Under what circumstances can the resistor divider network at the input to the ADV7180 (see attached figure) be omitted?
The purpose of the resistor divider is to approximately half the inputted video signal voltage to the ADV7180. This prevents clipping and makes the ADV7180 robust to variations in input voltages. The gain blocks within the ADV7180 compensates for the halving of the input voltage.
Note that resistor divider also supplies the 75 Ohm end termination that is needed for some applications.
However the resistor divider network can be omitted if the input video voltage is:
Note that the 100nF AC coupling capacitor is vital to the correct operation of the ADV7180 and cannot be omitted. The purpose of this capacitor is to remove the DC bias of the inputted video signal. The internal clamping circuitry of the ADV7180 restores this DC value.
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