ch7019 Chrontel, ch7019 Datasheet - Page 17

• Manufacturer Part Number: ch7019
• Description: Ch7019 Tv Encoder / Lvds Transmitter
• Manufacturer: Chrontel

CHRONTEL
2.3.3
The CH7019 allows the subcarrier frequency to be accurately generated from a 14.31818 MHz crystal oscillator, leaving
the subcarrier frequency independent of the graphics pixel clock frequency. As a result, the CH7019 may be used with
most VGA chips (with an appropriate digital interface) since the CH7019 subcarrier frequency can be generated without
being dependent on the precise pixel rates of VGA controllers. This feature is important since even a ±0.01% subcarrier
frequency variation is enough to cause some televisions to lose color lock.
In addition, the CH7019 has the capability to genlock the color burst signal to the VGA horizontal sync frequency, which
enables a fully synchronous system between the graphics controller and the television. When genlocked, the CH7019 can
stop “dot crawl” motion (for composite NTSC modes), thus eliminating the annoyance of moving borders. Both of these
features are under programmable control through the register set.
2.3.4
Composite and S-Video outputs are supported in either NTSC or PAL format. The general parameters used to
characterize these outputs are listed in Table 11 and shown in Figure 9. (See Figure 12 through Figure 17 for illustrations
of composite and S-Video output waveforms).
ITU-R BT.470 Compliance
The CH7019 is predominantly compliant with the recommendations called out in ITU-R BT.470. The following are the
only exceptions to this compliance:
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201-0000-048
The frequencies of Fsc, Fh, and Fv can only be guaranteed in clock/sync master mode, not in clock/sync slave mode
when the graphics device generates these frequencies.
It is assumed that gamma correction, if required, is performed in the graphics device which establishes the color
reference signals.
All modes provide the exact number of lines called out for NTSC and PAL modes respectively, except mode 21,
which outputs 800x600 resolution, scaled by 3:4, to PAL format with a total of 627 lines (vs. 625).
Chroma signal frequency response will fall within 10% of the exact recommended value.
Pulse widths and rise/fall times for sync pulses, front/back porches, and equalizing pulses are designed to
approximate ITU-R BT.470 requirements, but will fall into a range of values due to the variety of clock frequencies
used to support multiple operating modes.
Color Burst Generation
NTSC and PAL Operation
Rev. 2.4,
12/18/2006
CH7019B
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