The AGND and DGND Issue inAD9954

Hi, I read the datasheet of AD9954 and have such questions below,

1、I have found that in the schematic of AD9954 eval board, AGND and DGND share the same ground plane (GND) as figure 1 shown. So

But the layout consideration in the datasheet recommends the AGND and DGND shoule be kept seperate on the localized board. And it is proved that I check the Gerber file of the eval board shown in figure 2. But as you see, the DGND ground plane is isolated and don't connect to the AGND within a low impedance path on the PCB.

So should I connect the DGND and AGND together on the PCB? If it need to be seperated, should I place an isolated ground plane for DGND? 

2、 I have measured the AD9954's pin 14 and 22 with Multimeter and surprised to see that there is 60 ohms between those AGND pin. Is it right? Or dose it mean my AD9954 has borken down?

 figure 1.

figure 2.

  • 0
    •  Analog Employees 
    on Nov 28, 2019 8:06 AM

    Hi,

    I measured AD9954's pin 14 and 22 that is mounted on the evaluation board and obtained only 0.6ohms of impedance. With this, AGND and DGND could be connected together but if possible, it is recommended that these grounds be separated.

    Best regards,

    Mark