UM4501 Datasheet, PDF (5/12 Pages) Union Semiconductor, Inc. – Multi-line ESD/EMI Protections for Signal Lines

UM4501/4511/6501/8501/8511
Applications Information
Insertion Loss
Insertion Loss (IL) is used to describe the transmission coefficient between two points in a circuit
often described in terms of dB. When examining S parameters, S21 is often described as insertion loss.
Insertion Loss and S21 will be used interchangeably from here on out. The insertion loss of a circuit
with VOUT and VIN would be expressed as
IL=S₂₁(dB)=20log(V_OUT/V_IN)
The setup for measuring insertion loss in a 50Ω system is shown in Figure 1. It will be analyzed in a
50Ω environment, so the source impedance and load impedance is 50Ω. The transfer functions then
can be analyzed in terms of insertion loss (S21).
TRACKING
GENERATOR
SPECTRUM
ANALYZER
50Ω
UNION EMI
FILTER
50Ω
vs
+
+
VIN
VOUT
-
-
Figure 1. Test Conditions: Source Impedance=50Ω
Load Impedance=50Ω
Input Power=0dBm
Cut Off Frequency
Cut off frequency is the frequency at which the signal strength is 3.0dB less than that of its Pass Band,
3.0dB of attenuation equates to half the original signal power. The Pass Band is the range of
frequencies that are allowed to “pass” through a filter with minimal attenuation. For our purposes it
starts from DC and ends at the cut off frequency.
Device Connection
The UM4501/UM4511/UM6501/UM8501/UM8511 is comprised of identical circuits each consisting
of a low pass filter for EMI suppression and dual TVS diodes for ESD protection. The device is in an
8-pin DFN, 12-pin DFN and 16-pin DFN package. Electrical connection is made to all the pins
located at the bottom of the device. A center tab serves as the ground connection. The device has a
flow through design for easy layout. All path lengths should be kept as short as possible to minimize
the effects of parasitic inductance in the board traces.
Ground Connection Recommendation
Parasitic inductance (L) present in the board layout will affect the filtering performance of the device.
As frequency (f) increases, the effect of the inductance becomes more dominant. This effect is given
by Equation 1.
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http://www.union-ic.com Rev.03 Apr.2016
5/12