THS7320 Datasheet, PDF (21/35 Pages) Texas Instruments – 3-Channel ED Filter Video Amplifier with 4-V/V Gain

THS7320
www.ti.com
SBOS565B – JULY 2011 – REVISED SEPTEMBER 2012
VIDEO INPUT OVERVOLTAGE PROTECTION
The THS7320 is built using a very high-speed, complementary, bipolar CMOS process. The internal junction
breakdown voltages are relatively low for these very small geometry devices. These breakdowns are reflected in
the Absolute Maximum Ratings table. All input and output device pins are protected with internal electrostatic
discharge (ESD) protection diodes to the power supplies, as shown in Figure 55.
These diodes provide moderate protection to input overdrive voltages above and below the supplies as well. The
protection diodes can typically support 30 mA of continuous current when overdriven.
+V_S
External
Input/Output
Pin
Internal
Circuitry
Figure 55. Internal ESD Protection For Video Section
TYPICAL VIDEO CONFIGURATION AND VIDEO TERMINOLOGY
A typical application circuit using the THS7320 as a video buffer is shown in Figure 56. It shows a DAC or
encoder dc-coupled to the input channels of the THS7320 and the output of the THS7320 dc-coupled to the
video line. These signals can be NTSC, PAL, or SECAM signals including composite video baseband signal
(CVBS), S-Video Y'C', component Y'P'_BP'_R video, broadcast G'B'R' video, or computer R'G'B' video signals.
Channel 1
Channel 2
Channel 3
x2
R
x2
R
x2
R
Level
Shift
Level
Shift
Level
Shift
3 Pole
20 MHz
LPF
3 Pole
20 MHz
LPF
3 Pole
20 MHz
LPF
6 dB
6 dB
6 dB
75 W ^{Out 1}
75 W ^{Out 2}
75 W ^{Out 3}
75 W
75 W
75 W
+2.6 V to +5 V Enable
Figure 56. Typical THS7320 Video Section with DC-Coupled Encoder/DAC and DC-Coupled Line Driving
Note that the Y’ term is used for the luma channels throughout this document rather than the more common
luminance (Y) term. This usage accounts for the definition of luminance as stipulated by the International
Commission on Illumination (CIE). Video departs from true luminance because a nonlinear term, gamma, is
added to the true RGB signals to form R’G’B’ signals. These R’G’B’ signals are then used to mathematically
create luma (Y’). Thus, luminance (Y) is not maintained, providing a difference in terminology.
This rationale is also used for the chroma (C’) term. Chroma is derived from the nonlinear R’G’B’ terms and,
thus, it is nonlinear. Chrominance (C) is derived from linear RGB, giving the difference between chroma (C’) and
chrominance (C). The color difference signals (P’_B/P’_R/U’/V’) are also referenced in this manner to denote the
nonlinear (gamma corrected) signals.
Copyright © 2011–2012, Texas Instruments Incorporated
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