EL4583
Pin Descriptions
PIN
NUMBER
1
2
PIN NAME
PIN FUNCTION
Filter Cut-Off A resistor R
F
connected between this input and ground determines the input filter characteristic. Increasing R
F
increases the filter 3.58MHz color burst attenuation. See the typical performance characteristics.
Set Detect
Level
A resistor R
LV
connected between pin 2 and ground determines the value of the minimum signal which triggers the
loss of signal output on pin 10. The relationship is V
P
MIN = 0.75RLV/R
SET
, where V
P
MIN is the minimum detected
sync pulse amplitude applied to pin 4. See the typical performance characteristics.
3
4
Composite This output replicates all the sync inputs on the input video.
Sync Output
Filter Input
The filter is a 3 pole active filter with a gain of 2, designed to produce a constant phase delay of nominally 260ns with
signal amplitude. Resistor RF on pin 1 controls the filter cut-off. An internal clamp sets the minimum voltage on pin
4 at 1.55V when the input becomes low impedance. Above the clamp voltage, an input current of 1µA charges the
input coupling capacitor. With loss of signal, the current source switches to a value of 10µA, for faster signal recovery.
5
Vertical Sync The vertical sync output is synchronous with the first serration pulse rising edge in the vertical interval of the input
Output
signal and ends on the trailing edge of the first equalizing Output pulse after the vertical interval. It will therefore be
slightly more than 3H lines wide.
Digital
Ground
This is the ground return for digital buffer outputs.
6
7
8
9
10
Filter Output Output of the active 3 pole filter which has its input on pin 4. It is recommended to ac couple the output to pin 8.
Video Input
This input can be directly driven by the signal if it is desired to bypass the filter, for example, in the case of strong
clean signals. This input is 6dB less sensitive than the filter input.
Level Output This pin provides an analog voltage which is nominally equal to twice the sync pulse amplitude of the video input
signal applied to pin 4. It therefore provides an indication of signal strength.
No Signal
Detect
Output
This is a digital output which goes high when either a) loss of input signal or b) the input signal level falls below a
predetermined amplitude as set by R
LV
on pin 2. There will be several horizontal lines delay before the output is
initiated.
11
Burst/Back The start of back porch output is triggered on the trailing edge of normal H sync, and on the rising edge of serration
Porch Output pulses in the vertical interval. The pulse is timed out internally to produce a one-shot output. The pulse width is a
function of R
SET
. This output can be used for d.c. restore functions where the back porch level is a known reference.
R
SET
The current through the resistor R
SET
determines the timing of the functions within the I.C. These functions include
the sampling of the sync pulse 50% point, back porch output and the 2H eliminator. For faster scan rates, the resistor
needs to be reduced inversely. For NTSC 15.7kHz scan rate R
SET
is 681k 1%. R
SET
must be a 1% resistor.
Odd-even output is low for even field and high for odd field. The operation of this circuit has been improved for
rejecting spurious noise pulses such as those present in VCR signals.
The internal circuits are designed to have a high immunity to supply variations, although as with most I.C.s a 0.1µF
decoupling capacitor is advisable.
12
13
14
15
Odd/Even
Output
V
DD
5V
Horizontal
This output produces only true H pulses of nominal width 5µs. The leading edge is triggered from the leading edge
Sync Output of the input H sync, with the same prop. delay as the composite sync. The half line pulses present in the input signal
during vertical blanking are eliminated with an internal 2H eliminator circuit.
Analog
Ground
This is the ground return for the signal paths in the chips, R
SET
, R
F
and R
LV
.
16
3
FN7173.3
November 12, 2010
INTERSIL [ INTERSIL CORPORATION ]
