Can apple tv output be forced to 720P?

I use an hdmi to vga converter to connect my apple tv 3 to my projector which only has an xga 1024 x 768 resolution, I used apple tv 2 before, it was alright, but with apple tv 3, I got d-sub out of range error and the projector cannot display.

I think the converter converts 1080p to a higher resolution, in order to keep using my projector, I have to change the apple tv output to the same as apple tv 2, which is 720p.