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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?

  • Hi Ankita,

    • I responded to the other forum thread with some additional guidance for akshay92; please review.
    • You should connect the 500 ohm differential load impedance in place of R7x and R6x. No additional terminations are needed.
    • Also, be careful connecting the baseband outputs into a 50 ohm oscilloscope, because DC voltage will be present. Depending upon oscilloscope, you could exceed the maximum input limit. It's best to observe the baseband outputs with high impedance probes or a DMM, since it's a DC voltage.
    • For the LO/RF signals there will be no issue using 50 ohm impedance test equipment or oscilloscope with 50 ohm input setting.

    Best Regards,


  • Thank you Sir for the quick response.

    I have a doubt regarding outputs. When i am connecting the Ip and Qp to the oscilloscope ports and when i am switching ON the 5V supply only, the output voltage obtained is Ip = 1.7V and Qp= 1.84v. Can you explain me what exactly is this output??

  • Hi Ankita,

    • The importance is the DC voltage across the load resistor. As the phase changes it causes the output stage to pump current from one side of the diff pair to the other.
    • Attached is an example diagram for your application. Please try that setup or something similar for measuring the DC voltages across the resistors.
    • As noted in the other thread, you will need to remove the resistor on the ADJ pin for operation above 5GHz.
    • Also, please see this article regarding system phase error calibration when using the ADL5380. Depending upon the implementation and configuration, you may need to follow this guide once you have DC voltage vs phase data.

    Best Regards,


  • Ok, Thank you sir. 

    I tried integrating INA114 instrumentational amplifier with the ADL5380. 

    The same results are obtained as before. when I turned ON the DC supply, the Qp, Ip output of ADL580 was 2.5 V and when i turned ON the RF/LO there was no change in the output of ADL5380 which was 2.53 which was same when i turned on only the DC Supply.

    Sir, what is this resistor for at pin 19?

  • Hi Ankita,

    • I'm not sure why the DC voltage would be present when you turn off the device. There must be something still powered in your setup or there is some capacitance which has been charged.
    • Before connecting the instrumentation amplifier, try getting the ADL5380 working by itself. You should be able to verify functionality with a DMM and then sweeping the phase difference between the RF and LO paths.

    • Regarding pin 19, the pin descriptions in the datasheet state: "A resistor to VS that optimizes third-order intercept. For operation 5 GHz, RADJ = open. See the Circuit Description section for more details."
    • Leaving the resistor open on that pin will optimize the non-itineraries in the mixer for operation above 5GHz.

    Best Regards,


  • Ok Thank you sir. By implementing the changes suggested by you, i' ll get back o you.

  • Hello Sir,

    By testing the ADL5380 board individually, When i am switching ON the  DC supply and RF/LO is OFF, the Voltage across load resistor is 1.4V at I and Q.

    and when i am switching ON the RF/LO there is no change in the voltage across load resistor.

    As you suggested, i checked the voltage across each capacitor which seems to be 2v across C1,C13 ; C6,C3,C7,C8, C11, C9- 5V AND C4, C14 - 0.4V 

    Idle current of the device is 256mA.

    I am not able to understand why still there is a voltage across load resistor when i am turning ON the supply.

  • Also after 2 hours the idle current of the board is displaying 160 mA 

  • Sir,  what should be the Rf and Lo power range if my operating frequency is 5.81 Ghz? 

  • Hi Ankita,

    It seems as though the chip may be damaged because supply current has changed drastically and you are not getting good results.

    To proceed, my recommendation would be the following:

    1. Obtain a new evaluation board.
    2. Markup the attached schematic with your intended changes and post here for review.
    3. Also, post your intended measurement setup for review.
    4. If you perform voltage checks on the evaluation board, please markup the various points on the schematic for review.





  • Ok sir. But what could be the reason for the damage sir? Actually i was experiencing a severe shock on output ports but then i turned off the device immediately. And after an hour when i turned on the device the current was 160 mA 

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