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Getting the ADL5380 to work

Category: Hardware

Hello,

We want to run it in single ended mode, we have 2.4 GHz carrier and RF signal going to the LOP port and RFP port, respectively.

The LON and RFN ports, as per the data sheet, are terminated with a 100 pF capacitor and the IP and QP signals are taken and fed into an LNA. We supplied 5VDC to VPOS and connected its respective ground to GND and GND1 on the eval board. When we look at the I and Q signals, its pretty much just noise near 0V. We also tried toggling the enable switch and in both positions got the same result.

The data sheet says that the eval board is configured for single ended output (p.34), but doesn't mention anything about the output impedance. From page 3, it says these pins have an output impedance of 25 ohms per pin. Also on p.34 (T2x, T4x), there is a description which includes the TCM9-1, which states "converts a differential high impedance IF output to a single-ended output. When loaded with 50 Ω, this balun presents a 450 Ω load to the device." So I'm confused as to whether I need to have a matching network if connecting to a LNA with 50 ohm input.

Another questions is regarding the 25 ohm single ended input impedance of the RFIP and LOIP (as shown in Figure 84 oh p. 25). Is the eval board "configured" to interface with a 50 ohms?

Any help is greatly appreciated.

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  • Hi Jitokazu, 

    You can use a 50ohm single ended RF, LO input and a 50ohm single ended baseband output with our eval board. Please refer to the attached schematic of our eval board for the same. I understand you're not seeing any output with our ADL5380 along with the LNA you have. I would recommend checking our part without the LNA. 

    Let me know if you still have questions after going through the datasheet, attached eval board schematic and testing ADL5380 eval board.

    Also, May i know what's the frequency of the baseband output you're trying to measure? I am a bit confused as you said both the LO and RF are 2.4GHz as this leads to DC output. 

    PDF

  • Hi,

    We are trying to use this part to obtain a baseband output at DC (1-10Hz). It wasn't clear from the datasheet if it'll work at DC. I managed to get the board working at higher frequencies (with and without an LNA at the output). Can you confirm if this will work at DC? If not, are there any other parts which will do this?

    Thx.

  • Yes, the ADL5380 will work at DC when RF Frequency = LO Frequency. Care must be taken to present adequate load impedance. For these low frequencies you will want to remove transformer and go direct into a 450 ohm differential load resistor, with no series capacitors.

  • Thanks! Will try this out this week and post results.