How to Generate a Tri-level signal. ..#3

seajayshore said:

Hey great thread. I'm just wondering how well your solution worked in the end? Did you manage to feel tri-level sync to the camera you were using OK?

I'm working on a very similar project where I'm trying to make a custom tri-level sync generator to feed a Blackmagic Micro Cinema Camera which accepts sync on a little expansion port.

For what it's worth I actually took apart a Blackmagic "mini converter sync generator" to see how it worked. It seems their approach is to use a component HD video encoder (specifically the ADV7393) to output a Y/Luma signal that contains the sync pulse already - presumably they just output a test-pattern as this chip is able to do that.

Copying this approach is more code than I hoped so I've been trying to find other solutions which is how i've stumbled on this thread.

Mod: link to old Thread.
https://forum.allaboutcircuits.com/threads/how-to-generate-a-tri-level-signal.163522

Click to expand...

Hello, I am implemented the circuit using a LTM2666 DAC to generate the high level and low level. I then used a LMH6738 triple output op amp. I tied the first op amp to the DAC high level output, tied the second op amp to the DAC low level output and the third opamp I tied to GND. I used a FPGA to control the three enables to each op ampl. I was able to generate the Vertical and Horizontal pules but my edges were more rounded that sharp.

Mod: Created new thread, link to old.
https://forum.allaboutcircuits.com/threads/how-to-generate-a-tri-level-signal-2.174282/post-1647294
Horizontal Pulse:


Here is the Vertical pulses:


I am testing the circuit with a camera now to see if the camera will lock to this signal. I have my doubts.
Thank you for mentioning the ADV7393 device. I see on page 80 of the datasheet they show Tri-level synch generation. I also see there is a Eval kit, "EVAL-ADV739X Evaluation Platform " which may be a good idea to purchase. However, the ADV7393 does not support 1080p only 1080i. I will need to find one that support 1080p at 60Hz.

Thank you very much,
Joe