tda8757c NXP Semiconductors, tda8757c Datasheet - Page 12

• Manufacturer Part Number: tda8757c
• Description: Tda8757c Triple 8-bit Adc 205 Msps
• Manufacturer: NXP Semiconductors

Philips Semiconductors
8. Functional description
9397 750 10111
Preliminary data
8.1 Analog video inputs
8.2 Clamps
This triple high-speed 8-bit ADC is designed to convert RGB/YUV signals, coming
from an analog source, into digital data used by a LCD driver (pixel clock up to
205 MHz).
The RGB/YUV video inputs are externally AC-coupled and are internally
DC polarized.
The synchronization signals are also used by the device for the internal PLL and the
gain calibration.
If the green video signal has composite sync (sync on green) it is possible to extract
this composite sync by connecting the green signal to pin IN
the sync pulse amplitude is below 300 mV, the I
logic 1 (see
The composite sync is available at pin SOG
If this function is not used, pin IN
supply. In this event pin SOG
Three independent parallel clamping circuits are used to clamp the video input
signals on several black levels. The clamping levels may be set from
They are controlled by changing the values in three 9-bit registers: OFFSETR,
OFFSETG and OFFSETB (see
offset from 100 mV to 10 mV within 300 ns, and correct the total offset in 10 lines.
The clamping is done using the following principle: When a TTL positive going input
pulse is applied to pin CLP, three external capacitors are loaded independently by the
device in order to change the voltage level of each analog RGB input. The capacitors
are connected to pins CLP
63.5 to +64 LSBs (RGB) and from +120 to +136 LSBs in steps of
Fig 5. Sync level diagram.
Figure
300 mV
600 mV
150 mV
300 mV
to
to
Rev. 01 — 14 August 2002
5). The maximum amplitude for the sync pulse is 600 mV typical.
R
, CLP
O
is at LOW-level TTL.
Table
SOG
G
blank level
and CLP
blank level
should be connected to the analog power
150 mV comparison level
set by I
5). Each clamp must be able to correct an
80 mV comparison level
set by I
2
C-bus bit Slevel = 0
2
O
C-bus bit Slevel = 1
B
.
(TTL level compatible signal).
2
C-bus bit ‘Slevel’ has to be set to
005aaa009
© Koninklijke Philips Electronics N.V. 2002. All rights reserved.
Triple 8-bit ADC 205 Msps
SOG
TDA8757C
(AC-coupled). When
1
2
LSB (YUV).
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