LMX2594: several questions about LMX2594

David Zhao

Intellectual 1820 points

Part Number: LMX2594
Other Parts Discussed in Thread: TIDA-01410

My customer has several questions about LMX2594. Please help. Thanks!

What is the single-ended output power range of LMX2594?
For differential and single ended output, except for phase difference, any performance difference about phase noise and spur?
When adopting LMX2594 to work at 7.8-8.2G or 9.8G output, any half IF concern? Does customer need to add filter for half IF?

Regards

David

over 8 years ago

0 Simon Damphousse over 8 years ago

TI__Expert 5370 points

Hello David,

Please find my answers below:

1. What is the single-ended output power range of LMX2594?

This is the power as a function of frequency. Power adjustment is about 13 dB.

2. About differential and single ended output, except for phase difference, any performance difference about phase noise and spur?

By combining the two signals together (with a 180deg hybrid), there is the possibility to obtain more power however the PN and spurs will remain the same.

3. When adopting LMX2594 to work at 7.8-8.2G and 9.8G, any half IF concern? Does customer need to add filter for half IF?

The frequency mentioned above are direct VCO frequency and hence the ½ harmonic or fundamental feedthrough found with doubler architecture it NOT on LMX2594. ½ IF is another problem related to the performance of the mixer with respect to the 2x2 spur. I assume you are not referring this this issue.

Regards, Simon.

0 David Zhao over 8 years ago in reply to Simon Damphousse

TI__Intellectual 1820 points

Hi Simon

Thanks for feedback!

About the first question, power adjustment is about 13dB, then what is min and max power value of single-ended output? Thanks!

Regards
David

0 David Zhao over 8 years ago in reply to David Zhao

TI__Intellectual 1820 points

Hi Simon

Also LMX2594 datasheet I have in hand doesn't have package information inside. Could you help share LMX2594 package information including height? Thanks!

Regards

David

0 Dean Banerjee over 8 years ago in reply to David Zhao

TI__Mastermind 28001 points

David,

Figure 5 in the datasheet shows the output power as a function of frequency around 8 GHz, it is about +10 dBm with an inductor pull-up and +5 dBm with a resistor pull-up both for an OUTA_PWR setting of 50, which gives the maximum power. So if you change this setting from OUTA_PWR=50 to OUTA_PWR=0, a 13 dB drop would take it down from about +10 to -3 with inductor pull-up.

The output power is specific to the evaluation to the PCB and this is based on our measurements on our PCB.

Regards,
Dean

0 David Zhao over 8 years ago in reply to Dean Banerjee

TI__Intellectual 1820 points

1. The output power is for single-ended output or differential?

2. The test point is at the LMX2594 SMA output point?

Regards

David

0 Dean Banerjee over 8 years ago in reply to David Zhao

TI__Mastermind 28001 points

David,

The output power reported is Single-Ended and is what we believe is at the pin of the part.

To get these graphs, we used a board with the shortest possible trace (used reference design TIDA-01410) that was routed for single-ended outputs. The measured loss due to the board and cables was about 1 dB, so the number in this graph is about 1 dB higher than what we measured at the SMA connector for this board.

For the regular EVM, which is routed for differential output, the measured output power is a few dBm lower.

Regards,
Dean

0 Simon Damphousse over 8 years ago in reply to Dean Banerjee

TI__Expert 5370 points

Dear David, have we answered all your question? regards, Simon.

0 David Zhao over 8 years ago in reply to Simon Damphousse

TI__Intellectual 1820 points

Hi Simon

Yes. Thanks for your support!

Regards
David

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LMX2594: several questions about LMX2594