THS7373_10 Datasheet, PDF (41/50 Pages) Texas Instruments – 4-Channel Video Amplifier with 1-SD and 3-HD Sixth-Order Filters and 6-dB Gain

THS7373
www.ti.com
EVALUATION MODULE
SBOS506 – DECEMBER 2009
To evaluate the THS7373, an evaluation module
(EVM) is available. The THS7373EVM allows for
testing the THS7373 in many different configurations.
Inputs and outputs include BNC connectors
commonly found in video systems, along with 75-Ω
input termination resistors, 75-Ω series source
termination resistors, and 75-Ω characteristic
impedance traces. Several unpopulated component
pads are found on the EVM to allow for different input
and output configurations as dictated by the user.
This EVM is designed to be used with a single supply
from 2.6 V up to 5 V.
The EVM default input configuration sets all channels
for dc input coupling. The input signal must be within
0 V to approximately 1.4 V for proper operation.
Failure to be within this range saturates and/or clips
the output signal. If the input range is beyond this, if
the signal voltage is unknown, or if coming from a
current sink DAC, then ac input configuration is
desired. This option is easily accomplished with the
EVM by simply replacing the Z₁ through Z₄ 0-Ω
resistors with 0.1-μF capacitors.
For an ac-coupled input and sync-tip clamp (STC)
functionality commonly used for CVBS, s-video Y',
component Y' signals, and R'G'B' signals, no other
changes are needed. However, if a bias voltage is
needed after the input capacitor which is commonly
needed for s-video C', component P'_B and P'_R
signals, then a pull-up resistor should be added to the
signal on the EVM. This configuration is easily
achieved by simply adding a resistor to any of the
following resistor pads: RX1, RX3, RX5, or RX7. A
common value to use is 3.3 MΩ. Note that even
signals with embedded sync can also use bias mode
if desired.
The EVM default output configuration sets all
channels for ac output coupling. The 470-μF and
0.1-μF capacitors work well for most ac-coupled
systems. However, if dc-coupled output is desired,
then replacing the 0.1-μF capacitors (C12, C14, C16,
and/or C17) with 0-Ω resistors works well. Removing
the 470-μF capacitors is optional, but removing them
from the EVM eliminates a few picofarads of stray
capacitance on each signal path which may be
desirable.
The THS7373 incorporates an easy method to
configure the bypass mode and the disable mode.
The use of JP1 controls the disable feature and JP4
controls the HD channels filter/bypass mode. While
there is a space on the EVM for JP2 and JP3, these
are not used for the THS7373.
Connection of JP1 to GND applies 0 V to the disable
pin and the THS7373 operates normally. Moving JP1
to +V_S causes all channels of the THS7373 to be in
disable mode.
Connection of JP4 to GND places the THS7373 HD
channels in filter mode while moving JP4 to +V_S
places the THS7373 HD channels in bypass mode.
The THS7373EVM also includes a method to improve
the ESD performance of all the analog inputs and
outputs beyond the ratings shown in the Absolute
Maximum Ratings table. By using very low cost
BAV99 diodes, the EVM has the ability to pass IEC
±8kV surge testing. Another common protection diode
commonly utilized is the BAT54S which also achieves
the same surge suppression performance as the
BAV99 diodes.
Figure 104 shows the THS7373EVM schematic.
Figure 105 and Figure 106 illustrate the two layers of
the EVM PCB, incorporating standard high-speed
layout practices. Table 6 lists the bill of materials as
the board comes supplied from Texas Instruments.
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): THS7373
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