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Output voltage of LMC7101-Q1

Masami Michino
Genius 5070 points

Dear, All

The customer is examining LMC7101-Q1.
Vo value of "OUTPUT pin" becomes the point.
Conditions:
"V-=0V" and "V+=5.3V"
Rl=10kOhm
Full temperature range
More than output voltage 4.975V

However, it became the following voltage when calculating by the formula indicated to "RAIL-TO-RAIL OUTPUT" of the datasheet.
Output voltage 4.935V
About 40 mV runs short.
This is concerned with whether it is adopted or not.
I want you to calculate the detailed output voltage by a simulation etc.

Thanks, Masami M.

  • 0
    TI__Expert 7240 points

    Hello,

    I have assigned the appropriate apps engineer to look at your question.  He should get back to you within a few days.

  • 0 in reply to Ben Hopf
    Genius 5070 points

    Hi, Ben-san

    Thank you for having an engineer assigned

    Thanks, Masami M.

  • 0
    TI__Mastermind 49916 points

    Hello Masami,

    5V to 5.3V will make very little difference in the overall drive capability, maybe a few millivolts..

    Remember that the output swing numbers in the table are to Vs/2, which results in half the current. I am assuming your load is returned to V-.

    5V/10K=500uA. According to Fig.19, the output drop will be 30mV, so 5.3V - 30mV = 5.27V at room.

    Worst case output swing is at 125°C.

    We do not have test data for a 10K load, but the 2K maximum drop was 142mV (126mV average) at 125°C. For the 2K load, the difference was a 30% drop between the 25°C and 125°C numbers. Using the worst case 2K numbers, which would be even more worst-case for 10K, we can estimate the output swing.

    So 30mV + 30% = 39mV, which allows a swing of 5.3V - 39mV = 5.27V over temperature at 500uA (10K).

    You should easily be able to meet the 4.935V minimum spec. But remember that these numbers are not guaranteed.

  • 0 in reply to Paul Grohe
    Genius 5070 points

    Hi, Paul-san

    Thank you for your reply.
    Please let me know one.
    Is it a Typ. value although it is 39 mV of drops voltage? Or is it a max. value?
    I would like to know the maximum of drops voltage.
    In the case of a typ. value, it is from the following ideas?
    From "5V AC Electrical Characteristics" value, they are the conditions of Rl=2kohm and Vs=5V,
    The value of Typ. is 0.1V.
    The value of max is 0.3V.
    From this, a max value is calculated with 3 times of a typ. value.
    Ta = since the drops voltage at the time of 125℃ and Vs=5.3V is 39 mV, it triples, and it is 117 mV.
    The min. value of OUTPUT at the time of Vs=5.3V is 5.18V.
    Is this right?

    Thanks, Masami M.

  • 0 in reply to Masami Michino
    TI__Mastermind 49916 points

    Hello Masami,

    I went back and looked at the original characterization data. The 142mV was the maximum value of the lot at 125°C at 2K, so I used it as worst case. The average was 126mV at 125°C. A "typical" would have been from the 126mV average value.

    So the 39mV would be the extrapolated maximum at 125°C.

    The datasheet BOLD over-temp numbers are "padded' with guard bands and are worst case. If you want to "pad" the number by 3x to be safe, then the max swing would then be 5.18V, which is still well above your requirement.

    Again, any numbers not in the datasheet are not guaranteed. The numbers I am giving you are are for design guidance only and are not a guarantee.

    Regards,

  • 0 in reply to Paul Grohe
    Genius 5070 points

    Hi, Paul-san,

    Thank you for your reply.
    I answer it to a customer.

    Thanks, Masami M.