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LMK04832: LMK04832 Distribution Mode

Colby Davis
Prodigy 20 points
Part Number: LMK04832

I am having trouble getting my LMK04832 configured in distribution mode. I have configured it with the latest TICS Pro (version 1.7.5.7) and have attached the register set that I'm using. Attempting to distribute a 122 MHz signal from CLKin1 to CLKout0. At CLKin1 the signal is single ended and AC coupled.

If I turn the signal on during configuration I am able to see it at the output for about 1 second before it disappears. I've confirmed that this is my signal by repeating the test with the input off during configuration -- output does not appear in this case. It seems like something is causing it to shut off after a second.

With that in mind I tried removing the writes to Registers 0x166-0x168 (PLL2_N), thinking maybe the PLL was calibrating and causing an issue. This didn't seem to change the behavior.

I also came across this forum post and enabled DCC as a result. Again did not help.

https://e2e.ti.com/support/clock-timing-group/clock-and-timing/f/clock-timing-forum/992784/lmk04832-lmk04832-distribution-mode-does-not-work

Any ideas what I might be missing?

Fullscreen lmk04832_cfg.txt Download 
R0 (INIT)	0x000090
R0	0x000010
R2	0x000200
R3	0x000306
R4	0x0004D1
R5	0x000563
R6	0x000650
R12	0x000C51
R13	0x000D04
R256	0x010001
R257	0x01010A
R258	0x010200
R259	0x010344
R260	0x010410
R261	0x010500
R262	0x010601
R263	0x010755
R264	0x010818
R265	0x01090A
R266	0x010A00
R267	0x010B40
R268	0x010C10
R269	0x010D00
R270	0x010E01
R271	0x010F05
R272	0x011018
R273	0x01110A
R274	0x011200
R275	0x011340
R276	0x011410
R277	0x011500
R278	0x011601
R279	0x011705
R280	0x011818
R281	0x01190A
R282	0x011A00
R283	0x011B40
R284	0x011C10
R285	0x011D00
R286	0x011E01
R287	0x011F05
R288	0x012008
R289	0x01210A
R290	0x012280
R291	0x012340
R292	0x012410
R293	0x012500
R294	0x012601
R295	0x012700
R296	0x012808
R297	0x01290A
R298	0x012A80
R299	0x012B40
R300	0x012C10
R301	0x012D00
R302	0x012E01
R303	0x012F00
R304	0x013002
R305	0x01310A
R306	0x013280
R307	0x013340
R308	0x013410
R309	0x013500
R310	0x013601
R311	0x013700
R312	0x013845
R313	0x013900
R314	0x013A0C
R315	0x013B00
R316	0x013C00
R317	0x013D08
R318	0x013E03
R319	0x013F00
R320	0x0140FF
R321	0x014100
R322	0x014200
R323	0x014301
R324	0x014400
R325	0x014500
R326	0x01461A
R327	0x014713
R328	0x014802
R329	0x014942
R330	0x014A03
R331	0x014B06
R332	0x014C00
R333	0x014D00
R334	0x014EC0
R335	0x014F7F
R336	0x015001
R337	0x015102
R338	0x015200
R339	0x015300
R340	0x015478
R341	0x015500
R342	0x015678
R343	0x015700
R344	0x015896
R345	0x015904
R346	0x015AB0
R347	0x015BD4
R348	0x015C20
R349	0x015D00
R350	0x015E1E
R351	0x015F0B
R352	0x016000
R353	0x016101
R354	0x01624C
R355	0x016300
R356	0x016400
R357	0x01650C
R361	0x016958
R362	0x016A20
R363	0x016B00
R364	0x016C00
R365	0x016D00
R366	0x016E13
R371	0x017370
R375	0x017700
R386	0x018200
R387	0x018300
R358	0x016604
R359	0x016700
R360	0x01680C
R1365	0x055500

  • 0
    TI__Guru** 108130 points

    Hi Colby,

    With AC-coupled single-ended input clock, you should set the buffer type to Bipolar.

  • 0 in reply to Noel Fung
    Prodigy 20 points

    Hi Noel,

    Thanks for the reply. Unfortunately changing the buffer type did not change the behavior.

  • 0 in reply to Colby Davis
    TI__Guru** 108130 points

    Hi Colby,

    I dumped your configuration to the EVM, changed the buffer to Bipolar, and I got output from CLKout0. 

    Did you configure the type of CLKout in hardware properly? For example, CLKout0 is LVPECL, do you have 150Ω shunt resistors?

  • 0
    Prodigy 20 points

    I traced this down to the OSCin_PD bit in register 0x140. When set to 1 (power down) this caused my CLKout0 output to be about 35 dB low. When set to 0 the CLKout0 is output as expected.

    I do have an oscillator connected to OSCin but am not using it for this configuration. Not sure why this seems to affect Distribution Mode. Verified that I am distributing CLKin1 by modifying the frequency on that input and seeing CLKout0 move.

    Here's the final configuration that works:

    R0 (INIT)   0x000090
R0          0x000010
R2          0x000200
R3          0x000306
R4          0x0004D1
R5          0x000563
R6          0x000650
R12         0x000C51
R13         0x000D04
R256        0x010001
R257        0x01010A
R258        0x010200
R259        0x010344
R260        0x010410
R261        0x010500
R262        0x010601
R263        0x010755
R264        0x010818
R265        0x01090A
R266        0x010A00
R267        0x010B40
R268        0x010C10
R269        0x010D00
R270        0x010E01
R271        0x010F05
R272        0x011018
R273        0x01110A
R274        0x011200
R275        0x011340
R276        0x011410
R277        0x011500
R278        0x011601
R279        0x011705
R280        0x011818
R281        0x01190A
R282        0x011A00
R283        0x011B40
R284        0x011C10
R285        0x011D00
R286        0x011E01
R287        0x011F05
R288        0x012008
R289        0x01210A
R290        0x012280
R291        0x012340
R292        0x012410
R293        0x012500
R294        0x012601
R295        0x012700
R296        0x012808
R297        0x01290A
R298        0x012A80
R299        0x012B40
R300        0x012C10
R301        0x012D00
R302        0x012E01
R303        0x012F00
R304        0x013002
R305        0x01310A
R306        0x013280
R307        0x013340
R308        0x013410
R309        0x013500
R310        0x013601
R311        0x013700
R312        0x013845
R313        0x013900
R314        0x013A0C
R315        0x013B00
R316        0x013C00
R317        0x013D08
R318        0x013E03
R319        0x013F00
R320        0x0140EF
R321        0x014100
R322        0x014200
R323        0x014301
R324        0x014400
R325        0x014500
R326        0x014618
R327        0x014713
R328        0x014802
R329        0x014942
R330        0x014A03
R331        0x014B06
R332        0x014C00
R333        0x014D00
R334        0x014EC0
R335        0x014F7F
R336        0x015001
R337        0x015102
R338        0x015200
R339        0x015300
R340        0x015478
R341        0x015500
R342        0x015678
R343        0x015700
R344        0x015896
R345        0x015904
R346        0x015AB0
R347        0x015BD4
R348        0x015C20
R349        0x015D00
R350        0x015E1E
R351        0x015F0B
R352        0x016000
R353        0x016101
R354        0x01624C
R355        0x016300
R356        0x016400
R357        0x01650C
R361        0x016958
R362        0x016A20
R363        0x016B00
R364        0x016C00
R365        0x016D00
R366        0x016E13
R371        0x017370
R375        0x017700
R386        0x018200
R387        0x018300
R358        0x016604
R359        0x016700
R360        0x01680C
R1365       0x055500

  • 0 in reply to Noel Fung
    Prodigy 20 points

    Sorry the comment above about the buffer type not making a difference is not quite right. I took a closer look at this -- changing buffer type did make some difference but did not completely solve the problem.

    With buffer type = MOS I got no visible output at all.

    Changing to bipolar allowed for some output, but it was about 35 dB down from expected.

  • 0 in reply to Colby Davis
    TI__Guru** 108130 points

    Hi Colby,

    Did you check your hardware? Make sure your hardware matches with your output buffer type configuration.