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THS4552: Configure Single-ended input to Diffferential output for THS4552PWEVM

Phan Khai
Prodigy 10 points
Part Number: THS4552

Hi everybody,
I have one question about configuring the input and output of THS4552PWEVM (https://www.ti.com/tool/THS4552PWEVM )
I have read the THS4552PWEVM guideline. The THS4552PWEVM  board is designed for differential input to single-ended output.
However, My application is single-ended input to differential output singal with 1Mhz signal bandwidth.
How to configure the THS4552PWEVM board for my application?
My solution:
- At input: I terminate  the IN1+ by 50ohm resistive SMA load
- At output: I remove balun and R14, add  R1, R12=0 ohm, add SMA at OUT1 -
Could you please help me to solve this problem?
Thanks



  • +1
    TI__Mastermind 20927 points

    Hello Phan,

    Please see my summary solution below:

    At Input:

    • EVM is configured to be used with single or differential inputs; you do not need to change the input structure as the unused SMA connector already terminates the signal path into a 50 Ohm SMA load.  You can leave the input structure in the default configuration.

    At Output:

    • Remove balun
    • Install R11, R12 with zero-Ohm resistors
    • Remove R14 zero-Ohm to GND resistor
    • Install R16 zero-Ohm resistor to connect output of R12 to SMA
    • Install SMA connector at OUT1-

    You can transpose these steps onto the second signal chain if you need to do so.

    Best,

    Alec

  • 0 in reply to Alec Saebeler
    Prodigy 10 points

    Your answer is clear.
    Thank you very much.

  • 0 in reply to Alec Saebeler
    Prodigy 10 points

    Hi Alec, 

    I have one question about the output matching network.
    Because the default design THS4552PWEVM has an output at SMA_50 0hm impedance (OUT1+), 
    Balun resistance  with ratio 1:1  => Zout_diff = 50ohm
    When using differential output (remove balun) and no change in the matching network, Zout_diff is still equal to 50 0hm 
    => It is not good to match with the load SMA-50ohm

    What do you think about this problem?
    Thanks

  • +1 in reply to Phan Khai
    TI__Mastermind 26845 points

    Hello Phan, 

      For output matching network to 50 ohm instrument/load while also maintaining 1kOhm load to match with characterization data in the datasheet:

    1. Remove R9
    2. Add 52.3Ohm Resistors to R13 and R14

    Thank you,

    Sima 

  • +1 in reply to Sima Jalaleddine
    TI__Mastermind 20927 points

    Hello Phan,

    As a small addition to Sima's note: 

    1.  You can also opt to increase R9 to get 100 Ohms differential impedance seen by the test equipment; you would need to adjust R43 & R44 to maintain your same 1k load, as it would go up with an increased R9.

    2. You may also increase the 52.3 Ohm resistors to better match 100 Ohm load when used at R13, R14.  The current impedance viewed by the test equipment is around 94 Ohms, which is a bit low.

    Best,

    Alec

  • +1 in reply to Alec Saebeler
    Prodigy 10 points

    I think my problem is solved with your help

    Thank Alec and Sima,