LMK00105: About a weak internal biasing on the CLKin

Toshiyuki

Mastermind 7075 points

Part Number: LMK00105

Hi,

Please let me know the value of input impedance on the CLKin. I'd like to estimate the measurement error for probing.

Best Regards,

Toshiyuki

over 7 years ago

0 Puneet Sareen over 7 years ago

TI__Expert 8865 points

Hello Toshiyuki-san,
worst case DC input impedance can be calculated from the IIL/IIH numbers in the datasheet (electrical table p# 7).
Best regards
Puneet

0 Toshiyuki over 7 years ago in reply to Puneet Sareen

Mastermind 7075 points

Hi Puneet san,

Thank you for the reply. Customer measured the CLKin pin and CLKin*, and showing below. Is the result as expected?

CLKin = 1.094V

CLKin* = 1.365V

*using Agilent 34410A with a setting of input impedance Hi-z > 10Gohm

Best Regards,

Toshiyuki

0 Puneet Sareen over 7 years ago in reply to Toshiyuki

TI__Expert 8865 points

Hi Toshiyuki-san
Let me confirm with the designer. Are they measuring the differential input impedance?
Best regards
Puneet

0 Toshiyuki over 7 years ago in reply to Puneet Sareen

Mastermind 7075 points

HI Puneet san,

They are measuring the differential input voltage. I think the input voltage for single-ended needs to be more than 0.6Vpp, because the offset voltage between CLKin and CLKin* is about 300mV. However, the datasheet says the min spec is 0.3Vpp. Is my understanding correct?

Best Regards,

Toshiyuki

0 Patrick Kammermayer over 7 years ago in reply to Toshiyuki

TI__Expert 5325 points

Hello Toshiyuki-san,
thanks for the feedback. We need to improve our wording for the condition and clarify this matter.
Should you AC-couple the input, you will need 600mV or more. In case when you apply DC signals and provide a fairly strong bias on CLKin* for the threshold, 300mV will be suffice.

Best regards,
Patrick

Clock & timing

Clock & timing forum

LMK00105: About a weak internal biasing on the CLKin