ADA4420-6

Hi,

My name is Mike McGonegal; I'm the ADI applications engineer supporting the ADA4420-6 video filter.

The video bandwidth of the ADA4420-6 HD channels is about 26 MHz, which is sufficient for 1080i (1920 x 1080 @ 30 Hz) or 720p (1280 x 720 @ 60 Hz) HDTV.  Both of these use a sampling rate of 74.25 MHz. For your application (SXGA 1280 x 1024 @ 60 Hz), the video DAC sampling rate would be around 108 MHz for 1x oversampling, and the required video bandwidth would be about 44 MHz.

For this reason, I would not recommend the ADA4420-6 for this application. I'd suggest maybe a triple video op-amp such as the ADA4862-3 with passive (or a combination of active and passive) reconstruction filters. If the sampling rate is 108 MHz (1x), you'll need anywhere from a 4th to 6th order filter, depending on how much attenuation is required at the sampling frequency.  With 2x oversampling, you could probably get away with a 2nd or 3rd order filter.  A second order filter could be implemented actively using a Sallen-Key configuration for the op-amps.  Additional passive filtering could be used at the output to achieve the required attenuation.

If you have any additional questions about ADI video filters or amplifiers, please let me know.