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TL7705B: Resistor Tolerance

Jacob Olstad
Intellectual 1260 points
Part Number: TL7705B
Other Parts Discussed in Thread: TL7715A, , TPS3700, TPS3702, TPS3701

Hi,

We use the TL7705B to monitor a couple of 5V rails and would like to adapt it to monitor a 15V rail (the TL7715A doesn't have the needed temp range for us and we already use the TL7705).

We would add a series resistor to the 15V rail into the sense input of the part.  I've seen datasheets for this part that state that R1 and R2 in the sense resistor divider are 23Kohms and 10Kohms respectively, is this accurate?  The datasheet on TI.com doesn't have a note 1 as the resistors call out.  

I also want to understand the tolerance on the resistors.  The electrical characteristics table trip tolerance gives some idea of how they vary in relation to each other but not their absolute tolerance.

Regards,

Jake

  • 0
    TI__Genius 12630 points
    Jake,

    I pulled old datasheets for TL7705B and you are correct, R1 = 23kohm and R2 = 10kohm, nominal. We do not provide tolerances for these resistors and any application that use this device above the recommended operating conditions should be tested thoroughly. I have seen successful applications using either a series resistor or even a Zener diode to clamp the input voltage, but my recommendation is to use a newer device with 15V+ capability that has been thoroughly tested and guaranteed by TI. The device family I recommend is TPS3700, TPS3701 and TPS3702 devices which have 18V and 36V capability.

    We will work to correct the current TL7705B datasheet to add the resistor note back in, but we do not specifically guarantee the resistor tolerance but only guarantee the device accuracy.

    I hope this helps you! Let me know if you have any other questions. Thanks!

    -Michael
  • 0
    Guru 140200 points
    Hi Jacob,

    allthough the ratio of these both resistors might be precise, the absolute values can have huge tolerances. You should expect a double-figure percentage rate.

    Kai