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LMH1208: Consultation on LMH1208 Clock Restorer

Vayne Li
Intellectual 960 points
Part Number: LMH1208
Other Parts Discussed in Thread: LMH1228

Tool/software:

Hi Teams,

Excuse me, does LMH1208 require an external clock restorer?
If using LMH1228, the internal integrated clock restorer mentioned in the datasheet, does it not require clock devices on the outside and can output SDI directly

  • 0
    TI__Guru**** 176641 points

    Hi,

    The LMH1208 a continuous time linear equalizer (CTLE) block for IN0. The CTLE or EQ compensates for frequency-dependent loss due to the transmission media prior to the device input. The CTLE accomplishes this by applying variable gain to the input signal, thereby boosting higher frequencies more than lower frequencies. The CTLE block extends the signal bandwidth, restores the signal amplitude, and reduces ISI caused by the transmission medium. 

    The LMH1228 on-chip reclocker attenuates high-frequency jitter and fully regenerates the data using a clean, low-jitter clock. The reclocker has a built-in loop filter and does not require any input reference clock.  

    So both the LMH1208 and LMH1228 can output SDI directly. But LMH1208 can only reduce ISI, but not attenuates high frequency jitter. The LMH1228 can reduce ISI but also attenuates high frequency jitter.

    Thanks

    David 

  • 0 in reply to David (ASIC) Liu
    Intellectual 960 points

    Hi David,

    Thank you for your reply.

    Let me rephrase, the previous description may have been a bit inaccurate
    What I want to ask is whether LMH1208 without an internal locker means it needs to add such a device to the external circuit?
    Can LMH1228 output SDI without adding any external components

  • 0 in reply to Vayne Li
    TI__Guru**** 176641 points

    Hi,

    Please see my response below

    What I want to ask is whether LMH1208 without an internal locker means it needs to add such a device to the external circuit?

    The reclocker attenuates high-frequency jitter and fully regenerates the data using a clean, low-jitter clock. So with LMH1208, are you seeing excessive high frequency jitter with your system design? If you do, then you will need an external reclocker or LMH1228 to clean up the jitter. 

    Can LMH1228 output SDI without adding any external components

    LMH1228 can drive SDI directly without additional external components as shown in the example below.

    Thanks

    David