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Hello Sir/Madam,

I am using ADL5380 eval board for same RF/LO Frequency. I have Given both the Input signals through Splitter for synchronizing the input signals. With the guidance of this forum i have bypassed the output side baluns to pass DC value and at R7x and  R6x i have populated a resistor of 500 ohms.  Do you have any data of what should be the IP, IN, QP and QN data for same Input frequency?

According to the datasheet, the impedance of single ended output is 25 ohms and oscilloscope which i am using has an impedance of 50 ohms. So do i have to  use impedance matching circuit between Eval Board and oscilloscope?

Also when i bypass the balun, the circuit becomes differential so can i terminate the port IN and QN port with 50 ohm termination?

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  • Hi Ankita,

    Is the supply current stable when you have an RF signal applied? Do you also have the LO signal applied? Are you able to get good results with both RF and LO it applied?

    I'm not sure what we would expect with RF signal off. I think we would consider it an in-determinant state and it's possible that it sits at a particular bias due to it's previous state and/or the LO applied.

    Best Regards,


  • Hi,

    Thank you David for the prompt response.

    No, the supply current keeps changing from 170 mA to 210mA 

    Yes, I have applied Lo signal of -3 dbm 

    The VOltage across VI i.e across R7 keeps changing according to different length cables at RF but voltage acrossR6 is same for all the conditions.

  • Hi Ankita,

    It sounds like the chip may be damaged. Please replace the chip and see if the results are the same.

    Also, please post a detailed schematic or block diagram of your configuration and setup for review.

    Best Regards,


  • Hi David,

    Below is the block diagram of the integrated setup  

    what should be the supply current after integrating with Instrumentation amplifier?

    Actually I checked with the new evaluation board, without integration with instrumentation amplifier, the supply current is 224mA and with integration with Instrumentation amplifier the supply current is 290 mA.

    Is it fine?

    Below i am attaching the changes we made in the eval board according to our application:

  • Hi Ankita,

    It is not clear from the attached schematic the changes you have made. What is R2 to R5? Are there any other changes?

    Please take the schematic and markup using red the changes you have made to the ADL5380 eval board, as well as a detailed schematic for the instrumentation amplifiers. This will make it easier to see the full picture of the implementation.

    Once the full picture is available, then each portion can be appropriately compartmentalized/simplified and analyzed by itself to ensure each is behaving well. Also, be sure to run an analysis/simulation of the instrumentation amplifiers to ensure they are working you expect.

    Best Regards,


  • Hi David,

    1. R2 to R5 is 0 Ohm.

    2. I am attaching the file below with the changes done in Eval board.

    Changes are as follows:

    Removed Resistor R13, R14, R15, R16, R17, R18 to bypass T2 and T4 and Populated 0 ohm resistor at R2 to R5.

    Also, I replaced the chip, without integrating with the Instrumentation Amplifier, the idle current is 188mA to 195mA (NOT STABLE) and by integrating the current is 245mA TO 270mA. 

    Below i am attaching the photo of integrated circuit.

    Please suggest if I am wrong.

    Thank you.

  • Hi Ankita,

    Support for this forum thread has been shifted to local FAE, who has reached out to you. Please continue working with him for troubleshooting and further questions.



  • Hi David,

    I need your help.

    I am testing the new Eval board of ADL 5380 .

    I have done all the necessary changes  told by you for the operating frequency 5.81Ghz at Lo and Rf like

    1. Removed R13 to R16

    2. Populated R2 to R5 with 0 ohm

    3. Populated R6 and R7 with 500 ohm

    Idle current is 230 mA

    I am attaching the photo of block diagram and Readings

    My question is according to the cable length( which we are using for phase change since we don’t  have phase shifter) 

    why only the I voltage is varying and not the Q voltage?

    Thank you