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ADM1270

Category: Hardware
Product Number: ADM1270

Hi Team,

Can we use AD74413R EVM for inductive loads?

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  • Hi  ,

    In short yes, inductive loads can be used, however special attention needs to be paid to potential hazardous high voltage spikes or ringing, which may damage the part. 

    It needs to be ensured that at all time, voltage at the AD74413R pins won't exceed +-50V. (As per ABSOLUTE MAXIMUM RATINGS table in the datasheet.) 

    These Voltager spikes are typically clamped by TVS, as per recommended channel circuit. Attention needs to pay in picking correct TVS to suit your requirements. 

    If you are driving inductive loads using AD74413R current output, it is advised to configure slew rate.

      

    Regards,

    Arnost

  • Hi  ,

    Thanks for the information.

    As you are already aware, an external power switch IC (ADM1270) is used for digital outputs in the AD74413EVM.

    we have used the 12W solenoids as a inductive load (24V/500mA) and connected to the EV-AD74413RSDZ module (Current limit set to 600mA).

    When the digital  output is turned off, output is going to negative voltage.

    If you see this, its apparent that the system is intentionally driving the -47V.

    With external Driver ADM1270 do we still need to use the below 

  • HI  ,

    in your case you are driving solenoid by ADM1270.

    This means, there is no need for slew rate limitation of the AD74413R. Recommendation for Slew rate setting is only once you use Iout (25mA max.) function of AD74413R to drive inductor.

    Regards,

    Arnost 

  • Hi  ,

    Yes, we are driving solenoid (24V/500mA) by ADM1270(Current limit set to 600mA).

    When the digital output is turned on and off, output is going to negative voltage during off condition.

    If you see this, its apparent that the system is intentionally driving the -47V.

  • Hi  ,

    Plot you have shared is expected, as the negative voltage spike (-47V) is solenoid commutation. Once the switch is turned off magnetic field of the inductor/solenoid is trying to sustain the current. TVS is clamping it before reaching -50V, which have to be always ensured, as per AD74413R Maximum absolute ratings.

    Perhaps let me clarify again: in such condition there is no need for slew rate limitation at AD74413R.

    I hope this brings you clarity.

    Feel free to reach out to me, if you would need more information. 

    Regards,

    Arnost 

  • Hi  ,

    We have added freewheeling diode (1N4148W-13-F)to  prevents the load voltage from becoming negative.

    It will have an impact on other configuration features, such as the analog voltage input/voltage output, analog current input/current output ?

  • Hi  ,

    I was checking the configurations, and freewheeling diode should not have impact on other configurations of AD74413R.

    I was also considering that it might be advantageous for you to use Uni-directional TVS. It will operate as TVS in one direction and when forward bias, it should act as diode. (This might help you to save BOM count). However, I find it challenging as TVS I was looking at, didn't have much specification when forward biased.

    Regards,

    Arnost

Reply
  • Hi  ,

    I was checking the configurations, and freewheeling diode should not have impact on other configurations of AD74413R.

    I was also considering that it might be advantageous for you to use Uni-directional TVS. It will operate as TVS in one direction and when forward bias, it should act as diode. (This might help you to save BOM count). However, I find it challenging as TVS I was looking at, didn't have much specification when forward biased.

    Regards,

    Arnost

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