3

FN7173.3

November 12, 2010

Pin Descriptions

PIN

NUMBER

PIN NAME

PIN FUNCTION

1

increases the filter 3.58MHz color burst attenuation. See the typical performance characteristics.

2

Set Detect

Level

sync pulse amplitude applied to pin 4. See the typical performance characteristics.

3

Composite

Sync Output

This output replicates all the sync inputs on the input video.

4

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

Output

The vertical sync output is synchronous with the first serration pulse rising edge in the vertical interval of the input

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.

6Digital

Ground

This is the ground return for digital buffer outputs.

7

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.

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.

9

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.

10

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

initiated.

11

Burst/Back

Porch Output

The start of back porch output is triggered on the trailing edge of normal H sync, and on the rising edge of serration

pulses in the vertical interval. The pulse is timed out internally to produce a one-shot output. The pulse width is a

12

the sampling of the sync pulse 50% point, back porch output and the 2H eliminator. For faster scan rates, the resistor

13

Odd/Even

Output

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.

14

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.

15

Horizontal

Sync Output

This output produces only true H pulses of nominal width 5µs. The leading edge is triggered from the leading edge

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.

16

Analog

Ground

EL4583