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DAC38RF82: External balun with TSW40RF82 EVM

Intellectual 555 points

Replies: 4

Views: 73

Part Number: DAC38RF82

Hello,

I am trying to use TCM2-33WX+ as it has a low phase and amplitude imbalance. 

On TSW40RF82EVM, I have made the following mods. 

1. populate L7, L8, R382 and R380.

2. remove R381 and R386. 

3. Connect J40  TCM2-33WX+ secondary pin 3. 

4. Connect J39 to TCM2-33WX+ secondary dot pin 4.

5. Output on primary

But my signal level is reduced by about 9 dB compared to the on the board balun. 

Do I need to populate R369? 

What should be the voltage at the point where R386 and L7 meet?

Please let me know.

Thank you.

Mallesh

  • Guru 65940 points

    Mallesh,

    Replace R382 and R380 with 0.1uF caps since the +1.8V_ANA reference supply needs to be AC coupled.

    Regards,

    Jim 

  • In reply to jim s:

    Jim,

    You are right.

    They need to be ac coupled. I did not see that. 

    Are there any other changes that need to be done?

    Please let me know. 

    It is a bit hard to do these changes as there is a shield.

    Thank you very much. 

    Mallesh

  • Guru 65940 points

    In reply to Channamallesh Hiremath:

    Mallesh,

    I think this is it.

    Regards,

    Jim

  • In reply to jim s:

    Jim,

    I could not get an external balun configuration working.

    The frequency response with external balun was awful. About 8 dB variation across the whole frequency band.

    Probably, I am using the wrong balun. I do not know. I have abandoned my experiment.

    I have gone back to the onboard balun.

    Thanks for your help.

    Mallesh

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