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LMK04821EVM: unlocked issue analysis

Adrian Liu
Intellectual 1250 points
Part Number: LMK04821EVM

Hi Team,

In customer use case, CLKIN=40MHz,OSCin=30.72MHz, PLL2 VCO=2000MHz, I meet some problems when setting this configuration.

LMK04821EVM cannot lock under the following configuration, please help with it, thank you.

in40 ocsin30_72 out1000 unlock.txt 
R0 (INIT)	0x000090
R0	0x000010
R2	0x000200
R3	0x000306
R4	0x0004D0
R5	0x00055B
R6	0x000600
R12	0x000C51
R13	0x000D04
R256	0x010002
R257	0x010155
R258	0x010255
R259	0x010301
R260	0x010402
R261	0x010500
R262	0x0106F1
R263	0x010755
R264	0x010802
R265	0x010955
R266	0x010A55
R267	0x010B00
R268	0x010C02
R269	0x010D00
R270	0x010EF1
R271	0x010F55
R272	0x011019
R273	0x011155
R274	0x011255
R275	0x011300
R276	0x011402
R277	0x011500
R278	0x0116F1
R279	0x011711
R280	0x011819
R281	0x011955
R282	0x011A55
R283	0x011B00
R284	0x011C02
R285	0x011D00
R286	0x011EF1
R287	0x011F11
R288	0x012019
R289	0x012155
R290	0x012255
R291	0x012300
R292	0x012402
R293	0x012500
R294	0x0126F1
R295	0x012711
R296	0x012819
R297	0x012955
R298	0x012A55
R299	0x012B00
R300	0x012C02
R301	0x012D00
R302	0x012EF1
R303	0x012F11
R304	0x013019
R305	0x013155
R306	0x013255
R307	0x013300
R308	0x013402
R309	0x013500
R310	0x0136F1
R311	0x013733
R312	0x013804
R313	0x013900
R314	0x013A01
R315	0x013B00
R316	0x013C00
R317	0x013D08
R318	0x013E03
R319	0x013F00
R320	0x01402F
R321	0x014100
R322	0x014200
R323	0x014311
R324	0x0144CB
R325	0x01457F
R326	0x014618
R327	0x01471A
R328	0x014802
R329	0x014942
R330	0x014A02
R331	0x014B16
R332	0x014C00
R333	0x014D00
R334	0x014EC0
R335	0x014F7F
R336	0x015003
R337	0x015102
R338	0x015200
R339	0x015300
R340	0x01547D
R341	0x015500
R342	0x01567D
R343	0x015700
R344	0x015896
R345	0x015900
R346	0x015A60
R347	0x015BD4
R348	0x015C20
R349	0x015D00
R350	0x015E00
R351	0x015F0B
R352	0x016000
R353	0x0161C0
R354	0x0162A4
R355	0x016300
R356	0x016400
R357	0x01650C
R369	0x0171AA
R370	0x017202
R371	0x017300
R372	0x017400
R380	0x017C15
R381	0x017D33
R358	0x016600
R359	0x016709
R360	0x0168C4
R361	0x016959
R362	0x016A20
R363	0x016B00
R364	0x016C00
R365	0x016D00
R366	0x016E13
R8189	0x1FFD00
R8190	0x1FFE00
R8191	0x1FFF53

BR

Adrian

  • 0
    TI__Genius 10975 points

    Hello Adrian,

    After importing your hex file with your specified values (assuming both CLKin0 and CLKin1 are 40MHz), there seems to be no problem on the frequency planning on my end. Therefore, I'm assuming there's a problem with your loop filter. Could you send me your topology and values you implemented for its components? Also, if possible, next time please attach the .tcs file, it makes it easier for me to debug. Please look at the picture below that shows where you click to save a .tcs file from TICS Pro.

    Thanks,

    Andrea

  • 0 in reply to Andrea Vallenilla
    TI__Intellectual 1250 points

    Hi Andrea,

                     Thanks for your reply. For the question you mentioned above,

                      (1) Customer did not change the topology of loop filter on EVM board. The topology and values are the default setting in the user guide as below.

                      (2) The .tcs file for the configuration is attached below, in this configuration, we can't config the EVB to locked. Please check

    clkin40 oscin3072 clkout1000 unlock-2.tcs

    Thanks 

    Adrian

  • 0 in reply to Adrian Liu
    TI__Genius 10975 points

    Hello Adrian,

    I will get back to you later. 

    Thanks,

    Andrea

  • 0 in reply to Andrea Vallenilla
    TI__Genius 10975 points

    Hello Adrian,

    The VCXO that you are using, is it the one on the board or are you using another one? If so, how did you include that VCXO to the board, i.e did you solder it into the EVM, do you have a separate board for the VCXO?

    I would like to note that if you are using the VCXO that comes already assembled into to EVM then your OSCin frequency has to be 122.88 MHz. To make the board assembled VCXO lock, it needs to receive a 122.88 MHz input, which is not the case based on your config. Why do you need a 30.72 MHz OSCin signal?

    Thanks,

    Andrea