Video Inputs Electrical Specifications

The VIDEO connector has 4 identical Video Inputs. Each port has two pins named VID_INxx and VRN_INxx respectively, where xx is a number ranging from 1 to 4. The "hot conductor" of the transmission line transporting the video signal xx has to be connected to the VID_INxx pin, while the "cold conductor" of the transmission line has to be connected to the corresponding VRN_INxx pin. If the transmission line is a coaxial line, the "hot conductor" is the inner conductor, and the "cold conductor" is the outer conductor.

A switchable 75Ω termination resistor is inserted directly across VID_INxx and VRN_INxx. The termination resistor can be disconnected by a DIP switch.

The factory settings of the termination resistor DIP switch are ON.

The video signal flows through a common-mode choke which attenuates any common-mode noise present on the video signal. The VRN_INxx pin is connected to the analog GND through one winding of the common-mode choke. The VID_INxx pin is connected to the second winding.

The filtered video signal (slightly attenuated by the 1kΩ/10kΩ resistor network) is AC-coupled to a video input of the video decoder. The 1 kΩ resistor protects the video decoder input against excessive currents in case of abnormal signal levels applied on the Video inputs.

The filtered video signal is also AC-coupled to an input of the video multiplexer circuit.

U4H264PCI104VideoInputCircuit

Video Input circuit

Video inputs - DC characteristics

Parameter

Min

Typ.

Max

Units

Input voltage range - Absolute max rating

-0.55

 

+2.2

V

Input impedance - Terminator OFF

 

11

 

Input impedance - Terminator ON

 

75

 

Ω

For a correct operation of the video decoder, the video signal must satisfy all following electrical requirements.

Video signal electrical requirements

Parameter

Min

Typ.

Max

Units

Overall peak-to-peak amplitude

0.5

1.0

1.5

V

Sync amplitude

150

300

400

mV

Rise/Fall time of sync edges

50

 

300

ns

Lower video signal amplitudes are not recommended.

The signal attenuation induced by the 1kΩ/10kΩ resistor network circuit is compensated by the front-end amplifier in the input stage of the video decoder.