LMK04828: External reference input

Purna Sindhuja

Part Number: LMK04828

Hi.. CLK104 board is having LMK04828B and on-board TCXO. I need to use the LMK with the external 10 MHz reference input. Although I am disabling TCXO and making necessary changes in TICS PRO, the device is taking reference from TCXO.. Please help me on how to resolve this issue.

over 3 years ago

0 Ajeet Pal over 3 years ago

TI__Genius 12560 points

Hi,

Can you please share the clocking board schematic to understand the architecture and will be able to suggest the solution?

Thanks!

Regards,

Ajeet Pal

0 Purna Sindhuja over 3 years ago in reply to Ajeet Pal

Prodigy 10 points

Hii Ajeet Pal..

I attached clocking board schematic, TICS pro configuration used and CLK104 user guide.

Also I anticipate my TICS pro settings.. Please verify it.

I got few doubts. 1) Is it advisable to turn off Hold over in manual mode, as I am not able to find whether board is clocking with external reference ? 2) How do settings for Pin select mode, as I did not find Logic High option for CLKin_SEL0_TYPE in TICS pro ?

Desired CLk freq : 400 MHz, SYSREF: 4 MHz, with 10 MHz external clk input, in Nested Zero Delay Dual loop mode.

Thanks & Regards,

Sindhu

..ticsproconfig.zip

0 Purna Sindhuja over 3 years ago in reply to Purna Sindhuja

Prodigy 10 points

SCHEMATIC.zip

0 Ajeet Pal over 3 years ago in reply to Purna Sindhuja

TI__Genius 12560 points

Hi,

Can you confirm by disabling the TCXO, PLL1 is locking? How you are ensure, that TCXO is generating the output in disabling mode?

I would be anticipating, that by disabling the TCXO, you may be seeing PLL2 lock but not PLL1.

However, by selecting the external reference 10MHz at CLKin0, select CLKin0_Type as "Bipolar", when feeding external single ended sine wave input.

Regarding your queries:

1. If you wants to select the CLKinX input manually, you can turn off the Holdover.

2. For Pin select mode follow the section 9.3.5.2 in datasheet.

Thanks!

Regards,
Ajeet Pal

0 Purna Sindhuja over 3 years ago in reply to Ajeet Pal

Prodigy 10 points

Hi Ajeet Pal,

I tested by disabling Clkin1 pin, as you said LED status is off, hence PLL1 is not locked.

Due to PLL2 Data converter tiles are getting ready. But I need the tiles not to get ready till I give external 10 MHz clock. So I disabled Holdover option. Then I am expecting PLL2 also remain in unlocked condition and tiles status - not ready. This is not happening. Is there something else I am missing ? I have attached register values for your reference.

What can be the minimum Feedback PD frequency ?

Thanks & Regards,

Sindhu

0 Ajeet Pal over 3 years ago in reply to Purna Sindhuja

TI__Genius 12560 points

Hi Sindhu,

You can try to operate in dual PLL nested zero delay mode, where PLL2 feedback goes to PLL1 and until it locks PLL1, it didn't lock PLL2 also.

Thanks!

Regards,

Ajeet Pal

0 Purna Sindhuja over 3 years ago in reply to Ajeet Pal

Prodigy 10 points

Hi Ajeet Pal,

I tested in the Dual loop 0 delay nested setup with SYSREF Feedback only. Plz check the register settings once.

Thanks & regards,

Sindhu

0 Purna Sindhuja over 3 years ago in reply to Purna Sindhuja

Prodigy 10 points

Hi Ajeet Pal,

I have tried all the possible ways I understood but no output. Could you please share any LMK04828B example file with the settings you are suggesting & external clk input on pin 0. I will test it.

How much PLL1_WND_SIZE do I need to set ?

Thanks & Regards,

Sindhu

0 Ajeet Pal over 3 years ago in reply to Purna Sindhuja

TI__Genius 12560 points

Hi Sindhu,

Sorry, dual PLL doesn't help here. As VCXO frequency is fixed and can be fine tune using the CPout1 input based on CLKinX input. Hence, PLL2 will always on as VCO frequency set. If you want to have output is not ready, you can power down the output till CLKin is not present and PLL1 will lock.

Thanks!

Regards,

Ajeet Pal

0 Purna Sindhuja over 3 years ago in reply to Ajeet Pal

Prodigy 10 points

Hi Ajeet Pal,

Ok understood. Thanks for the information.

Regards,

Sindhu

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LMK04828: External reference input