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INA826 Datasheet Inconsistency

DMor
Intellectual 510 points
Other Parts Discussed in Thread: INA826, INA188

Hello, I'm working with the INA826. The documentation on Section 6 (Pin Configuration - Page. 4 shows the pin functionality and position on the 8-pin IC. On Section 11.2 (Layout Example) - Page. 35 it shows an example of laying out the IC and connecting its components. It appears that the layout is inconsistent with the pin positions mentioned in the first section. IE: The layout example diagram shows the same IC, but the pins are in a different position. Which is actually correct? Is this a mistake?

  • 0
    TI__Guru* 93105 points

    Hello DMor,

    Good catch! The PC board layout example in section 11.2, Fig. 73, is incorrect. That layout is actually for many of our older INA amplifiers. The pin configurations shown in section 6, page 4, are correct for the INA826.

    I will inform our Marketing Engineer of the error and he will need to get it in the datahseet correction queue.

    Regards, Thomas

    PA - Linear Applications Engineering

  • 0 in reply to Thomas Kuehl
    Prodigy 180 points

    Hello, Thomas!

    INA826, Datasheet, Page 17, Figure 56.

    Output impedance for 1Hz is 40 kOhm. Is it correct? Why so mutch? (INA188 - 5 Ohm).

    Thank You

    Andy

  • 0 in reply to Andy Brus1
    TI__Guru* 93105 points

    Hi Andy,

    Indeed the open-loop output impedance (Zo) across frequency is very different for the INA826 and the INA188, but that shouldn't really be an issue in most cases. The Zo is mostly dependent on the output stage design, the current through the output stage and whether their is internal feedback from the output stage to a preceding stage. The INA826 utilizes a CMOS drain output design that results in that kind of Zo response vs. frequency response seen in the Fig. 56 graph.

    The Zo of the INA826 difference amplifier stage is on the order of 40 kOhm at 1 Hz, but realize that when the loop is closed that closed-loop output impedance ZOUT is very low. For example, if the stage open-loop gain (Aol) is 120 dB (1e6 V/V), the approximate ZOUT will be about 40 milliohms. A similar calculation can be made for the INA188. 

    Regards, Thomas

    PA - Linear Applications Engineering