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INA250: INA250: Current sensor for inductive loads (motors and solenoid coils)

Cody Bertetto
Prodigy 60 points
Part Number: INA250
Other Parts Discussed in Thread: DRV8823, , INA260, INA253, INA240

Hello,

I'm looking the proper external current sensor to work with the DRV8823 motor drive for overall diagnostics (motor open, motor stalled or peak current, motor shorted, etc.).  The voltage for driving the bi-directional motors and solenoids will be 0 to +12VDC PWM.  I have really been looking at the INA260 and INA250.  INA260 is nice because of the digital interface, but the sampling frequency is a maximum of 3.5kHz.  The INA250 sampling frequency ranges from 11 to 50 kHz, which seems more suitable for a PWM motor signal.  The current sensor is not being used for the control loop overall, but is just being used for diagnostics.  Both the INA250 and INA260 show the absolute maximum common mode voltage range of GND-0.3V to +40V.  The GND-0.3V is the hard one to protect against is seems.  I know the DRV8823 already has the flyback diodes to protect itself when the inductive load (bi-directional motor or solenoid) is turned off, but I'm not sure if the INA250 or INA260 would be able to handle it the switching off of the inductive load.

I can put a schotty diode or a TVS to ground on both the IN+ and IN-, but the forward voltage bias of most diodes is 0.5V or higher (greater than the -0.3V per INA250 and INA260).  Do you have any recommendations on how to protect the INA250 or if it is even required?  Or do you have any other recommendations to monitor the current?

Thanks,

Cody

  • 0
    TI__Mastermind 26335 points

    Hello Cody,

    Thanks for considering to use Texas Instruments in your design.  We typically do not recommend the INA250 for fast PWM signals in high-side or inline applications  as covered in this thread.  If you can afford to have a little larger footprint, I would recommend the INA240 with an external shunt resistor.  However, if you absolutely need a device with an integrated shunt and can wait a little, INA253 would be a good alternative.  INA253 samples are available right now and the total official release is projected to be in about a month. Both the INA240 and INA253 will give you a little more headroom for the lower common mode voltage bound.

    Assuming you decide to stick with the INA250 or simply would still like to be aware of other methods to protect devices with a -0.3V limitation, this thread has a few additional methods aside from your proposed TVS diodes.