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LMKDB1108: CLOCK BUFFER

SHEKHA SHOUKATH
Intellectual 510 points
Part Number: LMKDB1108

Tool/software:

Hi,

(a)

 in LMKDB1108's datasheet default value of OE register is not mentioned.

pins 14,19,30,34 have dual functionality (OE/ SBI), in order to use OE functionality SBI_EN (pin 11) has to be low.

but then SBI functionality is disabled then how SBI mode, SM bus mode and OE mode is enabled in order to use 8 output clocks.

in section 8.3.3.3, it is mentioned that all 3 modes has to be enabled, also in section 8.3.2.2 it is mentioned that outputs are enabled without any glitch (assuming register OE and SBI OE are active).

(b) 

in section 6.5, under electrical characteristics as per the below the image two jitter values specified foe PCIe 5 common clock:

under what conditions slew rate become 3.5V/ns and1.5V/ns

(c)

in the above images different jitter values are specified.

what is the actual jitter value of LMKDB1108?

(d)

what is the function of SBI mask register?

if sbi mode enabled what all registers will it use?

(e)

in the case of slew rate selection pin, only high specifies fast slew rate and low specifies slow slew rate .

what are the values for fast and slow slew rate.?

(f)

automatic output disable bit is enabled in default state, does this mean if the DUT doesn't receive valid clock input no output clock will be generated?

Thanks and Regards,

Shekha Shoukath

  • 0
    TI__Expert 8750 points

    Hi Shekha,

    SHEKHA SHOUKATH said:
    but then SBI functionality is disabled then how SBI mode, SM bus mode and OE mode is enabled in order to use 8 output clocks.

    If SBI mode is disabled, the OE pins and SMBus dictate the OE functionality. If you do not use SBI mode or SMBus, you can simply use the OE pins to control the outputs.

    SHEKHA SHOUKATH said:
    under what conditions slew rate become 3.5V/ns and1.5V/ns

    The input slew rates in these cases were varied, but the output slew rate of the LMKDB1108 is configurable through SLEWRATE_SEL.

    SHEKHA SHOUKATH said:
    what is the actual jitter value of LMKDB1108?

    The additive jitter value is dependent upon the input frequency and input slew rate. The typical additive jitter for a 100MHz signal with a 12kHz-20MHz BW and a 3.5V/ns slew rate is 27.3 fs.

    SHEKHA SHOUKATH said:

    what is the function of SBI mask register?

    if sbi mode enabled what all registers will it use?

    The SBI mask register allows you to read to and write from the respective SBI clocks with easier register writes - rather than having to write one by one to the respective registers. If SBI mode is enabled, it uses all of the registers listed in the datasheet - it just allows for a different method of interfacing.

    SHEKHA SHOUKATH said:
    what are the values for fast and slow slew rate.?

    The values for fast and slow slew rate are dependent upon the load you drive with the outputs. 

    SHEKHA SHOUKATH said:
    automatic output disable bit is enabled in default state, does this mean if the DUT doesn't receive valid clock input no output clock will be generated?

    This is correct.

    Thanks,

    Michael