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LMH1983: Lock time

Shoo Saga
Expert 3336 points

Part Number: LMH1983

Hi team,

My customer mentioned It takes over 30 sec to lock PLL after TOF alignment. Is this normal behavior ?

attached the customer settings.

LMH1983 settings.xlsx

  • 0
    TI__Guru** 117340 points

    Hi Saga-san,

    I think so, datasheet has the following description.

  • 0 in reply to Noel Fung
    TI__Expert 3336 points

    Hi Fung-san,

    After they changed the initialization process, the lock time get shorter.

    the initialization process is below

    1.power up

    2. software reset: 0x05 [7] = 0b1

    3.switch settings change:0x09 [3:0] = 0010’b→ADDR 0x09 [3:0] = 0000’b(initialization process in old version datasheet )

    4.TOF Alignment mode settings change:0x13 [5:4] = 10’b→Wait 500ms (More than 2 frame period)→ADDR 0x13 [5:4] = 11’b(initialization process in current version datasheet )

    Before adding software reset
    　Set power off/on 20 times and measure lock time for each time.
    　　Lock time less than 10 seconds: 16 times
    　　　　　　　10 to 20 seconds: 1 time
    　　　　　　　From 20 seconds: 3 times

     After adding software reset
     Set power off/on 30 times, and measure lock time for each time.
    　　　Lock time 10 seconds or less: 30 times

    What is the reason issuing software reset after power up make the lock time shorter?

    Regards,

    Shoo

  • 0 in reply to Shoo Saga
    TI__Guru** 117340 points

    Hi Saga-san,

    I am not sure, there is no mentioning of power-on-reset circuitry in the datasheet. maybe a soft reset returns all registers to a known state and that improves the lock time.