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LMK1C1104A: question for the usage

Daisuke Nomura
Intellectual 1270 points

Part Number: LMK1C1104A

Customer is looking for a fast clock buffer that receives a 3.3V input signal and branches it to four 2.5V output signals. It's 25MHz and CMOS.  He found the "LMK1C1104A" on your website, and the datasheet states the following. I believe it will work under the above conditions, but I'd appreciate some advice on the following.

"Supply voltage: 3.3V, 2.5V, or 1.8V Fail-safe inputs: 3.3V tolerant input at all supply voltages."

1) Are there any problems with using it as a 3.3V to 2.5V level shifter as described above? (Just to be sure, let me confirm.)

2) Are there any precautions I should take when using it as a level shifter, or are there any recommended circuits? I'd appreciate your advice. (For example, if it's better to add a resistor to the clock input signal, or not use all four output ports fully, etc.)

3) We found a similar buffer with it called "LMK1C1104PWR." This differs from the LMK1C1104A in that it has an A after the number, but what is the difference? (From a quick look at the datasheet, it appears to have the same functionality.)

Could you answe it?

Thanks and best regards,

Daisuke Nomura

  • 0
    TI__Mastermind 32152 points

    Hello Daisuke, 
    The PW is the TSSOP package designator (leaded) inside the OPN. 
    A the designator is in the GPN which means Asynchronous. 
    Most buffer are synchronous but some usage cases such as 1PPS signals require asynchronous signaling to ensure they outputs go immediately low and don't finish the current period which is something synchronous buffers do. 

    Just this for a better understanding: 

    The devices are available in both TSSOP and WSON packages. 

    The PWR lettering in the OPN just refers to the TSSOP package. 

    You can level shift a 3.3V LVCMOS signal using LMK1C110x or LMK1C110xA depending on whet her you prefer synchronous or asynchronous buffering with a 2.5 VDD supply. 

    There shouldn't really be any precautions necessary when level shifting. Just ensure you follow the recommended operating conditions. 

    Best regards, 

    Vicente 

  • 0
    TI__Intellectual 1270 points

    Vincente-san,

    Thank you for your answer. Your explanation is helpful to proceed with customer device selection and design start.

    Thanks and best regards,

    Daisuke Nomura