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Spec questions about OPA2365AQDRQ1

Michael McDermott
Prodigy 10 points

Other Parts Discussed in Thread: OPA2365, OPA2320

www.ti.com/.../opa2365.pdf
The datasheet has conflicting information. In the description (and on website summary) it says 125C, but under Absolute Maximum Ratings and Recommended Operating conditions, it says 150C max.

Also, 

dVos/dT: How can I calculate worst case input offset voltage over temp, when given only nominal value
Figures 5 and 6 show typical bias current vs temp and typical bias current vs common mode voltage. How do I determine worst-case behavior at a particular bias voltage and temperature?

Thanks

  • Guru 140200 points

    Hi Michael,

    while the OPA2365 withstands temperatures up to +150°C, all the data is specified up to +125°C only. This is no contradiction to me.

    Figures 4, 5 and 6 will help to estimate worst case data.

    What is your temperature range of application? What is your common mode input voltage range?

    Kai

  • in reply to kai klaas69
    Prodigy 10 points

    Our max board temp is 105C and common mode input voltage can approach 5V.

  • in reply to kai klaas69
    Prodigy 10 points

    So the input bias current is specified at 10pA. Figure 5 shows that the nominal is about 0 up to 50 degrees and exceeds 600pA at 125C.  So what is a worst-case unit at 125C? Is it 6000pA (Assuming nominal is 1pA, at 25C, but worst-case of 10pA)

    Figure 6 shows bias current vs common mode voltage. This can approach 500pA at 5V. Again, so I assume 10x of this or 5000pA at 5V?

    What about bias voltage and temperature? Are the effects additive or multiplicative? If I multiply the effects I calculate 10pA*600*580 = 3.5uA Is this correct?

  • in reply to Michael McDermott
    TI__Mastermind 31845 points

    Hello Michael,

       For offset voltage, you can use Figure 3 and 4 to determine the distribution and the max offset voltage and offset voltage drift as well as range allowed for our lots. So max offset voltage is 200uV at 25C and max offset voltage drift is 5uV/C. So at 105C, the max offset voltage is around 600uC.

       For input bias current, I would not commit to saying it is a linear trend, I will have to check on this and get back to you.

       For bias voltage + input bias current over temperature, the offset voltage would be seen at the output of the amplifier (changes with temperature) with the addition of bias current * resistance (also changes with temperature).

    Thank you,

    Sima

       

  • in reply to Michael McDermott
    Guru 140200 points

    Hi Michael,

    have you thought about using the OPA2320? The OPA2320 comes with tighter toleranced input bias currents.

    Kai

  • in reply to Michael McDermott
    TI__Mastermind 31845 points

    Hello Michael,

       Sorry on the delay for the input bias current information. Still working on getting internal access to some folders, and will get back to you by end of this week.

    Thank you,

    Sima

  • in reply to Michael McDermott
    TI__Mastermind 31845 points

    Hello Michael,

      Unfortunately, we do not have a figure on max input bias current vs temperature. 

    Thank you,
    Sima