In our application we have two modes of vehicle operation: manual and autonomous. Meaning that when vehicle is operated autonomously we control a brushed DC-motor using an H-bridge. In manual mode we don't control it, DC motor will see high impedance on its leads and can be backdriven. So in manual mode we want as less resistance as possible to backdrive the motor and we want to protect our circuitry from charge generated by the motor and the motor itself. Is there a common practice for that?
Below is the relevant part of the circuitry that we are going to use to drive the motor, it consists of a gate driver and an H-bridge.
Best Answer
Basically you need a diode in series with the supply to the motor -- that will prevent the motor from supplying power back to the supply.
Trouble is the diode will drop 0.7 V and will dissipate power -- you can use a MOSFET in the supply or GND connection and drive it on when the motor is on, and off when the motor is off. You'll have to connect that FET with drain & source backwards from normal usage.