LMK04828: Custom LMK Not able to Configure in Distribution Mode

KLN

Part Number: LMK04828
Other Parts Discussed in Thread: USB2ANY

We have a board with LMK04828 and is configured via 3-wire SPI through external wires(length-0.5m). We are not able to see the Output on DCLK's / SDCLK's.

DCLK -5MHz

SDCLK-5MHz

Any way we can read back from SPI configuration or through status LED?

LMK is to be configured in Distribution Mode through CLKIN1-100MHz single ended Sine wave input i.e., 1.89Vpp (9dBm) and CLKIN0 is left unconnected.

The attached below schematic and config file for reference.

CLKIN1 circuit. CLKIN0 left open. CLKIN1 - AC Coupled sine wave (9dBm)

LMK config file:

Fullscreen Config_clock_module .txt Download

R0 (INIT)	0x000090
R0	0x000004
R2	0x000200
R3	0x000306
R4	0x0004D0
R5	0x00055B
R6	0x000600
R12	0x000C51
R13	0x000D04
R256	0x010001
R257	0x010155
R258	0x010255
R259	0x010301
R260	0x010422
R261	0x010500
R262	0x010670
R263	0x010755
R264	0x010861
R265	0x010955
R266	0x010A55
R267	0x010BB1
R268	0x010C22
R269	0x010D00
R270	0x010E78
R271	0x010F11
R272	0x011061
R273	0x011155
R274	0x011255
R275	0x0113B1
R276	0x011422
R277	0x011500
R278	0x011678
R279	0x011733
R280	0x011861
R281	0x011955
R282	0x011A55
R283	0x011BB1
R284	0x011C22
R285	0x011D00
R286	0x011E79
R287	0x011F53
R288	0x01206A
R289	0x012155
R290	0x012255
R291	0x0123B1
R292	0x012422
R293	0x012500
R294	0x012678
R295	0x012755
R296	0x012801
R297	0x012955
R298	0x012A55
R299	0x012B00
R300	0x012C02
R301	0x012D00
R302	0x012EF9
R303	0x012F05
R304	0x013016
R305	0x013155
R306	0x013255
R307	0x013300
R308	0x013402
R309	0x013500
R310	0x0136F9
R311	0x013700
R312	0x013845
R313	0x013903
R314	0x013A00
R315	0x013B14
R316	0x013C00
R317	0x013D0E
R318	0x013E03
R319	0x013F05
R320	0x0140F9
R321	0x014100
R322	0x014200
R323	0x014321
R324	0x0144FF
R325	0x01457F
R326	0x014618
R327	0x014702
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	0x015464
R341	0x015500
R342	0x0156C5
R343	0x015700
R344	0x015896
R345	0x015900
R346	0x015A64
R347	0x015BD0
R348	0x015C20
R349	0x015D00
R350	0x015E00
R351	0x015F0B
R352	0x016000
R353	0x016105
R354	0x016205
R355	0x016300
R356	0x016400
R357	0x01650C
R369	0x0171AA
R370	0x017202
R380	0x017C15
R381	0x017D33
R358	0x016600
R359	0x016700
R360	0x016850
R361	0x016959
R362	0x016A20
R363	0x016B00
R364	0x016C00
R365	0x016D6D
R366	0x016E13
R371	0x017320
R386	0x018200
R387	0x018300
R388	0x018400
R389	0x018500
R392	0x018800
R393	0x018900
R394	0x018A00
R395	0x018B00
R8189	0x1FFD00
R8190	0x1FFE00
R8191	0x1FFF53

Please let us know where we are missing.

We have tried capturing the spi signals we do activities on data.

Thanks

over 2 years ago

0 Andrea Vallenilla over 2 years ago

TI__Genius 10995 points

Hello Lakshiminarayana,

1) When setting distribution mode, did you click on the "Set Distribution" button in the "Set Modes" tab?

2) What input termination is going into the LMK04828 (i.e LVDS, LVPECL, LVCMOS, single-ended, etc)?

Also, you can set the either STATUS_LD pins to serve as SPI readback. To configure in TICS Pro, follow the screenshot below:

Hope this helps!

Good Luck,

Andrea

0 KLN over 2 years ago in reply to Andrea Vallenilla

Intellectual 320 points

1.We have set it in distribution mode.

2.We are providing single ended sinewave input to the CLKIN1. AC Coupled.

The connections of SPI looks okay. we are still not. Please have a look once on schematic and txt file attached above, Let us know anything we are missing,

0 KLN over 2 years ago in reply to Andrea Vallenilla

Intellectual 320 points

We have tried from USB2Any Module,

The distribution mode(CLKIN1-100MHz) never worked and we have observed all the LMK Power rails it seems good (3.3V) and LDOBYP1 and LDOBYP2 observed 2.5V and 1.5V
We have tried with Dual PLL with external VCXO 100MHz, It locked once (PLL1 and PLL2) but output frequency observed different i.e., For the Output clock 100MHz, we observed 512MHz and harmonics.
We have observed SPI data transaction
It has not locked after that.

Please suggest anything to be checked or we are missing. Any suggestion for debug are welcome.

Thanks,

0 Andrea Vallenilla over 2 years ago in reply to KLN

TI__Genius 10995 points

Hello Lakshiminarayana,

Why did you not populate R67? That 49 Ω resistor is needed for a single-ended signal into the CLKin1 pin. Your output setup for LVPECL seems to be incorrect, as well. I suggest you follow the data sheet recommendations for your input and output terminations- (p. 104 and 105). I have also included screenshots below.

I set up my EVM board in the lab with your config and it worked perfectly. You should also look at the schematic for our EVM and compare the setup between them (here). I'm assuming it's the solution I suggested above since the differences lie on the schematic. Hope this helps!

Good luck,

Andrea

0 KLN over 2 years ago in reply to Andrea Vallenilla

Intellectual 320 points

Hi,

R67 50Ohm part is mounted while testing.

We once saw LMK getting configured. After that it never getting configured. All the voltage are fine

0 Andrea Vallenilla over 2 years ago in reply to KLN

TI__Genius 10995 points

Hello Lakshiminarayana,

Andrea Vallenilla said:
Your output setup for LVPECL seems to be incorrect, as well. I suggest you follow the data sheet recommendations for your input and output terminations- (p. 104 and 105). I have also included screenshots below.

As mentioned previously, your output terminations do not seem to match those from the data sheet, why do you have 50 Ω resistors to ground after the 100 nF capacitors? I would suggest removing this resistor and trying it again. I have tried your config file on my board and it worked perfectly!

Thanks,

Andrea

0 KLN over 2 years ago in reply to Andrea Vallenilla

Intellectual 320 points

Hi Andrea Vallenilla

With the SPI wire length reduced we are able to configure with USB2Any.

Thanks for your suggestions.

0 KLN over 2 years ago in reply to Andrea Vallenilla

Intellectual 320 points

Hi Andrea Vallenilla

I've one more question on CLKIN_Type Format related,

BIPOLAR OR MOS: Will these effect on LMK Output.

Suppose, For eg., Differential LVPECL Input, If i chose MOS Input and for Single ended Sine wave input If I Choose MOS Input type, Is it okay?

Any performance related dependies?

Thanks

0 Julian Hagedorn over 2 years ago in reply to KLN

TI__Mastermind 20900 points

Hi Lakshminarayana,

If you have a LVPECL input clock, then it is recommended to use bipolar input type with AC coupling. If you use MOS input type you need to make sure that the LVPECL signal is biased correctly, which may involve more components.

there is no performance degradation between MOS and Bipolar if the input signal is comparable in terms of swing, slew rate and frequency. If you compare a slow slew rate sine wave with a high edge rate LVPECL signal, you will see higher additive jitter (in distribution mode) with the sine wave signal.

regards,

Julian

0 KLN over 2 years ago in reply to Julian Hagedorn

Intellectual 320 points

Julian Hagedorn said:
If you compare a slow slew rate sine wave with a high edge rate LVPECL signal, you will see higher additive jitter (in distribution mode) with the sine wave signal.

Hi Julian Hagedorn

Can you be more specific or explain more on this?

0 Julian Hagedorn over 2 years ago in reply to KLN

TI__Mastermind 20900 points

Hi KLN

please have a look at this blog: https://e2e.ti.com/blogs_/b/analogwire/posts/how-to-measure-additive-jitter-of-a-clock-buffer

thanks

Julian

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LMK04828: Custom LMK Not able to Configure in Distribution Mode