THS7375IPWR datasheet(18/36 Pages) TI

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TYPICAL CONFIGURATION AND VIDEO

75 W

Y'/G'Out

CVBS/Sync

CVBS

+3.3V

DaVinci

DAC/Encoder

SDTV

CVBS

S-Video

Y'P' P'

R'G'B'

Y'/G'

P’ /B'

P’ /R'

CH1OUT

CH2OUT

CH3OUT

CH4OUT

S+

BYPASS

CH1IN

CH2IN

CH3IN

CH4IN

GND

DISABLE

THS7375

ToGPIOController

orGND

75 W

P' /B'Out

75 W

P' /R'Out

75 W

330 F

+3Vto+5V

THS7375

SBOS449 – SEPTEMBER 2008......................................................................................................................................................................................... www.ti.com

This rationale is also used for the chroma (C') term.

TERMINOLOGY

Chroma is derived from the nonlinear R'G'B' terms

and thus it is also nonlinear. Chominance (C) is

A typical application circuit that uses the THS7375 as

derived from linear RGB, giving the difference

a video buffer is shown in Figure 46. It shows a DAC

between chroma (C') and chrominance (C). The color

encoder

driving

the

input

channels

the

difference signals (P'B/P'R/U'/V') are also referenced

THS7375. One channel is a composite video (CVBS)

this

way

denote

the

nonlinear

(gamma

channel of a standard definition (SD) video system.

corrected) signals.

The other channels are the component video Y'P'BP'R

(sometimes labeled Y'U'V' or incorrectly labeled

R'G'B' (commonly mislabeled RGB) is also called

Y'C'BC'R) signals of a 480i or 576i system. These

G'B'R' (again commonly mislabeled as GBR) in

channels could easily be the S-Video Y'/C' channels

professional video systems. The SMPTE component

or the R'G'B' channels of a SCART system.

standard stipulates that the luma information is

placed on the first channel, the blue color difference

Note that the Y' term is used for the luma channels

is placed on the second channel, and the red color

throughout this document rather than the more

difference signal is placed on the third channel. This

common luminance (Y) term. The reason for this

configuration

consistent

with

the

Y'P'BP'R

usage is to account for the definition of luminance as

nomenclature. Because the luma channel (Y') carries

stipulated

the

International

Commission

the sync information and the green channel (G') also

Illumination (CIE). Video departs from true luminance

carries the sync information, it makes logical sense

because a nonlinear term, gamma, is added to the

that G' be placed first in the system. Furthermore,

true RGB signals to form R'G'B' signals. These R'G'B'

because the blue color difference channel (P'B) is

signals are then used to mathematically create luma

next and the red color difference channel (P'R) is last,

(Y'). Thus, luminance (Y) is not maintained, providing

then it also makes logical sense to place the B' signal

a difference in terminology.

on the second channel and the R' signal on the third

channel respectfully. Thus, hardware compatibility is

better achieved when using G'B'R' rather than R'G'B'.

Note that for many G'B'R' systems, sync is embedded

on all three channels, but this configuration may not

always be the case in all systems.

Figure 46. Typical SDTV CVBS/Y'P'BP'R Inputs from DC-Coupled Encoder/DAC

with AC-Coupled Line Driving

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