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Original question:

TRF3722: Enquiry About like This IC

TRF3722: loss of LOCK DETECT

Nir Flysher
Expert 3367 points
Part Number: TRF3722


Dear Team,

My customer is using the TRF3722IRGZR.

Its LD pin is set to LOCK DETECT by the software in register 6

The device outputs the expected frequency and power correctly.

Despite this, every 250 nsec the device reports a loss of lock for a short time and is locked again by toggling the LD pin.

See a transparent photo on the LD leg, voltage 1v per slot, time 100nsec per slot.

We tried to change values in registers related to lock sensitivity, without success.

 

Can anyone on the team advise what might be the issue ?

Regards,

Nir.

  • 0
    TI__Guru* 79334 points

    Hello,

    I would first recommend to slow down the calibration clock to the slowest clock possible during initial configuration and calibration of the VCO. By slowing down the cal clock, the VCO control voltage will go through a slower calibration loop, and increase the stability of the calibration. The calibration point is reference with the lock detector to detect the lock process.

    Please advise if you can adjust the following registers. I would recommend to 

    1. set bit 24 = 0 to decrease sensitivity

    2. please configure bit20/19 in various combinations is 00/01/10/11 testing to see which one eliminates the tail end. If it is the end of PFD comparison that gives more sensitive pulse, the useage of L/L, H/L may desensitize the end of PFD comparison to the reference.