LMX2594EVM: LMX2594 Output Power

Ilya Tepltisky

Part Number: LMX2594EVM
Other Parts Discussed in Thread: LMX2594

It states in LMX2594 datasheet on p.8 that single ended output power at 15GHz is +2 dBm (using resistor) and +7dBm (using inductor). We are getting -7dBm at 15GHz reading on spectrum analyzer. Cable and connector losses are about 2.5dB.

The frequency of signal is correct, the R44 value is 2C1FA3, this is the highest power I've seen. R45 value is 2DC8DF.

The kit has been modified to drive RFOutA deferentially, we are looking at P side. N side is terminated via 49.9 to the GND (after DC blocking cap).

Please explain what is going on, we are missing at least 7 dB.

over 5 years ago

0 Noel Fung over 5 years ago

TI__Guru** 108300 points

Hi Ilya,

Please check if this is a soldering issue. We've seen problems with the SMA connectors not being soldered properly.

0 Ilya Tepltisky over 5 years ago in reply to Noel Fung

Prodigy 50 points

It's not soldering issue.

0 Ilya Tepltisky over 5 years ago in reply to Ilya Tepltisky

Prodigy 50 points

Your termination topology and values seems to be wrong for this frequency

0 Noel Fung over 5 years ago in reply to Ilya Tepltisky

TI__Guru** 108300 points

Hi Ilya,

Here is a reference how we deal with the pull-up and termination, it shown 50Ω pull-up but works for inductor pull-up.

Please note the pull-up are placed very close to the pins. The 10nF capacitors are broadband capacitors from ATC.

The inductors we used for evaluation is a 1nH inductor from Toko LL1005-FH1N0S. This inductor is EOL, you may use any inductor with very high SRF. FYI, this inductor has a SRF of 13599MHz.

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LMX2594EVM: LMX2594 Output Power