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DS92LV2422 +DS92LV2421

eli
Guru 13485 points
Other Parts Discussed in Thread: DS92LV2422, DS92LV2421

I got the below question:

On several projects we use  DS92LV2422 (DESERIALIZER) and DS92LV2421

We have problem with DS92LV2422 while working with low frequency

When clock in for the device is 12MHz, the LOCK of the DESERIALIZER is off, occasionally  (i.e no pll lock)

The datasheet for the deserializer requires 10-75MHz clock

We tried to use LF_MOD and SSCG, with no success

Does this problem known? Is there a way to work with low frequency?

Please do your best for ASAP reply

 

  • 0
    Guru 13485 points

    Any Feedback????

  • 0 in reply to eli
    TI__Guru* 93670 points

    Hi Eli,

    I just noticed your post. It is my understanding that DS92LV2422 and DS92LV2421 are maintaining lock at high frequency but at low frequency occasionally we lose lock. 

    Could you please monitor DS92LV2422 CLKOUT phase when you are at high frequency vs low frequency. Please use CLKIN of DS92LV2421 to trigger the scope.

    Regards,,nasser

  • 0 in reply to Nasser Mohammadi
    Guru 13485 points

    Hi Nasser,

    As  described  they have problem with DS92LV2422 DS92LV2422 lose lock occasionally in low frequency

    Attached 3 pictures , 12Mhz, 24Mhz, 48Mz.

    Customer have no problem in 24MHz and 48MHz, but  have LOCK lose in 12MHz

     Note: The voltage level different because the VCC I/O different  (3.3V and 1.8V)

    B.regards

    Eli

  • 0 in reply to eli
    TI__Guru* 93670 points

    Hi Eli,

    I understand they can operate at high frequency but have problem at low frequency(12MHz).

    Channel link devices lose lock if there is bit error so it means at 12MHz we have some sources of noise that is causing us to get bit error but at higher frequency the noise is not within our bandwidth or is not as critical so this is not a problem. The first thing we have to do is to see if this is occuring on the Tx or Rx side?  Then we need to ask ourselves what are the potential sources of noise given higher frequency is working fine? The first thing that came to my mind is power supply switching frequency or in general power supply noise. Can we use a DC lab supply to see if we see a similar behavior? Or use bigger size Caps(i.e 10uF) right next to the device. Or maybe EMI or noise coupling of some sort is causing us this problem. Also, if you reduce the distance between Tx and Rx do you still see this problem at 12MHz? Maybe we are right on the boarder at 12MHz. The bottom line is that we have a noise source that is causing us bit error and we should devise a way to find the root cause and hopefully remedy this.

    Regards,,nasser