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.

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.