THS7374 Datasheet, PDF (27/37 Pages) Texas Instruments – 4-Channel SDTV Video Amplifier with 6th-Order Filters and 6-dB Gain

THS7374
www.ti.com....................................................................................................................................................................................................... SLOS590 – JULY 2008
EVALUATION MODULE
To evaluate the THS7374, an evaluation module
(EVM) is available. The EVM allows for testing the
THS7374 in many different cnfiguration. 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 single supply from 2.85 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 about 1.4 V for proper operation. Failure to be
within this range will saturate and/or clip the output
signal. If the input range is beyond this, or if the
signal voltage is unknown, or coming from a current
sink DAC, then ac input configuration is desired. This
is easily accomplished with the EVM by simply
replacing Z1, Z2, Z3, and Z4 0-Ω resistors with
0.1-µF capacitors.
For ac-coupled input and sync-tip clamp (STC)
functionality commonly used for CVBS, s-video Y',
component Y' signals, and R'G'B' signals with
embedded sync, then 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, and non-sync embedded
R'G'B' signals, then a pull-up resistor should be
added to the signal on the EVM. This is easily done
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
embeed 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 C17—with 0-Ω resistors works well. Removing
the 470-µF capacitors is optional, but removing them
from the EVM will eliminate a few picofarads of stray
capacitance on each signal path which may be
desirable.
The THS7374 incorporates an easy method to
configure the bypass mode and the disable mode.
The use of JP1 controls the disable feature while JP4
controls the bypass feature. While there is a space on
the EVM for JP2 and JP3, these are not utilized for
the THS7374. Connection of JP1 to GND applies 0 V
to the disable pin and the THS7374 operates
normally. Moving JP1 to +V_S causes the THS7374 to
be in disable mode. Connection of JP4 to GND
places the THS7374 in filter mode while moving JP4
to +V_S places the THS7374 in bypass mode.
Figure 43 shows the THS7374EVM schematic.
Figure 44 and Figure 45 illustrate the two layers of
the EVM PCB, incorporating standard high-speed
layout practices. Table 2 lists the bill of materials as
supplied from Texas Instruments.
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): THS7374
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