I'm using the AD8370 in a design. I'm using it as shown in figure 51 of the data sheet, DC coupled with +/- 2.5V supplies. I can't get an output from the VGA even though the power, serial control signals and input look good. The only thing I'm wondering about is the levels on the serial control signals. My control signals toggle between 0V and +2.5V. I'm wondering if they should toggle between -2.5V for a low and +2.5V for a high. Any ideas?