AD9176 Pin J6 separate power

Hi,

Is there any special reason for separating AD9176 Pin J6 power supply (AVDD1V0_J6) from the rest of the AVDD1V0 power on AD9172-FMC-EBZ RevC Schematic?

Can these supplies be joined together?

Same question about AD9176 Pin K7 (AVDD1V8_K7) and AVDD1V8.

Thanks a lot and Best Regards,

rise.



Found another strange connection - Pin K7
[edited by: rise at 10:36 PM (GMT -5) on 30 Nov 2018]

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  • +1
    •  Analog Employees 
    on Oct 14, 2019 6:30 PM

    Assumed answered offline.  Let us know if there are further questions.

  • Hi, I'm also interested in this issue. Is there somewhere information on why those two pins are separated from the rest in AD9172-FMC-EBZ? There is no indication in the AD9172 datasheet that it would be necessary.

  • 0
    •  Analog Employees 
    on Feb 8, 2021 11:08 PM in reply to Teemu

    Hi Teemu,

    J6 is related to the on-chip DAC clock PLL, so it was suggested that it is safer to isolate it from the analog output supply (AVDD1.0). It may help reduce spurious in some cases. 

    The same idea applies to K7. 

    It is better to keep the supplies isolated. But the FB could be replaced with a 0ohm res, if this has no impact in particular applications. 

    In hindsight, it may have been better to show these pins in the datasheet as separate power domains. 

    Not questioned here, but there is another similar domain, labeled DVDD_F4_F9. Not having this domain isolated from DVDD may result in low spurs, whose location in frequency would depend on the interpolation rate (coupling from DVDD into DVDD_F4_F9). The spurs are too low and are out of band for most applications.  

    Landsman  

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  • 0
    •  Analog Employees 
    on Feb 8, 2021 11:08 PM in reply to Teemu

    Hi Teemu,

    J6 is related to the on-chip DAC clock PLL, so it was suggested that it is safer to isolate it from the analog output supply (AVDD1.0). It may help reduce spurious in some cases. 

    The same idea applies to K7. 

    It is better to keep the supplies isolated. But the FB could be replaced with a 0ohm res, if this has no impact in particular applications. 

    In hindsight, it may have been better to show these pins in the datasheet as separate power domains. 

    Not questioned here, but there is another similar domain, labeled DVDD_F4_F9. Not having this domain isolated from DVDD may result in low spurs, whose location in frequency would depend on the interpolation rate (coupling from DVDD into DVDD_F4_F9). The spurs are too low and are out of band for most applications.  

    Landsman  

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