AnsweredAssumed Answered

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

Question asked by IgorS on Jan 19, 2011
Latest reply on Jan 26, 2011 by DaveD

Hello, Analog Devices,


My system has next structure:


CAM(SMX-F30BP) -> Galvanic Transformer 1 -> (ADV7180BCPZ) -> ADV212 -> MY DATA CHANNEL -> ADV212 -> ADV7391BCPZ -> Galvanic transformer 2 -> TV


When I direct my camera to bright light source (for examp, lamp), TV shows blinking picture (sometimes picture dissapears).

To catch this effect the camera shoud be directed to the upper left corner, or to the lower right ones. When I delete galvanic transformer 1 from the system, picture doesn't blinking.


Simple system CAM -> Galvanic Transformer -> TV works stable.


I think, that the problem in block connected with ADV7180. ADC cannot capture horisontal sync. Schematic you can see below:adv7180.jpg

The camera output video stream in PAL 720x576(50i) format. CVBS to Ain1.


I use following settings for the chip:


Register Name
Register number (in hex)
Register Value (in hex)
Input control0000
Video selection0180
Output control030C
Extended output control0424 (00100100)
Analog clamp control1412 (00010010)
Digital clamp control11560 (01100000)
Shapping filter control1741
Shapping filter control21893 (10010011)
Default Value Y0C52 (01010010)
Default Value C0DF8 (11111000)
Misc gain control2BA0
VS field control3102
AGC mode control2CAE (10101110)
Chroma gain control12DF4 (11110100)
Chroma gain control22E00
Luma gain control12FF2 (11110010)
Luma gain control23000
Drive strengthF400
IF comp controlF907 (00000111)
VS field pin control5801
Manual window control3DA2 (10100010)
BLM optimization3E6A
BGB optimization3FA0
CTI DNR control14DCF (11001111)
CTI DNR control24E0A
CTI DNR control4500A
Lock count51F6 (11110110)
PAL V beginE841
PAL V endE984
VBLANK control1EB6C (01011100)
VBLANK control2EC6C (01011100)
Peaking controlFBA0 (10000000)
Coring thresholdFC04 (00000100)
Register map hidden0E80
ADC configuration5581
Register map user0E00



I have made 2 situation (good case and bad case):


In good case picture from DAC was stable and we could measure normal clamp level from it (600 mV). (Fig. 28 from Datasheet). Photos are in attachement.

In bad case picture from DAC was blinking and we could see how clamp level have changed. ClampLevelDelta = 30-40 mV. Clamping system were inefficient.


May I change the power of current sources in ADV7180 clamp system? Will it help me solve this problem?

Thanks in advance.