UM4701 Datasheet, PDF (5/11 Pages) Union Semiconductor, Inc. – Multi-line ESD/EMI Protection for Color LCD Interfaces

UM4701/4711/8701/8711
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 50 Ω system is shown in the figure below. It will be
analyzed in a 50Ω environment, so the source impedance and load impedance is 50 Ω. The
transfer functions then can be analyzed in terms of insertion loss (S21).
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 3.0 dB less than it is Pass Band
3.0 dB 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 UM4701/UM4711/UM8701/UM8711 is comprised of identical circuits consisting of a low
pass filter for EMI suppression and dual TVS diodes for ESD protection. The device is in an 8-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.
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http://www.union-ic.com Rev.01 Aug.2012
5/11