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TMCS1123: TMCS1123 - Impacts of expanding IN+/IN- copper flood beneath part

Part Number: TMCS1123

Other than voltage isolation, are there any issues with routing copper planes carrying current beneath the TMCS1123 part? We are looking at expanding the copper flood beneath the part (connected to IN+/IN-) to reduce voltage loss and we don’t require the full high voltage isolation separation. We just want to ensure that running any current below the part will not impact the sensitivity of the hall effect sensor or internal analog circuits. There is no mention in the datasheet of a keep out area other than for high voltage seperation.

Thank you

  • Hello Peter,

    If you do not need the voltage isolation spec, then this is generally fine to do. The only other potential concern that I can think of would be any magnetic filed generated from high current under the part, if that produced a magnetic field in the same direction as the internal Hall sensors. The TMCS1123 does have ambient field rejection, but there is still some error due to external field:



  • Hi Mitch - would that CMFR value be affected by running current carry copper from Pins 1 and 2 further beneath the part closer to pins 3-10? Or is that figure assuming no current flow in those areas?

    Thanks again,


  • Hey Peter,

    The specification for CMFR is independent of trace layout. It is simply for stray magnetic field present at the sensor. I do not expect that there would be much affect from extending the traces back on on pins 1 and 2.