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ADL5811 connection with ADL5387

In our design, we need to use both ADL5811 and ADL5387 evaluation board. Firstly, we would like to use ADL5811 evaluation board to convert the measured signal to an intermediate frequency IF. Then this IF signal is mixed down to I and Q signal by ADL5387 evaluation board. Thus, we connect the IFOP port of ADL5811 to the RF port of ADL5387. Unfortunately, we found the issue for this connection. When we added the power supply to ADL5811 evaluation board, this caused the short path between the power supply and ground of the ADL5387 evaluation board. Would you please help us resolve this problem? Can we directly connect ADL5811 and ADL5387 together?

 

Thanks.

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  • Hi Jiwei Sun,

                         From you description of the issue it sounds like you removed  T1,C3 & C4 from the ADL5811 and T1, C11 & C10 from the ADL5387. Are you trying to DC couple these two devices? The ADL5811 has open collector outputs which are pulled up to the 5 V supply. So if the capacitors mentioned above are replaced with jumpers then the ADL5811 output is connected to ground via L1 & L2 on the ADL5387 EVB.

    I recommend reviewing the RF INPUT section on page 16, in the ADL5387 datasheet.

    These two devices are not compatible for DC coupling and must be AC coupled.

Reply

  • Hi Jiwei Sun,

                         From you description of the issue it sounds like you removed  T1,C3 & C4 from the ADL5811 and T1, C11 & C10 from the ADL5387. Are you trying to DC couple these two devices? The ADL5811 has open collector outputs which are pulled up to the 5 V supply. So if the capacitors mentioned above are replaced with jumpers then the ADL5811 output is connected to ground via L1 & L2 on the ADL5387 EVB.

    I recommend reviewing the RF INPUT section on page 16, in the ADL5387 datasheet.

    These two devices are not compatible for DC coupling and must be AC coupled.

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