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LMK61E2-125M: LMK61E2BBA

Mezbah Shaber
Prodigy 20 points
Part Number: LMK61E2-125M
Other Parts Discussed in Thread: LMK61E2

Dear Colleague,
We tried to change the default clock frequency to 200Mhz by writing to EEPROM of LMK61E2BBA (default frequency on 125Mhz). But, after the power cycle, I2C communication is broken and LMK61 did not produce any frequency.

The sequence of register programming before the LMK61E2 died is tabulated below.

Register NUM New value Comment
21 02h LVDS activation
33 0Ch Dither disabled, Interger mode
34 28h Integer mode -> charge pump 6.4mA
36 04h R2 = 500 Ohm
38 00h  R3 = 18 Ohm
37 00h C1 = 5pF 
39 07h C3 = 0pF
35 07h enable 2nd order loop filter (tool)
27 00h PLL_NUM = 0
28 00h PLL_NUM = 0
29 00h PLL_NUM = 0
30 00h PLL_DEN = 1
31 00h PLL_DEN = 1
32 01h PLL_DEN = 1
Setting 200 Mhz clock 
72 02h reset
22 00h
23 1Ch
25 00h
26 38h
10 02h calibrate (*after reset*)
Now I tried to write this sequency to EEPROM of LMK61E2
56 BEh
49 01h (Note: instruction tells to change only R49.0)
but I accidentally changed the whole register to 01
56 00h
  • 0
    TI__Mastermind 28550 points
    Have you tried scanning the whole I2C bus to see if it responds at some other address?

    I think your missing step was to not write R49.6 = 1 to copy registers to SRAM before doing a programming the EEPROM. Also, you could try programming R49 = 0x03. This will do a NVMERASE and NVMPROGRAM at the same time (be sure to have written the SRAM first).

    73,
    Timothy