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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 David,

    I have few doubts regarding the load resistor and regarding output at I and Q SMA PORTS.

    1. What should be the exact value for load resistor at R7x and R6x? Is it 200 ohms or 500 ohms?

    2. During the test of ADL5380, what we did was through DMM we measured the output value of I and Q across R6x and R7x ( 500 ohm resistor at each R6x and R7X) but we were unable to test across SMA connectors. 

    Please correct me if we are doing anything wrong?

    How is it possible to get the outputs at SMA ports?

  • Hi Ankita,

    • Yes, that's correct, the resistor should be between 200 and 500 ohms.
    • It is possible using SMA to BNC connections to use the SMA ports, but you would neglect the grounding on these cables and connect the center pin conductor of each cable to each input of the DMM.
    • It may be easier just to use DMM test probes or solder on small wires to the resistor and then use clip leads to connect to the DMM. Since it's DC, there will be no concern regarding inductance of the cables, clip leads, etc.
    • Another possibility is to use two DMM's for the I resistor and two for the Q resistor, connecting to the SMA ports. You would then measure the absolute voltage on each baseband output and subtract the voltages: IP - IN and QP - QN. This method would give you the voltage across the resistors.

    Best Regards,


  • Ok 

    Thanks David . Will try this and if need help will get back to you.

  • Hi David,

    I integrated Adl5380 with instrumentational amplifier to obtain single ended output.

    The problem which i am facing now is

    1. Current is fluctuating from 170 mA to 200 mA.

    2. When i am switching ON the bias voltage(RF is OFF) the output across R6 shows 750mV and Output across R7 is 0v

    According to my knowledge, the voltage across R6 and R7 at condition RF= Off should be 0.

    Correct me if i am wrong.

     Thank you in advance.

  • 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.