LMV225SDEVAL: repetitive DC offset on output voltage

Hi Houdali,

What are the output voltages you are seeing for the range of input power you are putting in?

What voltages are you applying to VDD and ENABLE?

Thanks,

David Chaparro

Hi,

The output voltage fits the datasheet curve with a offset voltage between 100mV and 175mV vs (Pin=-30dBm to -1dBm).

The Vdd and Enable voltage is 3V.

Thanks for supporting us.

Hi,

The offset is above what the datasheet curve shows.

Hi Houdali,

How are you producing the 868MHz signal? Are you connecting the signal directly to the evaluation board or is there something between them like an amplifier?

Regards,

David

Hi,

This is a pure 868MHz tone (no modulated signal). Yes, I connect the signal directly to the eval board.

Kind regards

Hi,

Were any additional components installed on the evaluation board?

Are you able to verify the exact power level of the signal you are sending? Would it be possible for you to try with a higher frequency input and verify that you are seeing the same offset?

Thanks,

David

Hi, 

Yes, I'm able to ckeck the signal level at RFIN with a spectrum analyzer and it's done. I already tried with a higher frequency of 2GHz gave that gave me the same DC voltage.

Hi,

What voltage do you read when there is no RF input?

Can you make sure that the 100pF coupling capacitor is installed on the EVM.

Regards,

David

Hi,

Yes there is a coupling capacitor but I can't know the value.

How about the output voltage when there is no signal present?

Without RF input signal, the DC ouptu is around 208mV

This is in line with the datasheet.

Can you check the DC output voltage near the logarithmic intercept (-45 to -43 dBm). The output voltage should be about 208mV. Also can you share the exact voltage you are seeing for the -30dBm and 0dBm levels.

Thanks,

David