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INA4230: INA4230 suitability for bidirectional motor current sensing with reversed input polarity

Hori Shota
Expert 1425 points

Part Number: INA4230

Hi team,
 
Purpose
I would like to confirm whether INA4230 can be used for sensing bidirectional motor current.
Background / Setup
  • Device: INA4230
  • Application: Motor current sensing
  • The motor rotates in both directions, so the current direction through the shunt resistor reverses depending on rotation.
Issue / Question
When the motor current reverses, the polarity across the shunt resistor also reverses.
In this condition:
  • Can INA4230 still be used as a current-sense amplifier?
  • Is it acceptable if the polarity between IN+ and IN− is reversed due to current direction?
  • Are there any functional limitations or accuracy concerns when IN+ becomes lower than IN−?
I would like to understand whether bidirectional current measurement is supported and what conditions must be met.
 
Best Regards,
Shota
  • +1
    TI__Genius 9880 points

    Hi Shota,

    Yes — the INA4230 fully supports bidirectional current sensing.

    The device is designed to measure differential voltages in both polarities across the shunt resistor, so it will work correctly when motor current reverses direction.

    Bidirectional Capability

    The INA4230 supports programmable full-scale differential input ranges of ±81.92mV or ±20.48mV across the IN+ and IN− pins, selectable via the RANGE field in the CONFIG2 register. The ± designation explicitly means the device handles both positive and negative differential voltages — when your motor reverses and IN+ drops below IN−, the device simply reports a negative shunt voltage (and correspondingly negative current value). No special configuration is needed beyond normal setup.

    Accuracy When Polarity Reverses

    There are no accuracy degradations or functional limitations when IN+ becomes lower than IN−. The integrated 16-bit delta-sigma ADC maintains the same specifications regardless of current direction:

    Parameter

    Specification

    ADC Resolution

    16-bit

    Gain Error

    0.75% maximum

    Offset Voltage

    75 µV maximum

    Input Common-Mode Range

    −0.3V to 48V

    The low 75 µV offset is particularly beneficial for accurate sensing at light loads in either direction.

    One Design Consideration: Power and Energy Registers

    While the current register is signed (captures direction), be aware that the power and energy registers are unsigned 16-bit and 32-bit values respectively. This means power and energy accumulate as absolute magnitudes without distinguishing current direction. If your application needs to track net energy flow (e.g., motoring vs. regenerative braking), you would need to handle that distinction in your firmware using the signed current value.

    Conditions to Meet

    1. Shunt voltage must stay within the selected full-scale range — ensure your maximum motor current × shunt resistance does not exceed ±81.92mV (or ±20.48mV if using the higher-resolution range).
    2. Common-mode voltage at IN− must remain within −0.3V to 48V throughout operation.
    3. No power-supply sequencing requirements — the bus common-mode voltage and VS supply are independent of each other.

    The datasheet even includes a design example with an ADC range selection of ±81.92mV and a 10A maximum current at 12V bus voltage, confirming the intended use for bidirectional applications.

    Best,
    Mallika Senthil