TL1051 Datasheet, PDF (4/13 Pages) Texas Instruments – VIDEO PREPROCESSOR CIRCUIT

TL1051
VIDEO PREPROCESSOR CIRCUIT
SOCS032B – NOVEMBER 1991
detailed description
white-balance control
White balance in the monochrome mode can be adjusted with either terminal 2 (white-balance analog control)
or with terminals 3 and 4 (white-balance digital controls B and A, respectively). If analog control is selected,
terminals 3 and 4 should be left open and terminal 2 adjusted appropriately (see Figure 1 and Figure 2 for control
characteristics). The white balance is controlled per the following table:
CONTB
L
L
H
H
CONTA
L
H
L
H
VOLTAGE LEVEL ON WB
2.4 V
2.7 V
3V
3.5 V
RED
– 3 dB
– 1 dB
1 dB
3 dB
BLUE
– 4 dB
–1.5 dB
1.5 dB
4 dB
analog inputs RIN, GIN, BIN
The TI TL1593 sample-and-hold circuit is normally the source for these inputs. The source signals should be
ac coupled into the TL1051. Gain control should be used on at least two of the three channels in order to obtain
an optimum balance.
clamp level
Input terminals 9, 10, and 11 (CLPLVLB, CLPLVLG, and CLPLVLR, respectively) should initially be set at
approximately 2 V dc. The levels should then be balanced so that clock feedthrough on terminal 20 (YSW) is
minimized under dark conditions.
multiplexed switching
Input terminals 13, 14, and 15 (SWR, SWG, and SWB, respectively) are the TTL-level signals used to multiplex
the three channels.
clamping and process blanking
Input terminals 16, 17, and 18 (PCL1, PBL, and PCL2) are used for TTL clamp and blank signals. The dark
references are clamped by the PCL1 signal. Unwanted noise in the video signal is eliminated by the PBL signal.
The Y signal can then be reclamped with the PCL2 signal.
Depending on the application, gain and automatic gain control (AGC) may or may not be selected. The following
descriptions cover both selections.
YSW
YSW output (terminal 20): Fast sampling of the video input signals with the TTL multiplex signals generates this
high-bandwidth output without adjustable gain or AGC.
gain and AGC selected
YAGCIN input (terminal 21): If gain or AGC operation is selected, the YSW output (terminal 20) should be directly
connected to YAGCIN.
YAGC output (terminal 22): The multiplexed signal with controllable gain (controlled by the AGCCONT input)
is available at this terminal if terminals 20 (YSW) and 21 (YAGCIN) are connected. If further signal processing
is desired, this terminal should be ac coupled to terminal 23 (YCLAMP).
YCLAMP input (terminal 23): The Y signal from YAGC can be reclamped at this point by applying a wider clamp
pulse to terminal 18 (PCL2).
WCPCONT input (terminal 24): A dc voltage applied to this white clip control input causes the white clip function
to be performed on the Y signal. See Figure 4 for the clip control characteristics.
YALC output (terminal 25): If either AGC or automatic level control (ALC) is selected, the Y signal at this point
should be fed back to either the ALC or AGC block.
YOUT output (terminal 26): The white-clipped Y signal is available at this output.
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