Datenblatt-Suchmaschine für elektronische Bauteile |
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GS1881-IDA Datenblatt(PDF) 8 Page - Gennum Corporation |
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GS1881-IDA Datenblatt(HTML) 8 Page - Gennum Corporation |
8 / 14 page 8 520 - 23 - 03 ODD/EVEN FIELD OUTPUT (pin 7 GS1881, GS4881) NTSC PAL and SECAM composite video standards are interlaced video schemes and therefore have odd and even fields. For odd fields the first broad vertical sync pulse is coincident with the start of horizontal, while for even fields the first broad vertical sync pulse starts in the middle of a horizontal line. Therefore by comparing the vertical sync with an internally generated horizontal sync the odd/even field information is determined. This output is clocked out by the falling edge of vertical sync. The odd/even output is low during even fields and high during odd fields. This method of detecting odd and even fields is very noise tolerant. Noise during the pre-equalizing pulses does not affect the output since the field decision is made at the beginning of the vertical interval. This noise immunity is displayed in Figure 15 in which an extra pre-equalizing pulse has been added to the video input with no negative effect on the odd/even field information. Video Input Odd/Even Output Even Odd HORIZONTAL OUTPUT (pin 7 GS4981) As mentioned above, the odd/even field output of the GS1881 and GS4881 is generated by comparing vertical sync with an internal horizontal sync signal. This horizontal sync signal is a true horizontal signal (i.e. maintained during the vertical interval) and is outputted on pin 7 for the GS4981. A delay of 190 ns from the video input and a width of 6.5 µs are typically characteristics for this signal. The windowing circuit which generates horizontal provides excellent impulse noise immunity as shown in Figure 16. This output buffer is an open collector stage with an internal 10 k Ω pull up resistor. Fig. 15 Odd/Even Output Impulse Noise Impulse Noise Video Input Horizontal Output Fig. 16 Horizontal Output |
Ähnliche Teilenummer - GS1881-IDA |
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Ähnliche Beschreibung - GS1881-IDA |
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