Passive Components Blog
No Result
View All Result
  • Home
  • NewsFilter
    • All
    • Aerospace & Defence
    • Antenna
    • Applications
    • Automotive
    • Capacitors
    • Circuit Protection Devices
    • electro-mechanical news
    • Filters
    • Fuses
    • Inductors
    • Industrial
    • Integrated Passives
    • inter-connect news
    • Market & Supply Chain
    • Market Insights
    • Medical
    • Modelling and Simulation
    • New Materials & Supply
    • New Technologies
    • Non-linear Passives
    • Oscillators
    • Passive Sensors News
    • Resistors
    • RF & Microwave
    • Telecommunication
    • Weekly Digest

    5th PCNS Awards Outstanding Passive Component Papers

    TDK Releases Ultra-small PFC Capacitors

    KYOCERA AVX Releases Novel Mini BME Stacked Ceramic Capacitors

    Vishay Releases Class 1 Leaded High Voltage Ceramic Disc Capacitors

    TDK Releases 140C Compact Vibration Robust Automotive Aluminum Capacitors

    DigiKey Presents Factory Tomorrow Season 5 Video Series

    Samsung MLCCs Lineup for In-Vehicle Infotainment

    source: Samtec

    Best Practices for Cable Management in High-Speed and High-Density Systems

    Würth Elektronik Unveils Compact Common-Mode Data Lines Chokes

    Trending Tags

    • Ripple Current
    • RF
    • Leakage Current
    • Tantalum vs Ceramic
    • Snubber
    • Low ESR
    • Feedthrough
    • Derating
    • Dielectric Constant
    • New Products
    • Market Reports
  • VideoFilter
    • All
    • Antenna videos
    • Capacitor videos
    • Circuit Protection Video
    • Filter videos
    • Fuse videos
    • Inductor videos
    • Inter-Connect Video
    • Non-linear passives videos
    • Oscillator videos
    • Passive sensors videos
    • Resistor videos

    Ripple Steering in Coupled Inductors: SEPIC Case

    SEPIC Converter with Coupled and Uncoupled Inductors

    Coupled Inductors in SEPIC versus Flyback Converters

    Non-Linear MLCC Class II Capacitor Measurements Challenges

    Percolation Phenomenon and Reliability of Molded Power Inductors in DC/DC converters

    Root Causes and Effects of DC Bias and AC in Ceramic Capacitors

    How to Calculate the Output Capacitor for a Switching Power Supply

    Switched Capacitor Converter Explained

    Understanding Inductor Dot Markings and Their Application in LTspice

    Trending Tags

    • Capacitors explained
    • Inductors explained
    • Resistors explained
    • Filters explained
    • Application Video Guidelines
    • EMC
    • New Products
    • Ripple Current
    • Simulation
    • Tantalum vs Ceramic
  • Knowledge Blog
  • Suppliers
    • Who is Who
  • Events
  • Home
  • NewsFilter
    • All
    • Aerospace & Defence
    • Antenna
    • Applications
    • Automotive
    • Capacitors
    • Circuit Protection Devices
    • electro-mechanical news
    • Filters
    • Fuses
    • Inductors
    • Industrial
    • Integrated Passives
    • inter-connect news
    • Market & Supply Chain
    • Market Insights
    • Medical
    • Modelling and Simulation
    • New Materials & Supply
    • New Technologies
    • Non-linear Passives
    • Oscillators
    • Passive Sensors News
    • Resistors
    • RF & Microwave
    • Telecommunication
    • Weekly Digest

    5th PCNS Awards Outstanding Passive Component Papers

    TDK Releases Ultra-small PFC Capacitors

    KYOCERA AVX Releases Novel Mini BME Stacked Ceramic Capacitors

    Vishay Releases Class 1 Leaded High Voltage Ceramic Disc Capacitors

    TDK Releases 140C Compact Vibration Robust Automotive Aluminum Capacitors

    DigiKey Presents Factory Tomorrow Season 5 Video Series

    Samsung MLCCs Lineup for In-Vehicle Infotainment

    source: Samtec

    Best Practices for Cable Management in High-Speed and High-Density Systems

    Würth Elektronik Unveils Compact Common-Mode Data Lines Chokes

    Trending Tags

    • Ripple Current
    • RF
    • Leakage Current
    • Tantalum vs Ceramic
    • Snubber
    • Low ESR
    • Feedthrough
    • Derating
    • Dielectric Constant
    • New Products
    • Market Reports
  • VideoFilter
    • All
    • Antenna videos
    • Capacitor videos
    • Circuit Protection Video
    • Filter videos
    • Fuse videos
    • Inductor videos
    • Inter-Connect Video
    • Non-linear passives videos
    • Oscillator videos
    • Passive sensors videos
    • Resistor videos

    Ripple Steering in Coupled Inductors: SEPIC Case

    SEPIC Converter with Coupled and Uncoupled Inductors

    Coupled Inductors in SEPIC versus Flyback Converters

    Non-Linear MLCC Class II Capacitor Measurements Challenges

    Percolation Phenomenon and Reliability of Molded Power Inductors in DC/DC converters

    Root Causes and Effects of DC Bias and AC in Ceramic Capacitors

    How to Calculate the Output Capacitor for a Switching Power Supply

    Switched Capacitor Converter Explained

    Understanding Inductor Dot Markings and Their Application in LTspice

    Trending Tags

    • Capacitors explained
    • Inductors explained
    • Resistors explained
    • Filters explained
    • Application Video Guidelines
    • EMC
    • New Products
    • Ripple Current
    • Simulation
    • Tantalum vs Ceramic
  • Knowledge Blog
  • Suppliers
    • Who is Who
  • Events
No Result
View All Result
Passive Components Blog
No Result
View All Result

Capacitor Coupling for Minimum Impedance

30.3.2022
Reading Time: 4 mins read
A A

source: signal integrity journal article

January 2, 2018, Anto Davis and Steve Sandler. A negative coupling coefficient to optimize capacitor placement may not always lead to lower impedance.
It is well known that the mounting loop of a capacitor owns the major share in parasitic inductance [1]. A practical capacitor when mounted in a printed circuit board has parasitic inductance (L) associated with it. Its equivalent circuit is a series RLC circuit where R represents the loss associated with the capacitor (C). It has a self (series) resonant frequency given byabove which it acts as an inductance. Other important contributors to the parasitic inductance are ESL and plane spreading inductance.

RelatedPosts

Rohde & Schwarz Introduces New Family of High Performance LCR Meters

Supercapacitor Balancing Methods Comparison

A mounting loop is formed by the two vias connecting a capacitor to the power-ground planes. A small form factor capacitor reduces this area and helps to minimize the parasitic inductance. Closer power-ground planes reduce the plane spreading inductance.

Geometry for Negative Coupling Coefficient

With two capacitors in parallel, we can generate a negative coupling coefficient to reduce the parasitic inductance. This is shown in Figure 1. Points A and E are on the same plane and points B and F are on the same plane. Assume that the planes are power and ground separated by thin dielectric of thickness (2-3 mils).

Figure 1(b) shows the geometrical connection for negative coupling coefficient (M and k are negative). When power and ground planes are present, this geometry can be achieved by changing via locations; B and E are on the same plane and A and F are on the same plane.

Figure 2 shows the equivalent circuit diagram of two capacitors in parallel. Writing equations for it,

1. Identical Capacitors

For large values of w, the Eq. 2 becomes the classic equation of coupled parallel inductors.

where + and – signs indicate positive and negative couplings. For equal loop areas (L1 = L2 = L), inductance is given by,

Experiments are conducted with two ceramic disc type capacitors of values C1 = C2 = 4.7 nF. Measurement with a capacitor meter gives their values as 4.30 nF. The leads are cut and made with insulated copper wire of SWG 21 (diameter = 0.813 mm). Leads make a loop of area 1.5 cm _ 0.5 cm. The measurement device is Rohde & Schwarz vector network analyzer (VNA). The scattering parameters measured are converted to impedance values. VNA is set with the following values: Resolution band width (RBW) = 10 Hz; number of points = 1000; and power = -15 dBm. Two loops are kept at a distance of 1 mm (edge to edge). The coupling coefficient between the loops (k = M/L) is calculated to be 0.4 where L is 17.6 nH and M is 6.97 nH [2]. Simulation and experimental results are shown in Fig. 4(a) and Fig. 4(b) respectively. At 100 MHz, inductance is 2.5 times (8 dB) lesser than that for positive coupling case.

No surprises until here. How about the case where the two capacitor values are different?

Non-identical Capacitors

When the capacitor values are different, the parallel combination produces antiresonance peaks as shown in Figure 5. The anti-resonance peak is lower for the positively coupled case. It is assumed that the capacitors have nearly equal mounting inductance, and their sizes are comparable. Experiments are conducted for the same values of the previous experiment, except that one capacitor is changed to 390 pF. A measurement with capacitance meter gives 380 pF for this capacitor. Experimental results (Figure 5(b)) shows that the antiresonance peak is lower for positively coupled case by 3.2 times. When both the capacitors become inductive, the equivalent inductance is lower for negative coupling case.

Summary

A negative coupling coefficient produces a larger anti-resonant peak compared to a positive coupling coefficient, even though the equivalent inductance is lower. Multiple anti-resonant peaks are capable of generating rogue waves [7, 8], and suppressing them are becoming more and more important. For low noise circuits, power distribution network (PDN) resonance is an important design issue, and should be suppressed!

How about the tolerance of two identical ceramic capacitors connected in parallel? `It depends’ on the type of capacitors that determines the capacitance variations. Plotting eq. (2) with worst-case values will give the answer. Authors leave this to the curious reader to explore!

A. K. Davis (ECE, GeorgiaTech, Atlanta, USA) & S. M. Sandler (Picotest, Phoenix, AZ 85085, USA)

2. References

[1] Roy, T., Smith, L., and Prymak, J.: `ESR and ESL of ceramic capacitor applied to decoupling applications’, IEEE 7th Top. Meet. Elect. Perform. Electron. Packag., 1998, pp. 213-216.

[2] Paul, C. R.: `Effectiveness of multiple decoupling capacitors’, IEEE Trans. Electromagn. Compat., 1992, 34, (2), pp. 130-133.

[3] Davis, A.K.: `Effect of magnetic coupling between the mounting loops of two parallel capacitors on antiresonance’, IET Sci. Meas. Tech., 2016, 10, (8), pp. 889-899.

[4] Davis, A.K., and Gunasekaran, M.K.: `Microprocessor-conducted noise reduction with switched supercapacitors’, Electron. Letters, 2014, 51, (1), pp. 92-94.

[5] Novak, I., Pannala, S., and Miller, J. R.: `Overview of some options to create low-Q controlled-ESR bypass capacitors’, IEEE 13th Top. Meet. Elect. Perform. Electron. Packag., 2004, pp. 55-58.

[6] Davis, A.K.: `Effect of a magnetically coupled resistive loop on antiresonance’, Electron. Letters, 2016, 52, (13), pp. 1162 – 1164.

[7] Steve Sandler: `Target impedance based solutions for PDN may not provide realis-tic assessment’, available https://www.edn.com/design/test-and-measurement/4413192/Target-impedance-based-solutions-for-PDN-may-not-provide-a-realistic-assessment

[8] Eric Bogatin, Istvan Novak, Steve Sandler, Larry Smith, Brad Brim, and Steve Weir: `Target Impedance and Rogue Waves’, available http://www.electrical-integrity.com/Paper_download_files/DC16_TargetImpedanceRogueWaves-panel.pdf

 

 

Related

Recent Posts

5th PCNS Awards Outstanding Passive Component Papers

14.9.2025
5

TDK Releases Ultra-small PFC Capacitors

10.9.2025
22

KYOCERA AVX Releases Novel Mini BME Stacked Ceramic Capacitors

10.9.2025
20

Vishay Releases Class 1 Leaded High Voltage Ceramic Disc Capacitors

10.9.2025
11

TDK Releases 140C Compact Vibration Robust Automotive Aluminum Capacitors

5.9.2025
28

Samsung MLCCs Lineup for In-Vehicle Infotainment

4.9.2025
31

Vishay Releases Harsh Environment Robust DC-Link Film Capacitor

2.9.2025
38

Influence of Tantalum Capacitor Pellets Size on Stability During Oxide Film Formation

29.8.2025
43

Modelithics Release Discrete Components Optimization Article for RF/Microwave Designers

28.8.2025
15

Samsung Extends Capacitance of MLCC 0805 X7T 250V to 100nF

28.8.2025
34

Upcoming Events

Sep 16
17:00 - 18:00 CEST

EMI Shielding Challenges

Sep 22
September 22 @ 13:00 - September 25 @ 15:15 EDT

Pre Cap Visual Inspection per Mil-Std-883 (TM 2017)

Sep 30
September 30 @ 12:00 - October 2 @ 14:00 EDT

MIL-Std-883 TM 2010

Oct 17
12:00 - 14:00 EDT

External Visual Inspection per MIL-STD-883 TM 2009

Oct 20
October 20 - October 23

Digital WE Days 2025 – Virtual Conference

View Calendar

Popular Posts

  • Buck Converter Design and Calculation

    0 shares
    Share 0 Tweet 0
  • Boost Converter Design and Calculation

    0 shares
    Share 0 Tweet 0
  • Flyback Converter Design and Calculation

    0 shares
    Share 0 Tweet 0
  • LLC Resonant Converter Design and Calculation

    0 shares
    Share 0 Tweet 0
  • Dual Active Bridge (DAB) Topology Explained

    0 shares
    Share 0 Tweet 0
  • Ripple Current and its Effects on the Performance of Capacitors

    3 shares
    Share 3 Tweet 0
  • What is a Dielectric Constant and DF of Plastic Materials?

    4 shares
    Share 4 Tweet 0
  • SEPIC Converter Design and Calculation

    0 shares
    Share 0 Tweet 0
  • How to Design an Inductor

    0 shares
    Share 0 Tweet 0
  • Core Materials, Permeability and Their Losses

    0 shares
    Share 0 Tweet 0

Newsletter Subscription

 

Passive Components Blog

© EPCI - Leading Passive Components Educational and Information Site

  • Home
  • Privacy Policy
  • EPCI Membership & Advertisement
  • About

No Result
View All Result
  • Home
  • Knowledge Blog
  • Premium Suppliers

© EPCI - Leading Passive Components Educational and Information Site

This website uses cookies. By continuing to use this website you are giving consent to cookies being used. Visit our Privacy and Cookie Policy.
Go to mobile version