LMX2594PSEVM: simultaneous output

Renan,

You definitely can have both outputs operating at the same time.  For the EVM software, ensure that both outputs are powered up and OUTB_PD=0.  I say this because the default setup has OUTB_PD=1.  Is this the issue?

Regards,
Dean

Hello Dean,

Thank you for this response. Unfortunately, we program both devices OUTA_PD = 0 and OUTB_PD = 1, which should power up only OUTA outputs. This should be ok, since only OUTA is conected to output SMA connector. Yet still only OUTA of the LMX A produces signal at its output.

Any other solution we can offer?

Regards,

Renan

Hi Renan,

There are two synthesizers but only one SPI interface, we could only program one synthesizer at a time. For example, to program U1, S1 should be ON. Make sure the LED is lit after programming. 

Hello Noel,

Good day. We followed this procedure but only one of the outputs can be active at once.
Firstly I program the LMX2594 1 via uWire Switches then turn them off, then I turn on the swithches for the second LMx2594 and program it, once i program the second one the LMX2594 loses output signal. Can both outputs be active simultaneously?

Regards,
Renan

Hi Renan

Which one loss output after programming LMX2594 #2, are both LED lit?

Hi Renan,

I just tried this in the lab, I could get outputs from the synthesizers. 

One thing to note.

When you program it the first time after Vcc power up, if it does not lock, program R0 again or program all registers again, it should lock. 

Hello Noel,

Please see response from our customer:

I have tried it your way after Vcc power up Iprogram the both devices via TicsPro, neither lock, only RFout1 produces signal at the output, then I try and program both devices again and nothing changes.

Bellow are the Default Tics Pro settings that I am using, the only difference is that I use a 10MHZ reference clock which should be ok, since the minimum required is 5MHz.

Regards,

Renan

Hi Renan,

Is the 10MHz clock sine wave? What is the voltage swing?

Hello Noel,

please see attached screen capture of the refrence signal.

Can this be consider as suspect faulty hardware. I have used LMX2594 before where we developed our own hardware, we used the same reference signal as in the screen capture image and we had no problem with frequency lock. I have also used the same refrence signal with LMX2572 synthesizer, where we also did have any problems.

Regards,

Renan

Hi Renan,

Your clock does not have 50% duty cycle while you have enabled the input doubler in LMX2594.

Could you improve the duty cycle or try not use the doubler?

Hello Noel,

I tried not using the doubler and I het signals on both LMX2594 but the out put frequency is always 1.5x of what I set in TicksPro.

Regards,

Renan

Hi Renan,

I have no idea what went wrong. Could you do one last trial, use an external 100MHz reference clock, 10dBm, see if you can make it lock?