Datasheet

75 W
Y'Out
CVBSOut
CVBS
R
Y'/G'
R
P’ /B'
B
R
P’ /R'
R
R
1
2
3
4
5
6
7
14
13
12
11
10
9
8
CVBSOUT
HD CH1OUT
HD CH2OUT
HDCH3OUT
V
S+
HDBYPASS
NC
CVBSIN
HDCH1IN
HDCH2IN
HDCH3IN
GND
DISABLE
NC
THS7373
ToGPIOController
orGND
75 W
75 W
P' Out
B
75 W
75 W
P' Out
R
75 W
75 W
75 W
+3Vto+5V
SOC /DAC/Encoder
THS7373
www.ti.com SBOS506A –DECEMBER 2009–REVISED AUGUST 2012
TYPICAL CONFIGURATION AND VIDEO Note that the Y’ term is used for the luma channels
TERMINOLOGY throughout this document rather than the more
common luminance (Y) term. This usage accounts for
A typical application circuit using the THS7373 as a
the definition of luminance as stipulated by the
video buffer is shown in Figure 98. It shows a DAC or
International Commission on Illumination (CIE). Video
encoder driving the input channels of the THS7373.
departs from true luminance because a nonlinear
One channel is a CVBS connection using the
term, gamma, is added to the true RGB signals to
standard definition (CVBS) video filters. This signal
form R’G’B’ signals. These R’G’B’ signals are then
can be an NTSC, PAL, or SECAM video signal. The
used to mathematically create luma (Y’). Thus,
other three channels are the component video
luminance (Y) is not maintained, providing a
Y’/P’
B
/P’
R
(sometimes labeled Y’U’V’ or incorrectly
difference in terminology.
labeled Y’/C’
B
/C’
R
) video signals. These signals are
typically 720p, 1080i, or up to 1080p30 signals. If the This rationale is also used for the chroma (C’) term.
video DAC samples at greater than 74.25 MHz, then Chroma is derived from the nonlinear R’G’B’ terms
480i/576i or 480p/576p signals are also supported and, thus, it is nonlinear. Chominance (C) is derived
while effectively minimizing DAC images. Because from linear RGB, giving the difference between
the HD filters can be bypassed, other formats such as chroma (C’) and chrominance (C). The color
1080p60 (also known as Full-HD or True-HD) or difference signals (P’
B
/P’
R
/U’/V’) are also referenced
computer R'G'B' resolutions up to QXGA can also be in this manner to denote the nonlinear (gamma
supported with the THS7373. corrected) signals.
Figure 98. Typical Four-Channel System Inputs from DC-Coupled Encoder/DAC
with DC-Coupled Line Driving
Copyright © 2009–2012, Texas Instruments Incorporated 31