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CDCE62002 - VCO Calibration

Kawai
Guru 19785 points

Other Parts Discussed in Thread: CDCE62002

Hi Team,

Could you please let me ask you about the VCO calibration ?

[Q1]
To activate VCO Calibration, you would write 1->0->1 to /PD bit or PLLRESET bit in Register2.
When toggling the bit, do you need some wait time ? How long do you need to stay at "0" ?

[Q2]
When using the GUI, you could activate VCO calibration by clicking "/PD Calibration" button on the left side of GUI window. What is the command that is written to the register in the background when clicking this button ? Is it following three commands ?

1) R3=0x01001802 (CALSELECT=0, /PD=1)
2) R3=0x01001002 (CALSELECT=0, /PD=0)
3) R3=0x01001802 (CALSELECT=0, /PD=1)

As our customer having trouble calibrating the VCO, we would like to make sure about the operation of the calibration through the GUI.

[Q3]
This is a similar question to Q1.
When toggling /PD "PIN", how long do you need for /PD pin to stay at logic low ?

Thanks and Best Regards,
Kawai

  • 0
    TI__Expert 5325 points

    Hello Kawai-san,

    I will check on your questions to the device and the GUI and reply here as soon as I can.

    Best regards,

    Patrick

  • 0 in reply to Patrick Kammermayer
    Guru 19785 points

    Hi Patrick-san,

    Thank you for your support.

    As our customer's mass production schedule is coming in a short time, your prompt response will be appreciated.

    Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Expert 5325 points

    Hello Kawai-san,

    regarding your questions:

    >>[Q1]
    >>To activate VCO Calibration, you would write 1->0->1 to /PD bit or PLLRESET bit in Register2.
    >>When toggling the bit, do you need some wait time ? How long do you need to stay at "0" ?
    The bits act as a "copy" of the external pin, so taking the transfer rate of the SPI into account you should handle it the same way as in [Q3] while considering the SPI timing parameters between accesses.
    >>[Q2]
    >>When using the GUI, you could activate VCO calibration by clicking "/PD Calibration" button
    >>on the left side of GUI window. What is the command that is written to the register in
    >>the background when clicking this button ? Is it following three commands ?
    >>1) R3=0x01001802 (CALSELECT=0, /PD=1)
    >>2) R3=0x01001002 (CALSELECT=0, /PD=0)
    >>3) R3=0x01001802 (CALSELECT=0, /PD=1)
    The behaviour of the button depends on the CALSELECT bit inside the device. Either we toggle the !PD bit (register 2, bit 7)  or PLLRESET (register 2, bit 20).


    >>As our customer having trouble calibrating the VCO, we would like to make sure
    >>about the operation of the calibration through the GUI.
    >>
    >>[Q3]
    >>This is a similar question to Q1.
    >>When toggling /PD "PIN", how long do you need for /PD pin to stay at logic low ?

    The low pulse should be at least in the hundreds of microseconds. Please also check with your customer that the driver can achieve the rise and fall times at the device input (trf<4ns).

    For general VCO calibration and startup, please crosscheck the calculation in the "Start-up Time Estimation" section depending on the customer application.


    Best regards,

    Patrick

  • 0 in reply to Patrick Kammermayer
    Guru 19785 points

    Hi Patrick-san,

    Thanks for the detail information. Regarding your answer, may I confirm my recognition below ?

    - The wait time for /PD pin and /PD bit to stay at "0 / Low" in 1->0->1 transition is few hundreds of us. So I would say 1ms wait time.

    - Behavior of the "/PD Calibration" button is 1->0->1 transition in /PD bit.
      "PLLRESET Calibration" button is 1->0->1 transition in PLLRESET bit.

    - "t_id" and "t_pfd" in datasheet P.36 "Table 21 Start-up Time Dependencies" is
          t_id = 1 / (REFIN frequency)
          t_pfd = 1 / (PFD frequency)
       So the delay time for 27MHz REFIN would be 607us.

    Thanks and Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Genius 10320 points

    [q1] the important change on the /PD bit is from 0->1, so as Patrick said the register programming time should be ok

    [q2] follow table 20 in the DS to ensure the CALSELECT, PLLRESET, and PD bits are set in the right combination for device calibration

    [q3] Patrick was referring to the Timing Requirements for the /PD pin as shown on page 15 of the DS. The calculations you referred to are for an estimation of startup time.

    Gabe

  • 0 in reply to Gabe Ayala
    Guru 19785 points

    Hi Gabe-san,

    Thank you for your reply.

    [Q1] I understood that CDCE62002 would need  hundreds of microseconds for  wait time at "0" to complete calibration 1->0->1 transition, am I correct ? As I needed to answer the minimum wait time for the customer, I had mentioned 1ms because hundreds of microseconds could be 200 to 900 us.

    [Q3] Yes, I understand you need to meet tr/tf < 4ns in the /PD timing requirements. I just wanted to make sure if my recognition of t_id and t_PFD were correct in the startup estimation time calculation.

    I am grateful for your help.

    Best Regards,
    Kawai