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INA281: Use current sense IC für DCR current sensing

Marcel Klose
Prodigy 80 points
Part Number: INA281
Other Parts Discussed in Thread: TPS65311-Q1, INA240

Hi there,

is it possible to use this or another IC for "DCR current sensing" over an inductor after a half bridge? Something like this:

"TPS65311-Q1 BUCK1 Controller DCR Current Sensing" (SLVA791)

it's a little bit like peak current sensing, only for better unterstanding.

We already have a digital controller, so we only need the signal.

Best regards

Marcel

  • 0
    TI__Mastermind 29810 points

    Marcel,

    I will need to look at the document as I am not familiar with it but just skimming through it.  The thing I worry about it the AC CMRR and Bandwidth with respect to input voltage and the negative recovery when Vsense <0.  I have attached snap shots of the spots in the datasheet.  

    For AC CMRR you can see the CM input to the Device is like a step function meaning it has high frequency components.

    Bandwidth-The bandwidth is not constant with your input Vsense and this could cause issues as the switch is going from low to high current.  This is less and an issue as the inductor should have current during the times of concerns but realize the bandwidth does change.

    Vsense <0.  This could be a transient and could place the device in a state that can cause issues as the input of Vsense can temprarly can go below Zero.

  • 0 in reply to Javier Contreras4
    TI__Mastermind 29810 points

    Adding the snapshot from datasheet.

  • 0 in reply to Javier Contreras4
    Prodigy 80 points

    Hi Javier,

    thanks for response. Yeah you are right. Unidirectional is the value I missed. But INA240 is bidirectional? And it's also quite fast with 400 kHz.

    What do you think?

    Best regards

    Marcel

  • 0 in reply to Marcel Klose
    TI__Mastermind 29810 points

    Hello Marcel,

    I believe that would be a better option and it has the PWM rejection which will help with the switching conditions.

    Regards,