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Difference between LMH0040/1 and LMH0050/1

John Porter1
Intellectual 345 points
Other Parts Discussed in Thread: LMH0040, LMH0041, LMH0050, LMH0051

From customer: I would like to understand the differences in the part numbers for the same series of parts. It’s clear as mud in the datasheets.

My customer would like to understand the difference between the LMH0040,41,50, and 51 devices. In looking at the comparison table, it appears the primary difference between the devices is the input and output types supported. Not sure what the special features are? They are looking to do a HD broadcast video demo by plugging into their existing hardware solution.

  • 0
    TI__Mastermind 29655 points
    Hi John,

    The LMH0040 and LMH0050 are serializers from LVDS inputs to a single high-speed output. The LMH0041 and LMH0051 are deserializers from a single high-speed input to LVDS outputs.

    The big difference is the type of signaling used for the high-speed output (LMH0040/50) and input (LMH0041/51):

    LMH0040 and LMH0041 operate up to HD data rates (SMPTE292M at 1.485 Gbps), and the high-speed data path linking the two is intended for a 75-Ohm single-ended coaxial cable. This means that the cable driver (LMH0040) follows SMPTE driver standards such as required input return loss and output slew rates depending on the given data rate. If the plan is to interface with a 75-ohm coaxial cable, then your SerDes pair should be the LMH0040 and LMH0041.

    LMH0050 and LMH0051 have effectively the same SerDes function as the LMH0040 and LMH0041, operating up to HD data rates (SMPTE292M at 1.485 Gbps). However, the high-speed data path linking the two is intended for 100-ohm differential pair CML signaling. This is a different topology that does not require the same return loss and slew rate parameters that SMPTE requires for 75-ohm single-ened coaxial cabling. If the plan is to interface the high-speed signal with a twisted pair cable or twin-axial cable (100-ohm differential), the your SerDes pair should be the LMH0050 and LMH0051.

    Note that in the case of the LMH0040 and LMH0041, you will need to provide the required external caps, pull-up termination resistors, and return loss network. For the LMH0050 and LMH0051, the 100-ohm differential resistor across the positive and negative pair is internal. Although it is not in the application circuit, we strongly recommend using a 4.7 uF AC coupling cap to prevent creating an unwanted ground loop due to conflicting SerDes common voltage and ground references. Please refer to the application circuits in the datasheets for more details.

    Thanks,

    Michael