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INA220: VBUS connection for High side sensing

JAGADISH K
Prodigy 10 points

Part Number: INA220

I have a requirement wherein I have to measure a 12V that powers stepper motor ICs, the current can range from a few milliamps to 1.5A. Since the stepper motor IC has internal H bridges and I had to do high-side current sensing, so I settled upon INA220 IC.
Following are my queries (Please refer to the attached reference Image ) - 

  1. What junction should the VBUS be connected to, IN+ or IN-, and what is the role of the VBUS connection in each case? I have seen in the datasheet it's connected to IN+ or IN- in different instances.
  2. What would be the apt Sense resistor in this case(5mA - 1.5A)?
  3. I have attached the schematic and Layout snips, I'd appreciate some feedback or corrections if necessary.

Reference Image 

https://drive.google.com/file/d/19o2zdJkyt293MgJXHPLxF0jMsP_Mh4XA/view?usp=share_link

  • +1
    TI__Expert 6602 points

    Hi Jagadish,

    1. VBUS can be connected to either IN+ or IN-, it just depends if you want to factor in the power consumption from the INA220 in the power calculations. If you connect VBUS to the IN-, it will not include the drop across the resistor. Both designs are valid. 

    2. There are various aspects to choosing the appropriate sense resistor such as power, size, and current levels. You may use our power monitor tool to help with that: www.ti.com/.../01.00.00.00

    3. The circuit and layout looks mostly fine. The input filtering is optional, but if you intend on filtering IN+ and IN-, then be sure to use filtering resistors of 10ohm and a ceramic capacitor of 0.1uF to 1uF: 

    One note on the layout, we recommend using kelvin connections to the sense resistor as seen here: 

    Best,

    Mohamed 

  • 0 in reply to Mohamed Hamida
    Prodigy 10 points

    Hi Mohamed,

    Mohamed Hamida said:
    One note on the layout, we recommend using kelvin connections to the sense resistor as seen here: 

    I did follow the Kelvin method, Please let me know if it needs additional changes.



    Regards,
    Jagadish

  • 0 in reply to JAGADISH K
    TI__Expert 6602 points

    Hi Jagadish,

    My apologies, I seem to have missed that. All looks well!

    Best,

    Mohamed