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TPS25980: Motor Drive Application

Visaacan Rathiraj
Prodigy 60 points
Part Number: TPS25980

Hi,

Currently looking to use the TPS25980 for protection to one of our motor driver boards
For our application when the system is powered off (TPS252980 in shutdown mode but power still applied to Vin) we allow the users to be able to back drive our motors
Due to this the voltage on VOUT rises until the body diode off the mosfet conducts. Based on some experiments the delta between vin and vout(vout-vin) during shutdown and back driving is 0.6V(assuming this is the forward voltage of the body diode)
In the data sheet it states that vout max is equal to Vin+0.3V. I am wondering is this parameter when the efuse is in the on state?
Do you see this as a concern if we allow the users to backdrive the motors causing the delta between vout and vin to be 0.6V?

Thank you for your help,
Visaacan

  • 0
    TI__Genius 11925 points

    Hi Visaacan,

    I will get back to you in some time.

    Best Regards,
    Arush

  • 0 in reply to Arush Gupta
    TI__Genius 11925 points

    Hi Visaacan,

    In our eFuse main passFET, body diode cannot sustain continuous current flowing through it and will reduce the life of main passFET. Since this device is not a reverse current blocking device, what happens during reverse current flow is, the device will allow some current transient to flow through the body diode. That transient will charge the input side capacitor and once the vin charges above UVP threshold (around 2.5V), the device main passFET turns on and the continuous current flow happens through the FET.

    Best Regards,
    Arush

  • 0 in reply to Arush Gupta
    Prodigy 60 points

    Hi Arush,

    Shouldn't the body diode be able to handle some continuous current? In this application we will not be directly applying a source on the VOUT pin it is just the voltage generated at very small moments of time by manually rotating the motor coils currents will be in the magnitude of 0.05A to 1A for very short periods

    Also in our application VIN is directly tied to a battery, so the VIN caps are always charged, and the current from flowing through the body diode would be going right to battery

    Our EN/UVP is not connected to VIN and only enabled when the system is turned on so the passFET will not turn on during reverse currents through the body diode

    I am wondering would this still reduce the life of the passFET considering the currents flowing through the body diode is about 10% of the capable current of the passFET

    Let me know what you think,
    Visaacan


  • +1 in reply to Visaacan Rathiraj
    TI__Genius 11925 points

    Hi Visaacan,

    They are not designed with continuous current through them in mind. 

    Visaacan Rathiraj said:
    it is just the voltage generated at very small moments of time by manually rotating the motor coils currents will be in the magnitude of 0.05A to 1A for very short periods

    So, the back current is for very short duration of time, am I correct? If the power dissipation at body diode is not much and is only for short duration, then the body diode won't get damaged.

    Best Regards,
    Arush

  • 0 in reply to Arush Gupta
    Prodigy 60 points

    Great thank you for the clarification