LMX2615EVM-CVAL: No locking of the VCO in default setting and no correct frequency output

Hello Jurgen,

I could not see your images, can you try re-attaching them.

One thing you can try after loading the configuration is toggling the FCAL_EN bit to re-calibrate the PLL. This may help reach the locks state.

Other debug steps could be:

-> Ensure that communication is working, try toggling POWERDOWN to see if it is working currectly.

-> Use an external 100 MHz signal to see if there is an lock.

Thanks,

Vibhu

Dear Vibhu

Thanks for your reply.

Attached you can find the setting in TICS Pro, as well as a printscreen of the spectrum analyser. As you can see I asked for 5 GHz, and the device outputs 3.77 GHz. Changing the frequency in small steps (let's say of a few 10 MHz) doesn't change the output frequency of the device. Even asking to generate 4.9; 4.8; 4.7; 4.6 or 4.5 GHz (or 7.5 GHz) doesn't have any impact. The output stays at 3.77 GHz. Each time I toggle the FCAL_EN and make sure no box is highlighted in red or orange.

Concerning your proposed steps:

- I toggled already a few times the FCAL_EN. Each time I implemented a change (switch freq, ...) I toggled this box, without any success.

- The power down check box works fine. After I toggled it and try to reload the registers the same output frequency appears (not 5 GHz, by 3.77 GHz).

- Communication should work normally, because the device clearly reacts on my commands 'dfr. the power down command), but not in a good manner. I separately measured the reference Pro, and it clearly puts out a 100 MHz signal.

Hopefully this helps.

Many thanks for your effort.

Best regards

Jurgen

Dear Vibhu

Thanks for your reply.

Attached you can find the setting in TICS Pro, as well as a printscreen of the spectrum analyser. As you can see I asked for 5 GHz, and the device outputs 3.77 GHz. Changing the frequency in small steps (let's say of a few 10 MHz) doesn't change the output frequency of the device. Even asking to generate 4.9; 4.8; 4.7; 4.6 or 4.5 GHz (or 7.5 GHz) doesn't have any impact. The output stays at 3.77 GHz. Each time I toggle the FCAL_EN and make sure no box is highlighted in red or orange.

Concerning your proposed steps:

- I toggled already a few times the FCAL_EN. Each time I implemented a change (switch freq, ...) I toggled this box, without any success.

- The power down check box works fine. After I toggled it and try to reload the registers the same output frequency appears (not 5 GHz, by 3.77 GHz).

- Communication should work normally, because the device clearly reacts on my commands 'dfr. the power down command), but not in a good manner. I separately measured the reference Pro, and it clearly puts out a 100 MHz signal.

Hopefully this helps.

Many thanks for your effort.

Best regards

Jurgen

Just for completeness I added a picture of the setup. The upper right SMA connector is connected to a 50 Ohm Dummy load. The left SMA goes to the spectrum analyser. The bottom SMA's are connected to the Reference Pro. The upper most left SMA goes to the power supply. I already try to change the spectrum analyser and dummy load connections, but without any success.

Best regards

Jurgen

Hi Jurgen,

Could you remove R32 (close to OSCin pins) and try again? 

I think we have forgotten to remove R32 in the BOM, since both OSCin pins have 50Ω shunt already.