X2Y
®
F
ILTER
& D
ECOUPLING
C
APACITORS
The X2Y
®
Design - A Balanced, Low ESL, “Capacitor Circuit”
The X2Y
®
capacitor design starts with standard 2 terminal MLC capacitor’s opposing electrode sets, A & B, and adds a third electrode set (G) which surround
each A & B electrode. The result is a highly vesatile three node capacitive circuit containing two tightly matched, low inductance capacitors in a compact, four-
terminal SMT chip.
Signal 1
A
Ground
Signal 2
G1
B
G2
EMI Filtering:
The X2Y
®
component contains two shunt or “line-to-ground” Y capacitors. Ultra-low ESL (equivalent series
inductance) and tightly matched inductance of these capacitors provides unequaled high frequency Common-Mode
noise filtering with low noise mode conversion. X2Y
®
components reduce EMI emissions far better than unbalanced
discrete shunt capacitors or series inductive filters. Differential signal loss is determined by the cut off frequency of
the single line-to-ground (Y) capacitor value of an X2Y.
Power
A
G1
B
Ground
G2
Power Bypass / Decoupling
For Power Bypass applications, X2Ys
®
two “Y” capacitors are connected in parallel. This doubles the total
capacitance and reduces their mounted inductance by 80% or 1/5th the mounted inductance of similar sized MLC
capacitors enabling high-performance bypass networks with far fewer components and vias. Low ESL delivers
improved High Frequency performance into the GHz range.
GSM RFI Attenuation in Audio & Analog
GSM handsets transmit in the 850 and 1850 MHz bands using a TDMA pulse
rate of 217Hz. These signals cause the GSM buzz heard in a wide range of
audio products from headphones to concert hall PA systems or “silent” signal
errors created in medical, industrial process control, and security applications.
Testing was conducted where an 840MHz GSM handset signal was delivered
to the inputs of three different amplifier test circuit configurations shown below
whose outputs were measured on a HF spectrum analyzer.
1) No input filter, 2 discrete MLC 100nF power bypass caps.
2) 2 discrete MLC 1nF input filter, 2 discrete MLC 100nF power bypass caps.
3) A single X2Y 1nF input filter, a single X2Y 100nF power bypass cap.
X2Y configuration provided a nearly flat response above the ambient and up to
10 dB imrpoved rejection than the conventional MLCC configuration.
Amplifier Input Filter Example
In this example, a single Johanson X2Y
®
component was used to filter noise at the input of a DC
instrumentation amplifier. This reduced component count by 3-to-1 and costs by over 70% vs.
conventional filter components that included 1% film Y-capacitors.
Parameter
DC offset shift
Common mode rejection
X2Y
®
10nF
< 0.1 µV
91 dB
Discrete
10nF, 2 @ 220 pF
< 0.1 µV
92 dB
Comments
Referred to input
Source: Analog Devices, “A Designer’s Guide to Instrumentation Amplifiers (2nd Edition)” by Charles Kitchin and Lew Counts
12
www.johanson dielectrics.com
JOHANSON [ JOHANSON TECHNOLOGY INC. ]
