[SI-LIST] Re: controlled ESR capacitors or series resistors
- From: Romi Mayder <romi.mayder@xxxxxxxxxx>
- To: Anto Davis <antokdavis@xxxxxxxxx>, "istvan.novak@xxxxxxxxxxx" <istvan.novak@xxxxxxxxxxx>, "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Sun, 28 Dec 2014 02:03:16 +0000
Hi Anto,
I believe you will find the ESR tolerance (min and max) in the data sheet for
each specific capacitor.
Regarding your question related to inductance and capacitance values varying
with respect to frequency, you may find reading the following paper to be
helpful:
http://www.xilinx.com/support/documentation/white_papers/wp411_Sim_Power_Integrity.pdf
In this paper, the authors teach a method of cascading S-parameter models to
simulate the self impedance of power distribution networks. Individual
S-parameter models are used for each capacitor.
Touchstone V1.0 file format works well for PI simulations. For combined SI and
PI simulations, using Touchstone V2.0 file format results in more accurate
simulation results.
For more information related to using Touchstone V2.0 file format for SI/PI
simulations, you may find reading the following paper to be helpful:
http://www.xilinx.com/events/designcon2014/11_WE5Paper_Touchstonev2SIPISParameterModels_v2.pdf
I hope this helps answer your questions.
Kind Regards
Romi
From: Anto Davis [mailto:antokdavis@xxxxxxxxx]
Sent: Friday, December 26, 2014 11:38 PM
To: Romi Mayder
Cc: istvan.novak@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: controlled ESR capacitors or series resistors
Thanks Romi Mayder,
That was a helpful information.
It has ESR from 0.1 to 1 ohms.
The critical or over damping should be chosen for the design. If, plane
spreading L is neglected, if the mounting inductance is the main culprit. ESR^2
> L/C, so it is also a function of Capacitance also, more clearly,
capacitance/volume. So if I can get higher C value per volume, that has better
chance of giving critical/over damped condition. The L < 0.01C for 0.1 ESR, So,
1 uF can have L of 10 nH and 0.1 uF can have 1 nH.
If the design is for lower voltage (less than 1 V), C/volume can be higher,
since the dielectric breakdown voltage can be lower. So the voltage is another
design choice.
In actual practice ESR varies with temperature and frequency, so the minimum
should be taken for the design.
I guess, the Murata specify the minium promising ESR, right?
Thanks,
Anto
On Sat, Dec 27, 2014 at 5:40 AM, Romi Mayder <romi.mayder@xxxxxxxxxx> wrote:
Hi Anto,
You may also find it helpful to check out the "LLR" series of controlled ESR
capacitors from Murata. Murata "LLR" series caps offer several different ESR
values for the same/similar capacitance value in the same size package with
nearly same inductance. You can get up to 1000mOhm of ESR if you want/need it.
Kind Regards
Romi
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Istvan Novak
Sent: Saturday, December 20, 2014 10:28 AM
To: antokdavis@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: controlled ESR capacitors or series resistors
Anto,
You know the answer :-) : it depends.
Once you are through the design process and figured out what ESR for each piece
you want, you need to consider the required bandwidth of the part. If you add
resistance with a separate part, it will increase the inductance of the
structure, limiting its bandwidth. Usually if you need hundreds of milliohms
or higher, separate discrete parts tend to be OK or better, for low milliohm
values it is better to use a single-piece solution.
Regards,
Istvan Novak
Oracle
On 12/19/2014 11:52 PM, Anto Davis wrote:
> Hi,
> For optimum flat PDNs, the series resistor should be equal to square
> root (L/C).
> Out of the two options (1: controlled ESR caps 2: adding series
> resistors to capacitors) which is more commonly chosen?
> Is there any other option available ?
>
> Thanks,
> Anto
>
>
>
>
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