Questions about dc-coupled application of AD9208

Hello,

My customer is using AD9208 and they are considering to change ac-coupled method  to dc-coupled method for improving SNR/SFDR.

And as Figure 50 & Figure 56 in your datasheet , they know that dc-coupled configuration can be accomplished by External VCM  and AMP configuration with some register settings 

About these above comments, they have some questions.

(dc-coupled configuration using External VCM  and AMP configuration)

1.  Could they control the value  of External VCM (Common Mode Voltage) the same as the full range of Common mode voltage (Vcm : 1.32V to 1.52V) in table 1?

2. If they can do above thing, how do they control these values (from 1.32V to 1.52V)?

3. If they can't do this, would you share limitation of controllable value of External VCM?

4. If you have any reference schematic with External VCM  and AMP configuration, please share your reference schematic to them.

   Or please share your recommended part and circuit for this configuration.

5. For above things (Improving SNR and SFDR using dc-coupled), if you have any opinions, please advise them

Regards,

Se-woong

Parents
  • +1
    •  Analog Employees 
    on Mar 17, 2021 10:51 AM

    1. the input common mode (at VINA+/- or VINB+/-) voltage will change based on the buffer current setting. It can change from a typical of 1.32V to around 1.52V. If using the export VCM feature, please follow the instructions as described in the datasheet. The output voltage should match what is at the input pins. 

    2. Read the datasheet

    3. no limitation 

    4. ADL5569

    5. follow datasheet guidelines for the amplifier and adc

    please provide more details about the application. 

Reply
  • +1
    •  Analog Employees 
    on Mar 17, 2021 10:51 AM

    1. the input common mode (at VINA+/- or VINB+/-) voltage will change based on the buffer current setting. It can change from a typical of 1.32V to around 1.52V. If using the export VCM feature, please follow the instructions as described in the datasheet. The output voltage should match what is at the input pins. 

    2. Read the datasheet

    3. no limitation 

    4. ADL5569

    5. follow datasheet guidelines for the amplifier and adc

    please provide more details about the application. 

Children
No Data