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INA139: Current Sense Resistor Placement & Routing Guidelines

Ponnusamy M
Prodigy 80 points
Part Number: INA139

Hi,

Our design uses INA139 for sensing currents around 80-100A.

For the current sense resistor, we are using multiple (3 Nos) resistors in parallel.

Pl share the placement & routing guidelines for the application which uses multiple resistors in parallel.

PFA screenshot of the schematics, FYR.

Best Regards,

Pons

  • 0
    Guru 140200 points

    Hi Ponnusamy,

    when using more than one shunt in parallel, the copper trace impedances between the shunts and the solder joint impedances of shunts can add considerable errors, which eventually would have to be calibrated out in software later. Keep in mind that the solder joint impedance can be up to 0.1...1mR, which is in the range of your shunt resistance. This can also result in heavy board to board variations.

    That's why I would use only one shunt and why I would connect it as shown in section 10.2 of datasheet. There, a four terminal shunt is shown which offers the best precision.

    Kai

  • 0 in reply to kai klaas69
    Prodigy 80 points

    Hi Kai,

    Thanks for the review of our design and feedback.

    We are leveraging an existing design of our customer hence we may have to retain multiple resistors.

    Is there a guideline available from TI which can be referred for this application?

    Best Regards,

    Pons

  • 0 in reply to Ponnusamy M
    TI__Expert 4720 points

    Hello,

    Kai is correct in his statements. The solder cannot be removed but understanding it and knowing the impact it could have can help you understand board to board variation. We currently do not have anything available for parallel sense resistors.

    Regards,

    Castrense