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TPL0401A-10-Q1: Configuration of TPL0401 as a Variable Resistor with INA823

Shah Zaman
Prodigy 90 points
Part Number: TPL0401A-10-Q1
Other Parts Discussed in Thread: INA823

Tool/software:

Hello,

I am currently using the INA823 instrumentation amplifier and want to adjust its gain dynamically using an MCU. To achieve this, I plan to connect a TPL0401 digital potentiometer configured in rheostat mode as a variable resistor.

Question 1: When configuring the TPL0401 in rheostat mode, should I connect the wiper (Pin 5) to ground, or leave it unconnected? I am concerned that a floating wiper would create an unwanted voltage divider, complicating the gain adjustment process.

Question 2: I need to connect Pin 1 of the INA823 to Pin 6 on the TPL0401, and Pin 8 of the INA823 to GND (Pin 2) of the TPL0401. Additionally, I plan to supply VDD to Pin 1 of the TPL0401. Where should I connect the ground of the power supply, given that GND is already connected to the INA823?

Thank you for your assistance!

  • 0
    TI__Mastermind 41503 points

    Hi Shah, 

    In rheostat mode you should connect the two resistor terminals to either W and GND or W and H. The unused terminal can be left floating or connected to the wiper. Leaving them floating will not create a resistor divider. It looks like you were trying to use H and GND and leave the wiper floating. In that case you would always see the full end-to-end resistor value instead of a variable resistor. Here's a description of rheostat mode from a similar device datasheet. 

    Also connect the GND of the power supply to the TPL0401. All grounds in the system should be connected. 

    Best,

    Katlynne Jones

  • 0
    TI__Mastermind 41503 points

    Hi Shah, 

    You do not use H and L for a rheostat; else you would be seeing the full end-to-end resistance no matter what code you send. 

    In rheostat mode you should connect either W and GND or W and H across the INA. The unused terminal can be left floating or connected to the wiper. The GND terminal should always be connected to ground. Assuming you do not want one of the INA terminals grounded, you can use W and H, 

    Best,

    Katlynne Jones

  • 0 in reply to Katlynne Jones
    Prodigy 90 points

    Thank you  for assistance