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LMH0397: Inquiry on LMH0397 Input Threshold Variations

Diego Shinji Kawaguchi
Prodigy 140 points
Part Number: LMH0397

Tool/software:

Dear Team,

 

I have a question regarding the 4-level input thresholds (L, R, F, H) for pins such as HOST_EQ0 and OUT_CTRL on the LMH0397.

Specifically, I would like to understand the extent of variation in the internal voltage thresholds under typical and extreme operating conditions, including the impact of temperature and manufacturing tolerances.

 

As background, we plan to change the pull-down resistor value from 20 kΩ to 22 kΩ.

Using the datasheet, I verified that the resulting voltage levels align with the specified thresholds for the desired logic levels.

However, I want to ensure that this resistor change remains safe when considering potential variations in internal resistance or threshold values.

 

Could you please confirm the expected range of variation for these thresholds?

 

Thank you for your assistance.

 

Best regards,

Diego

  • 0
    TI__Mastermind 36043 points

    Hi Diego,

    Are you able to share more context as to why you are not planning on using a 20 kOhm resistor?  20 kOhm has been characterized across PVT and is known to work.

    Please also see excerpt from data sheet below.

    Changing from 20k to 22k changes nominal pin voltage from 0.33*V_IN to 0.37*V_IN.  Given that the threshold is 0.5 * V_IN, this seems like a good margin, but has not been characterized.

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    Prodigy 140 points

    Hi Drew,

    Thank you for your response and for providing the clarification.

    The reason I am considering not using a 20 kΩ resistor is to achieve cost savings by standardizing to a smaller E-series for resistors across the design.

    I understand that typical IC internal resistances and thresholds can vary due to manufacturing and environmental factors.

    Therefore, if there is data available regarding variations in internal resistance or threshold values, I believe it would help ensure that the design is robust enough to accommodate the impact of the proposed change to 22 kΩ.

    Your feedback and any additional insights would be greatly appreciated.

    Best regards,
    Diego

  • +1 in reply to Diego Shinji Kawaguchi
    TI__Genius 9209 points

    Hi Diego,

    Although, we do not have specific data on the tolerances of the resistors it can be assumed based on the datasheet that the internal thresholds stay at the roughly the levels mentioned above across manufacturing and environmental factors.

    Best,

    Nick

  • 0 in reply to Nick Peabody
    Prodigy 140 points

    Hi Nick,

    Thank you for your prompt response and for clarifying the internal threshold tolerances.

    Your input has been helpful and is greatly appreciated.

    Thank you again for your support.

    Best regards,
    Diego