LMX2820: instcal fails with no option but to cycle power to device

Hi Mike,

Can you let me know more on the used workaround, INSTCAL procedure and used frequencies for your setup?

Would be great, if you can share the configuration file used for INSTCAL. You can send me over email, we can take it offline and support quickly to get the details on it.

Ideally PLL unlock not the case using instcal and need to look on configuration.

Thanks!

Regards,

Ajeet Pal

how could you think it is resolved?  the instcal seems to be full of anomolies and problems with questionable results. See my related posts.  For part of it, my solution of cycling the power and doing it all again until it passes gets us partly down the road.  but as you can see, close in, instacal still fails.  Please advise on how to get better results.

Hi Mike,

I didn't get your response on above question and might have system closed the ticket as did not get response for a while.

Regarding to your query, I believe you are following the Instant calibration procedure mentioned below:

1. Open TICS Pro and select EVM default mode configuration
2. In User Controls page, check all Double Buffer bits
3. In PLL page, uncheck DBLR_CAL_EN in Instant calibration box
4. Vcc power up the EVM
5. Press Ctrl+L to program the EVM to lock to 6GHz
6. Set INSTCAL_EN = 1 in Instant calibration box
7. Type 5650 and then Enter in the VCO box (PLL_NUM, PLL_N and INSTCAL_PLL_NUM will be programmed automatically)
8. Uncheck FCAL_EN in the VCO calibration box
9. Check FCAL_EN
10. Uncheck FCAL_EN and wait for a while (VCO will lock to 5650 MHz)
11. Change VCO frequency, for example, type 5800 and then Enter in the VCO box (PLL_NUM, PLL_N and INSTCAL_PLL_NUM will be programmed automatically)
12. Click Calibrate VCO button (this will write R0 once, VCO will lock to 5800 MHz)
13. Change VCO frequency to 6200 MHz
14. Click Calibrate VCO button (this will write R0 once, VCO will lock to 6200 MHz)

Once, LMX2820 is calibrated for Instant cal, how are you measuring the lock time in transient mode of instrument?

It suppose to be in external trigger mode and capture the frequency settling data with lock detect pin of LMX2820.

Would be great, if you can share your used configuration file (TICS pro format) for required frequencies and can validate in our setup.

Thanks!

Regards,

Ajeet Pal

I sent you the register configuration file that we use in the first post.  Using the lock detect to determine if the PLL has settled to the correct frequency is inadaquate.  The frequency will still be off by hundreds of Khz.  We use a Keysight E5052B to measure when the frequency gets within 500Hz as  you see on the plots I also sent you.  The point of the post is the inconsistent results, which cannot be seen on an average spectrum analyzer or signal analyzer like the PXA.  We are measuring the from the trailing edge of the chip select on the write to R0 per the data sheet.  The lock detect output of the LMX2820 is only a good indicator that it is on it way to the correct frequency.  Maybe you have never looked closely enough at the frequency settling?  If you have, do you see the frequency dependent differences?  If you have looked close in, and do not see any difference in settling time as a function of the hop, please advise on how we can get your instcal working better.  Have you actually work with the device making use of the instcal?  you never did answer my question of how long "wait a while" specifically is.

Hi Mike,

Unfortunately, I didn't receive any email from your end. Could you send me again, I dropped you a message with my details.

Regarding your queries, there are various ways to trigger the E5052B to capture the transient response and through lock detect is the one option to see the frequency settling time. 

It seems, you are triggering instrument by frequency trigger, which in video triggering, please correct me if otherwise.

As mentioned above, if you are following the above procedure for instant cal, it will provide fast lock frequency using instant cal.

I have done the quick test on EVM with the below configuration file and further steps, LUT would generate and lock the PLL at 5650MHz, just after FCAL_EN -->0. and next frequencies shows the fast lock time. I have saved the plots for you but unfortunately my PC got restart and lost all data. I will share the reference plots by Monday after retest on EVM.

1. Load below config file

LMX2820_INSTCAL.tcs

2. update TICS pro with highlighted section

3. FCAL --> 0 --> 1--> 0 (LUT generates and lock the PLL at 5650MHz)

4. Now, change the frequency and click on "Calibrate VCO". See the settling time.

There can be frequency drift in the RFout based on reference frequency stability and may need to set the target frequency in instrument for exact frequency.

Please try the above again and see the performance.

Thanks!

Regards,

Ajeet Pal