• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 21 subscribers
  • Views 480 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMX2572: In full assist mode, the LMX2572 occurs an exception at 85°C

HWA Zhao
Prodigy 40 points
Part Number: LMX2572

Hi,

In no assist mode, the LMX2572 can normally switch frequency and normal lock in the temperature range of -40 ° C ~ 85 ° C, and after half an hour of operation, re-power on, LMX2572 working state is also normal;

In Full assist mode, the LMX2572 can normally switch frequency and normal lock in the temperature range of -40 ° C ~ 60 ° C, and after half an hour of operation, re-power on, LMX2572 working state is also normal;

In Full assist mode, the LMX2572 is always energized, the ambient temperature is slowly increased from 25 °C to 80 °C, and then kept at 80 °C for two hours. From the temperature rise to the heat preservation process, the LMX2572 is always energized. After two hours, the frequency switching test was performed, and the LMX2572 can normally switch the frequency and lock normally. However, at 80 °C, the LMX2572 is powered off and re-powered, or the POWER DOWN of the configuration register R0 is set to 1, and then set to 0, the LMX2572 is in an unlocked state, and the output frequency is not controlled. -40 ° C ~ 60 ° C, according to the above operation of the LMX2572, the above abnormal conditions do not occur.

Question: In full assist mode, the LMX2572 is powered on again at 85°C, and an exception occurs. However, in no assist mode, is it normal? What register do I need to configure?

Kind regards,

Jonas

  • 0
    TI__Genius 16845 points

    Thanks for posting on E2E. I have assigned your post to the responsible engineer. He will respond to you soon.

    Kind regards,
    Lane

  • 0 in reply to Lane Boyd
    TI__Guru** 107450 points

    Hi Zhao,

    Were you using the three VCO parameters data that you have taken at 25C when you power up and program the part at 85C?

    Without assist, the VCO will calibrate everytime it is power up and programmed. As such, it will lock at different temperature. 

    In full assist mode, if you only have VCO parameters data at 25C and use them at any other temperatures, it may not lock at certain temperatures. 

    To correctly use full assist mode, you need to take VCO parameters data at different temperatures as well. So you will need a lookup table for different frequencies and temperatures.

  • 0 in reply to Noel Fung
    Prodigy 40 points

    Hi 

        Thanks for your reply .Yes, I was using the three VCO parameters data that I have taken at 25C when I power up and program the part at 85C.

    The problems are : 1. The environment is raised from 25 ° C to 85 ° C. As long as the device is always powered during the whole process, the frequency will not be lost and the frequency can be switched normally. If the device is powered back on, it will be lost. Why does the environment rise from 25 ° C to 85 ° C, as long as the device is powered on during the entire process, can it work normally?

    2. We have also tried to take three VCO parameters at 85 ° C without assist. Then in full assist mode, I used the three VCO parameters and program the part, the result is the part output frequency is not controlled and lost?

    Kind regards,

    Jonas

  • 0 in reply to HWA Zhao
    TI__Guru** 107450 points

    Hi Jonas,

    What were the three VCO parameters you've got at 25C and 85C?

    Here is my suggest procedure:

    1. At 25C, Vcc power up the part, program it to lock to, say 3GHz. 

    2. set MUXOUT_LD_SEL = 0 (readback mode)

    3. Read registers R110, R111 and R112

    4. Power down the part.

    5. repeat the above steps at 85C