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DRV8231A: Current flowing through VM Body Diode

Jennifer Jordan
Intellectual 1076 points
Part Number: DRV8231A
Other Parts Discussed in Thread: DRV8837,

Hello, 

I saw this kind of question posted for DRV8837 here but wanted to check if the same would be true for DRV8231A.

Application: AC pile charging inlet lock

Issue: 

Customer need unlock their charging plug when charging pile power down, so they connect a capacitor to the negative terminal of the motor.  When the system is powered off, the switch is closed and the capacitor is discharged to drive the motor to rotate. But the current will also flow into VM through body diode, the reverse current will turn on LDO and repower other ICs. This is what the customer doesn't want. Do we have any solution about this issue?

  • +1
    TI__Mastermind 21135 points

    Hey Jennifer,

    All BDC motors become a dynamo (DC generator) when they are rotated mechanically and all MOSFETs come with a body diode inherently. So this phenomenon will be observed with any H-bridge driving a BDC including external MOSFETs based H-bridge. VM terminal will "see" this generated voltage when it is not powered up. An ideal diode (or a regular diode) in series to the supply coming in to the VM pin can help isolate this voltage from driving other circuits such as an LDO on the same rail. However this cannot prevent from the DRV itself getting temporarily powered up by the BEMF. Customer must ensure this generated voltage does not violate the abs max spec. for VM of the DRV. A Zener diode (power Zener) to GND from VM could help mitigate this voltage from exceeding the limit. Below figure is an example. Have a great 2024! 

     

    Regards, Murugavel