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LMX2492: Wait time after chip reset?

hien ho
Prodigy 10 points
Part Number: LMX2492
Other Parts Discussed in Thread: LMX2491

Is there a specific timing for LMX2492 after SWRST is set? How long should we wait until reset is done? After this do we need to proceed with clearing the SWRST bit? and then proceed with programming registers in descending order? 

No where in the LMX2491/LMX2492 document it mention this basic  procedure?

  • 0
    TI__Guru* 81250 points

    Hi Hien,

    The reset will be taken place immediately. 

    After a reset, you need to program all the register in descending order. As such, you will have a chance to program R2 with the reset bit = 0.

  • 0 in reply to Noel Fung
    Prodigy 10 points

    Hi Noel,

     So I want to be clear as a normal initialization procedures should be as follow:

    line 1: write (0x2, 4); //where write is define as (register, data)

    //no waiting? 

    line 2: write (0x2, 1);

    //no wait ? 

    line 3: write (0x64,0)

    line 4: write (0x63,0)

    ......

    line x: write(0x3,0)

    is this correct? or we need to move  line 2 (write #2 - clearing the swrst) to the end? 

  • 0 in reply to hien ho
    TI__Guru* 81250 points

    Hi Hien,

    here is a recommended programming sequence:

    1. Vcc power up

    2. write R2 = 0x205 (SWRST = 1)

    3. Program R39, R38, ...., R3, R2, R1, R0 (if you just want to setup the PLL but want to program the RAMP registers later, otherwise start the programming sequence from R141