ADS5409 dual balun input

Eugene Volkov

Intellectual 410 points

Other Parts Discussed in Thread: ADS5402

Hello.

In my board i use dual balun ETC1-1-13 identical matching circuit as EVM board for ADS5402 EVM.

Impedance matched to the load 50, but I see that input signal level decreases by 6 dB.

What could be the cause of the fall of the input signal level?

over 8 years ago

0 jim s over 8 years ago

TI__Guru* 91947 points

Eugene,

Remove the last resistor to the right. I think it is R31 but not sure as I cannot read your schematic very well. This is a DNI on the TI EVM.

Regards,

Jim

0 Eugene Volkov over 8 years ago in reply to jim s

Intellectual 410 points

Thank you, Jim.

this 100 Om resistor not installed.

I add real shematic :

0 Richard Prentice over 8 years ago in reply to Eugene Volkov

TI__Mastermind 29220 points

Hi,

What is the frequency of the signal you are trying to pass through the baluns? Even within the passband of the baluns I would expect maybe a dB of loss through each balun, but if your frequency is towards the edge of the specified passband of the baluns then the loss would be higher.

Regards,

Richard P.

0 Eugene Volkov over 8 years ago in reply to Richard Prentice

Intellectual 410 points

I see the voltage drop for low frequencies - 10 - 100 МГц.

0 Richard Prentice over 8 years ago in reply to Eugene Volkov

TI__Mastermind 29220 points

Hi,

an input frequency of 100MHz should be fine for the passband of the balun. If you want to experiment with it, you could remove the AC coupling caps C3, C4 to disconnect the ADC from the input circuit, and solder a straight 50 ohm resistor across the first pads of the cap footprints, so that the balun sees a 50 ohm termination and nothing else. This would remove the loading of the ADC inputs and let you check the rest of the input circuit. Knowing what loss to expect up to that point, I would then reinstall the AC coupling caps and see what loss is found with the ADC analog inputs connected.

Regards,

Richard P.

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ADS5409 dual balun input