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LMK61E2: Register setting for 150MHz and 75MHz

Part Number: LMK61E2

Hi Team,

I used the TICS pro to set  the desired clk frequency(150MHz and 75MHz) and export the address and the data.

1. Could you help check below register value is correct or not

2. If I would like to do command in LMK61E2, I could only find out the register which is R/W and Write the below value to brand new LMK61E2, right?

75MHz:

R0 0x0010
R1 0x010B
R2 0x0233
R8 0x08B0
R9 0x0901
R16 0x1000
R17 0x1180
R21 0x1502
R22 0x1600
R23 0x1740
R25 0x1900
R26 0x1A30
R27 0x1B00
R28 0x1C00
R29 0x1D00
R30 0x1E00
R31 0x1F00
R32 0x2001
R33 0x210C
R34 0x2228
R35 0x2303
R36 0x2404
R37 0x2500
R38 0x2600
R39 0x2700
R47 0x2F00
R48 0x3000
R49 0x3110
R50 0x3200
R51 0x3300
R52 0x3400
R53 0x3500
R56 0x3800
R72 0x4802

150MHz

R0 0x0010
R1 0x010B
R2 0x0233
R8 0x08B0
R9 0x0901
R16 0x1000
R17 0x1180
R21 0x1502
R22 0x1600
R23 0x1720
R25 0x1900
R26 0x1A30
R27 0x1B00
R28 0x1C00
R29 0x1D00
R30 0x1E00
R31 0x1F00
R32 0x2001
R33 0x210C
R34 0x2228
R35 0x2303
R36 0x2404
R37 0x2500
R38 0x2600
R39 0x2700
R47 0x2F00
R48 0x3000
R49 0x3110
R50 0x3200
R51 0x3300
R52 0x3400
R53 0x3500
R56 0x3800
R72 0x4802

Thank you.

Regards,

Roy

  • Hi Team,

    Excuse me. Any one could help me?

    Regards,

    Roy

  • Hi Roy, 

    Was "generate configuration" used within TICSpro to generate the following register settings? Loading them into my GUI does show me the expected results of 75 MHz and 150 MHz. 

    From there you should need to do a file -> load to load the registers and that should give you the desired results. 

    Let me know if I misunderstood or didn't answer your questions properly. 

    Thansk and regards, Amin 

  • Hi Amin,

    I think that you have misunderstand in my question. I understand that the register that I attached could set LMK61E2 to achieve 75MHz and 150MHz clock.

    But  in the real design, we don't have TICSpro to generate desired clk, we should need I2C to write the register. But I'm not sure which register should be set. Now we have register address/data. So should I write all the register value in R/W register in my design? do they have sequence setting requirement?

    Thank you.

    Regards,

    Roy 

  • Hi Roy, 

    Thanks for clarifying, I understand now. And this is a good question, as all registers do not need to be written. For example R16 and R17 should never be updated, as those are device specific and trimmed accordingly to achieve the desired PPM. 

    I believe the VCO frequency is being updated from the EEPROM of the device since the different versions provide 156.25 and 125 MHz which are based off of 5000 MHz VCO, while your frequency planning is resulting in using 4800 MHz VCO. 

    These should be the registers needing to be updated: 

    - R25 and R26: updating PLL N-divider integer value 

    - R27, R28, and R29: updating PLL N-divider numerator

    - R30, R31, and R32: updating PLL N-divider denominator 

    - R22 and R23: updating output divider 

    - R21: updating output type - this would only be needed if you have LVPECL version and need LVDS (as your configs above show LVDS 0x02) 

    Important thing to note, a reset is required because VCO frequency is being updated, PLL needs to be reset to allow for re-calibration. R72[1] changed to 1 should reset device and allow re-calibration. This is a self clearing bit. 

    Lastly if you notice the only difference between your 2 configurations is R23, the output divider. Since all that's changing is, rather than dividing by 64 (4800/64 = 75 MHz) it's being divided by 32 (4800/32 = 150 MHz) to achieve different frequency. So to go from one to the other, only that register needs to be updated and no reset is required since VCO does not need to re-calibrate. But again this is only to go from one to the other, the initial update changing the VCO frequency needs to have occurred. 

    Thanks and regards,

    Amin 

  • Hi Amin,

    Thank you for your detailed comment. It's very helpful.

    One thing would like to check is VCO frequency. I see VCO value in LMK61E2 datasheet is 4.6GHz - 5.6GHz and the typical value is 5GHz.

    And I use R23 to generate my desired frequency but it have a little difference because VCO value isn't accurate. Is it right?

    Regards,

    Roy

  • Hi Roy, 

    I'm not sure I understand the question. The VCO range is 4.6 - 5.6 GHz. Depending on your desired output frequency, the VCO frequency changes. accordingly. The versions of LMK61E2 on the datasheet are: 

    Both 156.25 and 125 MHz use 5 GHz VCO frequency. 5 GHz / 32 (output divider) = 156.25 MHz. 5 GHz / 40 (output divider) = 125 MHz. At 5 GHz VCO other frequencies such as 312.5, 250, 500, 166.67 MHz... etc. can all be generated by simply updating the output divider (R22 and R23). 

    But your desired output frequencies are 75 and 150 MHz. Both of which require a 4.8 GHz VCO. Once device is locked at 4.8 GHz VCO, again different output dividers can be used to generate different frequencies. 

    Thank and regards, 

    Amin