Vertical line in the camera system of OVM6946 is commonly happened in most of the product. We would like to share some experience in resolving this issue.

OVM6946 is a 1/18″ color CMOS analog 160 Kpixel (400 x 400 ) camera module with lens.

When a long extension cable is used, a vertical noise pattern is often found in the image, as shown in the below figure.

The OVM6946 has 4PINs connecting to the OV426 decoder chip, which are AVDD, AGND, XVCLK VOUT.

Clock input (4MHz)
Cable (50 Ohm impedance)
Vout signal (8MHz data rate) 

When the cable is too long, such as 1.5m~4m, or the cable quality is poor, the noise is easily introduced from the 4MHz input clock and coupled to the analog video (Vout), resulting in a vertical noise pattern.

Solutions

Cable characteristics is critical, need to follow the specification as below.

Relative signal wires should be shielded as per below diagram.

By strictly follow the above, our muC series camera with customized cable, the vertical stripes has been reduced dramatically. That is also the reason customer always like our image quality.