Hi all,

I checked the datasheet @ AD9684-500 & AD9680-500 about the each differential input configurations.

Using same transformer 50ohm balun, but different termination resister R2, 25ohm or 50ohm.

The available span is same 2.06 V p-p differential to each ADC.

Why not, R2 difference?

Best Regards,

sss

Hi,

The front end networks were optimized primarily for ADC performance in SNR/SFDR specs. when using the ETC1-1-13, a 10/50ohm split gave good performance for the AD9680 whereas the 10/25ohm split gave good performance for the AD9684. the 10/25ohm split will work for the AD9680 and provide same performance, but it has higher insertion loss. so we decided to stick with the 10/50ohm split since the performance wasnt degraded.

The ETC1-1-13 is a 1:1 impedance ratio transformer. so for a good match, the differential impedance on the output should be ~50ohms, hence the 2x 10ohms with 2x 25ohms.

Thanks

Umesh