TC90A53N/F

2001-02-08 7/17

DESCRIPTION OF FUNCTIONS

(1) CLAMP (Input clamp)

Circuit used to Sync tip clamp composite signal.

Apply feedback clamp so that at Y / C separation, the minimum data value after A / D conversion is the

internally-fixed level.

(2) ADC (A / D converter)

High-speed series-parallel 8-bit A / D converter (Dynamic Range: 2.0V).

(3) 1 H memory

Line memory consisting of DRAM for 1 H delay. Two line memories configure a 3-line comb filter.

(4) VENH (Vertical enhancer circuit)

After coring (2LSB) the non-correlation component among the three lines of the luminance signal, this

block enhances the vertical outline. The enhance amount can be selected from three settings : large

The vertical enhance amount is added to the luminous signal obtained by subtracting the color signal

from the composite signal, then the luminous signal is output via the D / A converter. Note that if the

luminous signal is lower than the pedestal level (internally-fixed value), the vertical enhance amount is

not added to.

(5) BPF (Horizontal bandpass filter)

color signal.

The bandpass filter for outputting the color signal at a later stage can be switched on or off to select

output of a narrow- or wide-band color signal.

(6) DCF (Vertical dynamic comb filter)

Vertical bandpass filter which extracts the color signal by detecting vertical non-correlation. Using

Toshiba logic, determines the correlation among three lines. If no correlation, determines as the luminous

signal and suppresses output of the color signal.

(7) 1-line color dot interference reducer circuit

Improves color dot interference on a screen where only 1 line has color so that the C signal is processed as

the Y signal.

Extracts 1-line color dot component and the result is added to the output from the dynamic comb filter.

(8) RTIM (Clock / memory timing generator)

the timing signal necessary for memory.

(9) PLL (× 4 clock generator)

(10) DAC (D / A converter)

(11) Color killer circuit

When the input video signal is a monochrome image, this circuit enables effective use of the luminance

signal information regardless of whether there is a burst signal. It does this by preventing the chroma

signal output from the comb filter from being subtracted from the luminance signal.

While the VBI signal is active it is better not to use the comb function. Setting the KILLER pin to High

at this time enables the use of character multiplex and other signals from the Y output unchanged.

But since Vertical edge enhancement does not become OFF, be careful when using with Vertical edge

enhancement.