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LMK61E07: Sample C code

HEEJAE JIN
Prodigy 30 points
Part Number: LMK61E07
Other Parts Discussed in Thread: LMK61E2, LMK62A2-100M

HI.

I want to control LMK61E07 using AVR.

I want to output 100MHz LVDS.

Can I get an I2C C code example?

Thanks.

  • 0
    TI__Expert 6140 points

    Hello, 

    May I ask why LMK61E07 was chosen? Is this due to 25 ppm stability vs 50 ppm of LMK61E2? 

    There's fixed frequency option (LMK61A2-100M00) that already provides 100 MHz LVDS, datasheet link: https://www.ti.com/lit/ds/symlink/lmk61a2-644m.pdf?ts=1645117761057&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLMK61A2-644M. This is also 50 ppm part. 

    There's also LMK62A2-100M fixed frequency device, 100 MHz LVDS, 50 ppm but even smaller package 5 x 3.2, datasheet link here: https://www.ti.com/lit/ds/symlink/lmk62a2-100m.pdf?ts=1645116847855&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLMK62A2-100M 

    So if 50 ppm will suffice there are multiple fixed frequency options available that don't require any re-programming. 

    LMK61E2 has a programming tool on its page that would apply here, however there are some manual modifications we need to make (re-programming register R24).

    Let me know whether the fixed frequency options can work and if not then we can discuss details of the programming. 

    Also, with regards to "C code" I'm not sure what that means... we can provide specific register programming needed to produce 100 MHz LVDS, and from there if you need to program that configuration into EEPROM so that device always starts up with 100 MHz LVDS. 

    Regards,

    Amin  

  • 0 in reply to Amin Eshraghi
    Prodigy 30 points

    Hello,

    Thanks for your reply.

    I am trying to use the LVDS output frequency by changing it from 10MHz to 800MHz without fixing it.

    I would like to know how to set the registers if I want to set it to 100MHz.

    I am currently able to communicate with I2C registers using the AVR.

    If you tell me how to set 100MHz, I will use it while varying from 10MHz to 800MHz for reference.

    Thanks.

  • 0 in reply to HEEJAE JIN
    TI__Expert 6140 points

    Hello, 

    Is 25 ppm needed or not? 

    LMK61E2 is programmable (8 pin package) and the programming tool is online. Here's the link to the product page: https://www.ti.com/product/LMK61E2?keyMatch=LMK61E2&tisearch=search-everything&usecase=GPN#software-development

    Scroll down and select software development: 

     

    The same software can be used to program LMK61E07. 

    This will provide register programming. Use the EZ config page and input frequency, output type and click generate configuration - you will the device get programmed to request condition. 

    It depends on the frequencies that you want to step through, for example if changing between 100 MHz and 200 MHz, more than likely it'll be the same VCO frequency and you would simply update the output divider to accommodate both - this would be a 1 register write / change with no requirement for VCO reset to recalibrate. 

    If you want to step through 100 MHz and 122.88 MHz, this will require a new VCO frequency, so generated config will have a few things different. 

    In either scenario, the configuration generated by the GUI will support the specific request you gave it. 

    Regards,

    Amin