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BOOSTXL-DRV8305EVM: Could this Evaluation module be mis-wired?

Michael Banak
Intellectual 915 points
Part Number: BOOSTXL-DRV8305EVM

I need a buddy-check on a seeming error in the schematic of the BOOSTXL-DRV8305EVM.

The wiring error is verified by me in 4 places:

1) Page 11 of the user guide, SLVUAI8A

2) The PDF schematic, which comes with the design files: MDBU003A_SCH.PDF

3) and the Altium Schematic, which comes with the design files.

4) Even the application block diagram in the data sheet

Please look at the connection of the current sense connections, associated (for example) with the Dual MOSFET driver, for MOT_A

Look at the Isense connections, near ground.

SN1 (which is described as "Current amplifier negative input") is attached to the high side of the Isense resistor

SP1 (which is described as "Current amplifier positive input") is attached to GND, the low side

The description of these pins suggests that you have the wiring backwards.

==> How did you get this to work?

==> What am I getting wrong?

Please clarify, as my layout is in-progress.

  • 0
    TI__Mastermind 19720 points
    Hi Michael,
    You are correct in that that is a little strange way of connecting the SN and SP but is still a valid way of sensing the current through the resistor. The Sense amp output voltage with no voltage difference across the sense resistor will be VREF/2. If you connect the high side of the sense resistor to the SP pin then the sense amp will increase the voltage output when the current increases through the resistor. If you connect the high side of the sense resistor to the SN pin then the sense amp will decrease the voltage output when the current increases through the resistor. This means that either method is a valid way of connecting the circuit. The only difference is that you must compensate for the voltage shifts and what it means for the current in you motor control code.

    Regards,
    Michael
  • 0 in reply to Michael.Walker
    Intellectual 915 points

    Thank you for your generous reply. I have compared your remarks to the formulas in the data sheet, and I am now enlightened.

    I will count this issue closed.

    Most gratefully,

    Michael A. Banak