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LMK61E08: Technical issues

Zhonghui Xu
Expert 5445 points
Part Number: LMK61E08
Other Parts Discussed in Thread: LMK61E07, LMK61E2, USB2ANY, LMK61E0M

Hi team,

I use LMK61E08,How to achieve 500MHz oscillation with amplitude between 0V and 0.8V?

Thank you very much for your help.

Best regards,

  • 0
    TI__Expert 6140 points

    Hello, 

    So intend is to reprogram the device. Just out of curiosity, why was LMK61E08 chosen and not LMK61E07 or LMK61E2? 

    You will need to change the VCO frequency to 5000 and the output divider value to 10 to get the correct frequency. 

    1. VCO freq to 5 GHz - update PLL N divider

    • PLL N divider Integer: R25 to 00h, R26 to C8h
    • PLL N divider fractional numerator: R27, R28, R29 all to 00h
    • PLL N divider fractional denominator: R30, R31, R32 all to 00h 

    2. Output divider update to 10

    • Program R22 to 00h 
    • Program R23 to 0Ah 

    3. Toggle VCO reset to recalibrate 

    • R72[1] =1, will self clear to 0 

    So xtal frequency = 50 MHz; no change to multiplier or divider: 50 * 2 / 4 = 25 MHz fpd. 25 * 200 (N divider) = 5, 5 GHz VCO. 5 GH / 10 (output divider) = 500 MHz. 

    LVDS and LVPECL can work at 500 MHz, review the output swing section as well as define whether that is the single ended swing or differential swing. Then you can program register R21 accordingly. 

    Regards,

    Amin 

  • 0 in reply to Amin Eshraghi
    TI__Expert 5445 points

    Hi Amin,

    If I change to LMK61E07 , what is the usage? Can I get the result I want? 

    I just want to get 500MHZ, the amplitude is between 0V and 0.8V, which product should I choose? Thank you

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Expert 6140 points

    Hi Zhonghui,

    LMK61E07 and LMK61E08 are only different in their start up EEPROM configuration. For your purposes, you need to reprogram anyway, so it's irrelevant. I was just curious if there was a thought process in choosing one over the other.

    The instructions I've provided work for LMK61E08 in changing the configuration to your desired frequency (on LMK61E07 they would be slightly different). And the comment on output format remains the same.

    Regards,

    Amin

  • 0 in reply to Amin Eshraghi
    TI__Expert 5445 points

    Hi Amin,

    Thanks for your reply, but I don’t know much about the reprogramming of LMK61E08, such as how to program R25 to 00h, R26 to C8h, etc.

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Mastermind 28550 points

    Hello Zhonghui,

    Have you designed a PCB with the LMK61E08 on it?  You can use the LMK61E2 profile in LMK61xx Oscillator Programming Tool to connect to the device, design your configuration and then program it.  This does require a USB2ANY.

    If you do not have a USB2ANY, you can still use the LMK61xx Oscillator Programming Tool to generate your configuration in "Demo Mode", then press the Program EEPROM.  The necessary register programming sequence is displayed in the status window at the bottom left of the GUI.  However to get the proper register programming easily, this info is in a log file (log.txt) located in: C:\Program Files (x86)\Texas Instruments\LMK61xx Oscillator Programming Tool

    You may consider deleting the log txt file before pressing the Program EEPROM button, this will make it easier to open this text file to have the register programming sequence that you can then write to the device.  It is suggested to poll for the NVMBUSY == 0 in the R49[2] position after R49 bit 0 and 1 are set for programming.  This appears to be: the 0x3153 write.  note 0x31 == R49 and 0x53 is the write to start the EEPROM programming.
      -- Note when the USB2ANY is writing, each write is a separate USB transaction so it is slow.

    So here is an example cut from the end of the log file:

    Wrote Register R0x35 as 0x3500
    Wrote Register R0x38 as 0x3800
    Wrote Register R0x48 as 0x4802
    Write all register complete
    Done writing all registers, about to commit registers to EEPROM
    Wrote Register R0x31 as 0x3150
    Wrote Register R0x38 as 0x38BE     ; Unlock EEPROM for write.  To write, next register write must set the NVMERASE and NVMPROG bits in R0x31 (R49).
    Wrote Register R0x31 as 0x3153      ; This must immediately follow 0x38BE.

    ;; Poll for busy bit here.


    Wrote Register R0x38 as 0x3800      ; This re-locks the EEPROM.
    Wrote Register R0x31 as 0x3150
    Wrote Register R0x31 as 0x3110
    EEPROM Programmed

    Hopefully this helps with how to program the LMK61E08 eeprom to the needed settings.

    73,
    Timothy

  • 0 in reply to Timothy T
    TI__Expert 5445 points

    Hi team,

    Thank you for your help.

    How do I program the register R21 if the single-ended swing is between 0V and 0.8V? Thanks.

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Expert 6140 points

    Hi Zhonghui, 

    Closest is probably LVPECL, making sure it's AC coupled and has the 150 ohm resistor. At 500 MHz I'm not sure if you'll get exactly 0.8V maximum, it might be closer to the lower end of 0.7V. 

    Regards,

    Amin

  • 0 in reply to Amin Eshraghi
    TI__Expert 5445 points

    Hi Amin,

    Thank you for your reply.

    Sorry, maybe my way of expression is not good. What I mean is, how much should I program the value of R21 to get the amplitude between 0V and 0.8V? Thank you!

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Expert 6140 points

    Hi Zhonghui, 

    You should program to LVPECL. I've put snapshots from the datasheet of everything you need, to know the value that must be programmed. 

    So R21[1:0] should be programmed 01b. R21 [6:2] is reserved. And R21[7] should be programmed to 0, a 1 would put the output buffer in power down. 

    Regards,

    Amin

  • 0 in reply to Amin Eshraghi
    TI__Expert 5445 points

    Hi Amin,

    Thank you very much for your reply, but after reading the programming procedures required for LMK61E08, it seems to exceed the equipment and tools I have. Do you have any services to help customers program? Can I place an order for a small amount of LMK61E08, such as 6 sets, and program the 500MHZ I want before shipment, and the voltage amplitude is between 0V~0.8V? It is convenient for me to complete my engineering design. Of course, programming services can be charged separately. Do you think it is feasible?

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Expert 5445 points

    Hi Amin,

    Is there any update?

    Thanks a lot.

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Mastermind 20900 points

    Hi Zhonghui,

    please allow some time until Amin answers due to Thanksgiving.

    I don't understand your request. What equipment and tools are not enough to program the LMK61E08? A simple usb to I2C device would be sufficient to execute the commands that Timothy and Amin posted earlier.

    Regards,

    Julian

  • 0 in reply to Julian Hagedorn
    TI__Expert 5445 points

    Hi team,

    Thank you for your reply of Julian.

    I also want to see Amin's analysis.

    Thanks,

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Expert 6140 points

    Hi Zhonghui, 

    I would defer to Julian on this front. As he mentioned it is only a simple usb to I2C device to execute the programming. 

    We typically do not support individual programming configurations post release of a product. 

    Regards,

    Amin 

  • 0 in reply to Amin Eshraghi
    TI__Expert 5445 points

    Hi Amin,

    Understood, in addition, how do I obtain the Program tool of LMK61E08 mentioned last time,
    Is it delivered with the product? Or do I have to purchase C:\Program Files (x86)\Texas Instruments\LMK61xx Oscillator Programming Tool separately?
    Thank you.

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Expert 6140 points

    Hi Zhonghui, 

    Like a software programming tool? So I provided instructions for direct register writes, those can be followed to update the registers accordingly. 

    If you're looking for software/GUI that takes inputs and updates the registers, I have a TICSpro profile that can be manually loaded (this is not released on the web). It is very similar to the LMK61xx Oscillator Programming Tool that you mention. 

    Regards,

    Amin

  • 0 in reply to Amin Eshraghi
    TI__Expert 5445 points

    Hi Amin,

    How long is the delivery time? Thanks!

    Does the oscillator products have a single-ended output of 500MHZ, 0V to 0.8V? Thank you!

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Expert 6140 points

    Hi Zhonghui, 

    There's no physical equipment to ship - I can post the software here that can help with programming, but again I provided direct register writes. The register configuration of the device needs to be updated to get it to configuration that you're requiring. 

    You need I2C adapter to program or you can use whatever controller you normally for I2C communication. Is that what's the hangup here? 

    Also, we've been over the 500 MHz 0 - 0.8V question, I'm not sure what I'm not addressing. Are you clear on output type? Are you clear on the type of swings that are provided with each output type? 

    Is it clear that there is no direct register programing and get x amount swing? 

    We've been going over this so I'm not sure what part is not coming out clear since the question is just being repeated. 

    Regards,

    Amin 

  • 0 in reply to Amin Eshraghi
    TI__Expert 5445 points

    Hi Amin,

    I'm very sorry, but I didn't notice that the oscillator I wanted was a single-ended output instead of a differential output. What I want is 500MHZ single-ended output, 0V~0.8V. Thank you for your patience reply.

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Expert 6140 points

    Hi Zhonghui, 

    The only LVCMOS oscillator we have available currently is LMK61E0M - https://www.ti.com/product/LMK61E0M

    Unfortunately this doesn't support 500 MHz. That is a quite a high frequency for LVCMOS, generally speaking we've only seen CMOS type signals top out at 200 MHz. What is load that's being driven? Why such a high frequency is required? 

    Or is the application capable of using a single ended signal from a differential type output like LVPECL or LVDS? LVPECL would meet provide similar type swing requriements, you would still need to terminate the other line to prevent reflections. 

    Also, LVCMOS generally is rail to rail swing, so 0 - 0.8V implying a 0.8V swing is not a typical LVCMOS type signal. Even 1.8V LVCMOS provides higher swing than that. 

    Regards,

    Amin 

  • 0 in reply to Amin Eshraghi
    TI__Expert 5445 points

    Hi Amin,

    "Because the designer of our company only asked me to buy an oscillator with a signal to GND 500MHZ, 0V~0.8V. As for what to drive, there is not much to say. As for the method of using differential to achieve single-ended, you can suggest using expensive Which of the company's differential oscillator products can achieve the 500MHZ, 0V~0.8V output of the single-ended oscillator I want? Thank you very much for your patient reply."

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Expert 5445 points

    Hi Amin,

    Is there any update?

    Thanks a lot.

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Expert 6140 points

    HI Zhonghui, 

    So my answers are still valid and nothing has changed. 

    CMOS single ended is rail to rail. So if you're looking for something in the 0 ~ 0.8V range exactly, there's nothing we can offer. The device I suggested above, is 3.3V LVCMOS but it also does not support 500 MHz, as CMOS degrades significantly at higher frequencies. In reality, there are no CMOS drivers at 500 MHz for XO. 

    The only other option is to use a differential XO and use it single ended. This is not something that we test or provide, as the device is differential. But this is the only option that would be available at 500 MHz and getting something in that range. My best recommendation is to use the differential part, DC couple and terminate the channel not being used. DC couple and provide the right loading on the P side of the channel with intention to use and then connect to O-scope. But again I can't comment on drive capability if your designer doesn't know what they're driving either. 

    Regards,

    Amin 

  • 0 in reply to Amin Eshraghi
    TI__Expert 5445 points

    Hi Amin,

    Yesterday our company’s RD told me that I hope that the oscillator frequency can be adjusted between 100~500MHZ, and the same is single-ended output 0V~0.8V. Currently I am looking for whether it is possible to use a differential to single-ended output circuit. Thank you very much you.

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Expert 6140 points

    Hi Zhongui, 

    Yes, the oscillator is programmable in terms of the output frequency. Some changes may just be an output divider update, but other's might require a new VCO frequency, which means more programming and a reset for VCO to calibrate. 

    The 0V ~ 0.8V, LVPECL is the best option. That is not programmable. 

    Regards,

    Amin