Category: Hardware
Product Number: AD9081
Hi,
We have the following observation in the AD9081-FMCA-EBZ Board. Kindly, help us resolve this query.
In AN-2065 document, it is mentioned that for DAC, the simulation results are optimal when the traces from the TCM1-83X+ Balun to the AD9081 IC pins is maintained for 50 ohms differential and
for ADC, when the traces are maintained for 100 ohms differential. We can find the same in the below images.
For DAC:-
For ADC:-
But in the given schematic from the ADI website, the Balun used is BALH-009SMG.
And the traces from the Balun to the AD9081 IC are routed for 50 ohm differential for both ADC and DAC. Is it because the simulation results for BALH yielded better performance for 50 ohm differential?
What bugs us is, both BALH-009SMG and TCM1-83X+ are 1:1 Baluns. So, shouldn't their performance be the same?
Also, In the simulation models that you have provided in the AN-2065 document, the termination resistors used for both ADC and DAC are given as 100 ohm. It can be seen below.
- If we are supposed to maintain 50 ohms for DAC, won't there be impedance mismatch if we give 100 ohm termination for DAC in the simulation model?
- And if we are maintaining the traces in the board-file as 50 ohms for ADC, it will again bring a mismatch if we give 100 ohm termination for ADC in the simulation model.
For DAC: For ADC:
Also, we have seen that in the AD9988_AD9986(which is similar to AD9081 apart from the difference in bandwidth and other specs) Board-files available in the website, we have seen that TCM1-83X+ Balun has been used and the ADC differential traces in that case have been maintained for 100 ohm differential and for DAC it is maintained for 50 ohm differential.
Edit Notes
The subject title has been changed[edited by: Utstech at 5:17 AM (GMT -5) on 7 Mar 2025]
