el1882c Intersil Corporation, el1882c Datasheet - Page 10

• Manufacturer Part Number: el1882c
• Description: Sync Separator W/50% Slice, Agc
• Manufacturer: Intersil Corporation

default delay time, approximately 60µs after the last falling
edge of the vertical equalizing phase for R
Odd/Even
Because a typical television picture is composed of two
interlaced fields, there is an odd field that includes all the
odd lines, and an even field that consists of the even lines.
This odd/even field information is decoded by the EL1882C
during the end of picture information and the beginning of
vertical information. The odd/even circuit includes a T-flip-
flop that is reset during full horizontal lines, but not during
half lines or vertical equalization pulses. The T-flip-flop is
clocked during each falling edge of these half hperiod
pulses. Even fields will toggle until a low state is clocked to
the odd/even pin 7 at the beginning of vertical sync, and odd
fields will cause a high state to be clocked to the odd/even
pin at the start of the next vertical sync pulse. Odd/even can
be ignored if using non-interlaced video, as there is no
change in timing from one field to the next.
R
An external R
ground, produces a reference current that is used internally
as the timing reference for vertical sync width, vertical sync
SET
SET
resistor, connected from R
10
SET
SET
= 681k:.
pin 6 to
EL1882C
FIGURE 5.
default delay, burst gate delay and burst width. Decreasing
the value of R
turn decreases reference times and pulse widths. A higher
frequency video input necessitates a lower R
Chroma Filter
When the EL1882 is used in composite color systems, a
chroma filter is required at the video input. This is so
because the color burst signal extends to the 50% point of
the sync pulse (-20 IRE). Since the EL1882 slices at the
50% level, a chroma filter is required to attenuate the color
burst signal to a point above the 50% level. Without this filter
false sync triggering may occur during color burst. An
example chroma filter is shown in Figure 5. It can be
implemented very simply and inexpensively with a series
resistor of 620: and a parallel capacitor of 500pF, which
gives a single pole roll-off frequency of about 500kHz. This
sufficiently attenuates the 3.58MHz (NTSC) or 4.43MHz
(PAL) color burst signal, yet passes the approximately
15kHz sync signals without appreciable attenuation. A
chroma filter will increase the propagation delay from
composite sync to outputs.
SET
increases the reference current, which in
SET
value.