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DRV8343-Q1: Current Sense Amplifier Calibration

Shinichi Yokota
Genius 9715 points
Part Number: DRV8343-Q1

Hello,

DRV8343-Q1 has two types of calibration for the current sense amplifiers - manual calibration and automatic one. I'd like to ask some questions about this function.

  • Are the specs of the CSA's "VOFF - Input offset error" the ones after the automatic calibration?
  • Is it correct to understand that the manual calibration requires voltage measurement at SOx pins?
    • And then, the system must store the value and use it to offset the CSA's VOFF?
  • If the answer to the above question is yes, I guess a residual input offset error depends on the measurement error. But, if ideally the measurement error is zero, how much can the residual input offset error be practically?

Best regards,
Shinichi Yokota

  • +1
    TI__Mastermind 26046 points

    Hi Yokota-san

    1) Yes, the input offset error is after automatic calibration
    2) Yes, this is the correct operation. Inputs of CSA are shorted to GND and SOx is measured to correct value (VREF/2), and a small offset is added to calibrate the correct SOx output. 
    3) A residual offset error would occur only over temperature, as CSA offset drift varies with temperature by 10uV/C typical. Automatic calibration helps removes this over at powerup or wake (after ENABLE = high), and calibrates all 3 CSAs. Manual calibration can be done during operation so offset is negligible for SOx outputs, which can be done by toggling the CAL pin, or in SPI devices, by setting CAL_MODE to 0b. Furthermore, SPI devices can calibrate each CSA individually, so if a phase is Hi-Z, you can perform CSA calibrations so the CSAs are always calibrated. 

    Thanks,
    Aaron