ADV7180 loses horizontal sync when tries to encode a picture with too bright light source

Hi, Dave,

DaveD wrote:

I asked about HS to rule out the ADV212-- since I've known it to have issues with some data patterns similar to what you are seeing.  I have not previously heard of this with the ADV7180 but your input circuit is not typical either.  Based on your other information, I doubt it has anything to do with that but I figured I would ask.  I meant that you were getting stable output-- it's just easier to see that with synchs than with time codes.

     I not use HSYNC/VSYNC in my debugging. But after your remark I think that known issue with HSYNC connected with my problem. There is another side of the problem. First version of my firmware used HDATA interface. When bad case happened EIRQFLG could not be settled to ‘1’. And when lamp went out, and ADC can normally capture the frame ADV212 set required EIRQFLG bit to ‘1’.

DaveD wrote:

Interesting that putting the divider circuit before the transformer would make the difference.  You can put your own clamp outside the circuit and then turn off the internal clamping with CCLEN (0x14 bit 4).  There isn't a way to adjust the clamp currents in the part though.

I placed my own clamp system instead of internal one. It was pullup 5 k resistor and pulldown 1 k resistor. The result became worse. Unfortunately, the design doesn’t let me to solder many times the seats near ADC. The current version of design (with divider before transformer) is more suitable for me.

Our company has another system for transmitting video base upon two-polar chip MAX7450 (nor MAX7451 nor MAX7452). It was placed between the cam and the input transformer. This system helps me to normalize video signal and get rid of blinking. May be this info helps somebody.

To make sure I give you main parameters of my transformer. Probably I helps to understand the reason:

Type – passive;

Input impedance – 75 Ohm;

Output impedance – 75 Ohm;

Frequency band – 0 – 7 MHz;

Input voltage    - 1,5 V;

Overshoot of frequency -2 dB;

A length of coaxial cable before the transformer  – approx. 2 m.

A length of microstrip path after transformer – 50 mm.

Thanks for your attention!

IgorS.

Hi, Dave,

DaveD wrote:

I asked about HS to rule out the ADV212-- since I've known it to have issues with some data patterns similar to what you are seeing.  I have not previously heard of this with the ADV7180 but your input circuit is not typical either.  Based on your other information, I doubt it has anything to do with that but I figured I would ask.  I meant that you were getting stable output-- it's just easier to see that with synchs than with time codes.

     I not use HSYNC/VSYNC in my debugging. But after your remark I think that known issue with HSYNC connected with my problem. There is another side of the problem. First version of my firmware used HDATA interface. When bad case happened EIRQFLG could not be settled to ‘1’. And when lamp went out, and ADC can normally capture the frame ADV212 set required EIRQFLG bit to ‘1’.

DaveD wrote:

Interesting that putting the divider circuit before the transformer would make the difference.  You can put your own clamp outside the circuit and then turn off the internal clamping with CCLEN (0x14 bit 4).  There isn't a way to adjust the clamp currents in the part though.

I placed my own clamp system instead of internal one. It was pullup 5 k resistor and pulldown 1 k resistor. The result became worse. Unfortunately, the design doesn’t let me to solder many times the seats near ADC. The current version of design (with divider before transformer) is more suitable for me.

Our company has another system for transmitting video base upon two-polar chip MAX7450 (nor MAX7451 nor MAX7452). It was placed between the cam and the input transformer. This system helps me to normalize video signal and get rid of blinking. May be this info helps somebody.

To make sure I give you main parameters of my transformer. Probably I helps to understand the reason:

Type – passive;

Input impedance – 75 Ohm;

Output impedance – 75 Ohm;

Frequency band – 0 – 7 MHz;

Input voltage    - 1,5 V;

Overshoot of frequency -2 dB;

A length of coaxial cable before the transformer  – approx. 2 m.

A length of microstrip path after transformer – 50 mm.

Thanks for your attention!

IgorS.