LMK00105: HCMOS input for LMK00105

Jan Budroweit

Part Number: LMK00105

Hi,

reading the datasheet of the LMK00105 it has been mentioned that the input inlcudes LVMCOS. However, my current application uses a HCMOS oscillator with a 3.3V supply voltage and a swing of 0.9*Vs max and 0.1*Vs min. Is this type of oscillator suitable or do i have to reduce the input voltage swing?

Thanks and regards

Jan

over 8 years ago

0 Puneet Sareen over 8 years ago

TI__Expert 8865 points

Hi Jan

Does that mean the clock input has VIH=0.9*VDD and VOL=0.1*VDD? if yes, then there should be no issue.

Best regards
Puneet

0 Jan Budroweit over 8 years ago in reply to Puneet Sareen

Prodigy 90 points

Hi Puneet,

the TCXO (Vectron tx-321 - vectron.com/.../tx-321.pdf) I'am using is specified with that signal levels. I was a little bit confused reading the datasheet of the LMK00105 which explains that the single-ended voltage swing shall be within 0.3 and 2 Volts. I that case this will be an issue, since the max swing of the oscillator will be 0.33 to 2.97 V. Probably is missunderstood something

Thanks
Jan

0 Puneet Sareen over 8 years ago in reply to Jan Budroweit

TI__Expert 8865 points

Hi Jan

Here is the explanation: as specified in the datasheet, the VIN can be as low as 0 and VIH can be as high as VDD. For the very high swing signals, the output duty cycle might degrade based on the input rise/fall times. If you apply the input swing within the specified limits (0.3-2V), this issue will not be there. So moving forward, I would recommended you to limit the swing within the specified limits.
Let me know if you need further support.

Best regards
Puneet

0 Jan Budroweit over 8 years ago in reply to Puneet Sareen

Prodigy 90 points

So the conclusion is that this oscillator with HCMOS signal in not recommended to use without limiting the swing ? As mentioned above, the specified output swing of the oscillator is something 0,33 to 2,97 which exceed the limitations

0 Jan Budroweit over 8 years ago in reply to Jan Budroweit

Prodigy 90 points

Puneet,

so could you verify my suggestions? Would you recommend NOT to used the suggest oscillator?
0,33V to 2,97V Vpp swing and a duty cycle of typ 50% (60% max)

0 Puneet Sareen over 8 years ago in reply to Jan Budroweit

TI__Expert 8865 points

Hello Jan

The device is characterized & tested for datasheet limits. The performance is guaranteed if you follow the spec limits. Although if you apply this signal to the device you will get 50% duty cycle with nominal units but specs are not guaranteed as the swing is outside the datasheet max limit.

Best regards
Puneet

0 Jan Budroweit over 8 years ago in reply to Puneet Sareen

Prodigy 90 points

Hi Puneet,

thanks, i guess i have found what i was looking for. The CDCLV1310 http://www.ti.com/lit/ds/symlink/cdclvc1310.pdf

0 Timothy T over 8 years ago in reply to Jan Budroweit

TI__Mastermind 28550 points

Note the input swing can be limited through a simple voltage divider.

Clock & timing

Clock & timing forum

LMK00105: HCMOS input for LMK00105