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INA138 - Resistor load and stability

MGranzotto
Prodigy 20 points

Other Parts Discussed in Thread: INA138

Hey TI Community,

Im developing a boost converter as a learning experience, and I intend to use INA138 to measure my inductor current, with variable gain set by a potenciometer and then buffered by an opamp.

From the datasheet, it seems that RL is expected to be tied close to the pins:




Is this required for stability? Could I for example have RL far from the IC and close to the buffer?

  • 0
    TI__Expert 4595 points
    Hi,Can you please share your schematic.
  • 0 in reply to Rabab Itarsiwala
    TI__Genius 14825 points

    We don't have any examples or experiments with the load resistor placed a distance away from the device.  Because it is a current-output device, it will probably be somewhat immune to voltage drops over the length of the wire, and also it doesn't have a maximum load capacitance for stability listed in the spec table.  We have a prototype EVM available that we could send you if you want to try your own experiments with it.  I'm not sure if you want to have the potentiometer attached on the same PCB or on an adjacent PCB through a cable, or just fly-wired to a potentiometer, but this could perhaps let you try it out and build some confidence.


    What's the end application you're working on?

    If you would like a prototype EVM, please share your address with me at bridgmon_jason@ti.com.

  • 0 in reply to Jason Bridgmon
    Prodigy 20 points

    Thank you for the reply. I appreciate the offer but there's no need since i'm close to done with my project and asked more out of interest. 

    The end application is a boost converter using SMC control, with current state being fed for the controller. I'll stick to make the output of the current monitor and apply my variable gain on the next stage.