA and i used lm1064 for produce 3.3v for FPGA. for getting this voltage i need to use 100nf ceramic capacitor in input.by searching in the capacitor schematic, i found X7R and X5R features of capacitor. what is X7R and X5R and why they are important?

author: nugglix
author_rank: Regular Contributor
timestamp: August 17, 2017, 09:18:37 am
content: See:

author: Rerouter
author_rank: Super Contributor
timestamp: August 17, 2017, 09:41:41 am
content: X7R and X5R are dielectrics of ceramic capacitors, these dielectrics describe the limit of tolerances over temperature span,In both cases to see if suitable requires looking at the datasheet, as there are other parameters like voltage de-rating, e.g. the effective capacitance value is lower when the supply voltage is higher. this changes even between voltage ratings of the same series of caps, and sometimes a 5V cap is better than a 25V, as the higher voltage in the same package meant the derating curve was sacrificed to meet the spec.

author: Benta
author_rank: Super Contributor
timestamp: August 17, 2017, 12:13:29 pm
content: X7R and X5R are the lowest grade of ceramic caps, but with the highest capacitance/volume ratio. If these grades are specified, it basically means you use almost anything. They are mostly used for supply decoupling purposes.

author: chris_leyson
author_rank: Super Contributor
timestamp: August 17, 2017, 01:16:34 pm
content: X7R are rated to 125C whereas X5R is only rated to 85C. The R suffix tells you that the capacitance change over temperature is +/- 15%. There is also a capacitance change with applied DC voltage, capacitance drops with an increase in applied DC voltage and X7R performs slightly better than X5R. Dielectrics to be avoided are things like Y5V as the capacitance will drop to only 15% or 20% of the rated value at max rated temp of 85C. Capacitance drop with increased apllied voltage is very dependant on package size with larger packages performing much better than the smaller 0603 or 0805 packages. There's a good app note from Maxim explaining some of the issues,https://www.maximintegrated.com/en/app-notes/index.mvp/id/5527as well as some good app notes from Murata and TDK. If capacitance change with temperature or applied voltage is an important part of the design then read the manufacturers data sheet.

author: djnz
author_rank: Regular Contributor
timestamp: August 18, 2017, 11:28:47 am
content: TheWikipedia article on 'Ceramic Capacitor'is quite informative.

author: w2aew
author_rank: Super Contributor
timestamp: August 18, 2017, 05:21:10 pm
content: Quote from: Benta on August 17, 2017, 12:13:29 pmNot really - the X7R really aren't too bad, X5R are a little worse (lower high temp limit). Each of these is a Class 2 dielectric, not as good as Class 1. The "lowest grade" ceramic caps are most commonly the Y5V and Z5U types. See the tables (above) for the 'decoder' for these ceramic types.

author: metrologist
author_rank: Super Contributor
timestamp: August 18, 2017, 05:50:37 pm
content: that second video's title frame, capacitor far left. I have a couple drawer of those...

author: mengfei
author_rank: Regular Contributor
timestamp: July 18, 2024, 06:43:45 am
content: Cool!Top line in search of "What is X7R and X5R of ceramic capacitor?"

author: Infraviolet
author_rank: Super Contributor
timestamp: July 18, 2024, 03:41:48 pm
content: "sometimes a 5V cap is better than a 25V"Just to get a sense for this, how vulnerable are ceramic caps to over-voltage conditions? If you're after an SMD ceramic towards the high end of capacitances, 22uF or 47uF say, you have a really hard time finding one rated for >16V. Is a 16V one always good enough for a 12V circuit (with some chance of brief higher spiking), or should one be using a 25V rated cap? Do ceramic caps die in a serious and permanent fashion from brief over-voltage events, by a few volts or a 10% or 20%, or just misbehave for the duration of the spike?Thanks

author: TimFox
author_rank: Super Contributor
timestamp: July 18, 2024, 04:06:28 pm
content: The "best" dielectric for ceramic capacitors is C0G/NP0, which is a Class-I dielectric with close to zero temperature co-efficient.Class-I dielectrics have lower dielectric constants than the Class-II ceramics, which can be "ferroelectric" with hysteresis and non-linear voltage dependence.Since the Class-II dielectric constants are much higher than C0G, they can be made with much higher nominal capacitance in a given physical size.In general, C0G smt capacitors are available up to 100 nF in reasonable sizes, while X7R and X5R can achieve multiple microfarads in similar sizes, for applications that can tolerate higher dielectric loss, dielectric absorption/hysteresis, and voltage co-efficient.In the past, the "Y" dielectrics were often used in disc ceramic capacitors, since they had only a single layer of dielectric between the electrodes, for a reasonable size disc package.If you must use "Y" or "Z" in modern MLCC multi-layer parts, read the datasheet carefully to see if the reduced capacitance at DC voltage is acceptable: the voltage rating for these parts only tells you how much voltage the part can safely withstand, not necessarily the recommended operating voltage.

author: Vovk_Z
author_rank: Super Contributor
timestamp: July 18, 2024, 10:03:41 pm
content: Quote from: mengfei on July 18, 2024, 06:43:45 amI didn't understan a sence of this question too, because I guess the very first line of Google search gives an answer.It's like question "How mane mm2 in AWG" etc.

author: wraper
author_rank: Unknown
timestamp: July 18, 2024, 10:47:06 pm
content: Then learn about voltage-dependent capacitance and ageing (typically glossed over if mentioned at all in datasheets) and temperature instability specified by X7R/X5R type will look like small potatoes.