Hello,

I have a question about resistor divider value of AIN pin of ADV7182 with differential CVBS.

Please see attached file "ADV7182_diff_CVBS_question".

Thank you.

Best regards.

Hello,

I have a question about resistor divider value of AIN pin of ADV7182 with differential CVBS.

Please see attached file "ADV7182_diff_CVBS_question".

Thank you.

Best regards.

You have to look at the whole path from the source to Ain1. The source will be 2x signal amplitude with a 75 Ohm series resistor. The sink should be 75 Ohm so you get 1/2 the source amplitude from the resistor divider network. Then Ain needs a lower amplitude where the 650 Ohm resistor divide comes in. Two 650 resistors in series parallel to the 75 Ohm resistor will effect the sink loading a bit. Draw up and look at all 4 resistors in the path to figure out what the values should be.

Remember the cable is a 75 Ohm cable so the source needs a 75 Ohms series resistor and the sink needs to be 75 Ohms equivalent.

What's important is what the pin voltages are. Normal pin single ended voltage will be 1.47Vpp * 51 / 75 = 1.0Vpp. In theory the connector voltage could be 100Vpp as long as you divide it down to the expected pin voltage of 1.0Vpp. If this voltage goes to low then you will not get peak colors and may start losing sync. If this voltage goes too high then you will start over driving the peaks.

The absolute peak analog input voltage is AVDD + 0.3V

Hello.

Thank you for your reply.

I can understand for case of single ended.

Please let me ask you a question about full differential input.About your following comment:

>For a full differential input the positive and negative input line would be 400mVppDoes the "400mVpp" mean minimum limit at the pin? or at the point before the divider network?

Thank you.

Best regards.

You have to look at the whole path from the source to Ain1. The source will be 2x signal amplitude with a 75 Ohm series resistor. The sink should be 75 Ohm so you get 1/2 the source amplitude from the resistor divider network. Then Ain needs a lower amplitude where the 650 Ohm resistor divide comes in. Two 650 resistors in series parallel to the 75 Ohm resistor will effect the sink loading a bit. Draw up and look at all 4 resistors in the path to figure out what the values should be.

Remember the cable is a 75 Ohm cable so the source needs a 75 Ohms series resistor and the sink needs to be 75 Ohms equivalent.