LMK04828: Configuration of the outputs when start-up.

Pedro Luis Diaz Herce

Part Number: LMK04828
Other Parts Discussed in Thread: ADC34J45

Hello,

We are working in a design where LMK04828 is connected to an ADC (ADC34J45) and we need to know which the configuration of LMK4828 outputs is (i.e. disabled or enabled) when LMK04828 is powered on before being programmed.

ADC34J45 indicates that it is necessary to avoid CLK inputs from LMK4808 when ADC34J45 is powered off.

Therefore, if LMK4808 starts-up with all outputs disabled, then ADC34J45 would not be damaged although this was powered off.

Thanks in advance.

Best Regards,

Pedro

over 1 year ago

0 William Pfennigwerth over 1 year ago

TI__Expert 8421 points

Pedro,

I will look into this and get back to you by tomorrow.

Regards,
Will

0 William Pfennigwerth over 1 year ago in reply to William Pfennigwerth

TI__Expert 8421 points

Pedro,

The LMK04828 power on reset state has all the SDCLKout and DCLKout0/2/12 disabled. All other outputs will output a nominal frequency on startup.

Regards,

Will

0 Pedro Luis Diaz Herce over 1 year ago in reply to William Pfennigwerth

Prodigy 180 points

Hello William,

Thank you very much for your feedback.

I understand that when the LMK04828 is powered on, then the next clock outputs are only powered down by default (before programming):

- DCLKout0 / DCLKout2 / DCLKout12

- SDCLKout1 / SDCLKout3 / SDCLKout13

Is my understanding right?

Thanks in advance.

Best Regards,

Pedro

0 William Pfennigwerth over 1 year ago in reply to Pedro Luis Diaz Herce

TI__Expert 8421 points

Pedro,

Not quite. There are three registers that will effect the output of the SDCLKout_Y. It is logically equivalent to "SYSREF output enabled" = ~CLKoutX_Y_PD & SDCLKout_Y_PD & SDCLKout_Y_FMT. Because SDCLKout_Y_PD is default set to 0, all SDCLKout_Y should be powered off on startup. You are correct with the DCLKout_0/2/12 being disabled.

Regards,

Will

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LMK04828: Configuration of the outputs when start-up.